Digitala Vetenskapliga Arkivet

Change search
Refine search result
1234 1 - 50 of 180
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Abahazi, Emese
    et al.
    Satorhelyi, Peter
    Erdelyi, Balazs
    Vertessy, Beata G.
    Land, Henrik
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Paizs, Csaba
    Berglund, Per
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Poppe, Laszlo
    Covalently immobilized Trp60Cys mutant of omega‰-transaminase from Chromobacterium violaceum for kinetic resolution of racemic amines in batch and continuous-flow modes2018In: Biochemical engineering journal, ISSN 1369-703X, E-ISSN 1873-295X, Vol. 132, p. 270-278Article in journal (Refereed)
    Abstract [en]

    Covalent immobilization of an engineered omega-transaminase mutant Trp60Cys from Chromobacterium violaceum (CvTAW60C) was performed on bisepoxide-activated aminoalkyl resins. Activity of the various CvTAW60C preparations was evaluated in kinetic resolution of four racemic amines (rac-1a–d). The most active EA-G-CvTAW60C preparation (CvTAW60C attached to polymeric resin with ethylamine function activated with glycerol diglycidyl ether—EA-G) could perform the kinetic resolution of racemic 4-phenylbutan-2-amine (rac-1a) over 49% conversion up to 19 consecutive reaction cycles or in media containing up to 50% v/v DMSO as cosolvent in batch mode reactions. The immobilization process of CvTAW60C onto the EA-G resin filled in stainless steel bioreactors was also tested in flow-through mode. Kinetic resolution of three racemic amines containing aromatic moieties (rac-1a-c) was performed in continuous-flow mode resulting in easy-to-separate mixture of the corresponding ketone (2a–c) and the non-converted (R)-amine in high enantiopurity (ee(R)-1a-c ≥ 96%).

  • 2.
    Agnhage, Tove
    et al.
    University of Borås, Swedish School of Textiles.
    Nierstrasz, Vincent
    University of Borås, Swedish School of Textiles.
    Perwuelz, A.
    Guan, J.P.
    Chen, G.Q.
    Eco-design innovative methods for fabric finishing2014Conference paper (Other academic)
  • 3.
    Ahmed, Ajaj
    et al.
    Department of Microbiology, M.G.S. University, Bikaner, India.
    Dabi, Narendra Kumar
    Department of Microbiology, M.G.S. University, Bikaner, India.
    Verma, Swati
    Department of Microbiology, M.G.S. University, Bikaner, India.
    Gehlot, Praveen
    Department of Botany, J.N.V. University, Jodhpur, India.
    Purohit, Praveen
    Department of Chemistry, Engineering College, Bikaner, 334001, India.
    Kumar, Rajender
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Meghwanshi, Gautam Kumar
    Department of Microbiology, M.G.S. University, Bikaner, India.
    Evaluation of Thar Desert bacterial lipases for catalytic efficiencies and biodiesel production potentials2023In: Biologia, ISSN 0006-3088, E-ISSN 1336-9563, Vol. 78, no 4, p. 1187-1197Article in journal (Refereed)
    Abstract [en]

    The present work describes the screening of thermotolerant bacteria isolated from Thar Desert environmental samples for lipase activity and their catalytic efficiencies, such as tolerance to extreme pHs, temperatures, and organic solvents, and efficiency to synthesize biodiesel from waste cooking oils. The selected lipases were thermos-alkaliphilic in nature showing good activity at higher temperatures and in the alkaline pH range with optimal activity at 45 °C and pH 8 or 9. The lipases efficiently converted oils to biodiesel (fatty acid methyl ester), giving up to 78% conversion under specific reaction conditions. The enzyme (lipase) mediated biodiesel production will soon offer an eco-friendly and sustainable energy source for automobiles and industrial applications. The thermos-alkaliphilic properties of these lipases along with their efficiency to produce fatty acid methyl ester from waste cooking oil and methanol as well as other prospective applications, make them potential candidates for biodiesel production and other prospective applications such as the synthesis of flavor and fragrance esters and remediation of various environmental pollutants.

  • 4. Allas, Ular
    et al.
    Toom, Lauri
    Selyutina, Anastasia
    Maeorg, Uno
    Medina, Ricardo
    Merits, Andres
    Rinken, Ago
    Hauryliuk, Vasili
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). University of Tartu, Institute of Technology, Nooruse 1, Tartu 50411, Estonia.
    Kaldalu, Niilo
    Tenson, Tanel
    Antibacterial activity of the nitrovinylfuran G1 (Furvina) and its conversion products2016In: Scientific Reports, E-ISSN 2045-2322, Vol. 6, article id 36844Article in journal (Refereed)
    Abstract [en]

    2-Bromo-5-(2-bromo-2-nitrovinyl) furan (G1 or Furvina) is an antimicrobial with a direct reactivity against thiol groups. It is active against Gram-positive and Gram-negative bacteria, yeasts and filamentous fungi. By reacting with thiol groups it causes direct damage to proteins but, as a result, is very short-living and interconverts into an array of reaction products. Our aim was to characterize thiol reactivity of G1 and its conversion products and establish how much of antimicrobial and cytotoxic effects are due to the primary activity of G1 and how much can be attributed to its reaction products. Stability of G1 in growth media as well as its conversion in the presence of thiols was characterized. The structures of G1 decomposition products were determined using NMR and mass-spectroscopy. Concentration-and time-dependent killing curves showed that G1 is bacteriostatic for Escherichia coli at the concentration of 16 mu g/ml and bactericidal at 32 mu g/ml. However, G1 is inefficient against non-growing E. coli. Addition of cysteine to medium reduces the antimicrobial potency of G1. Nevertheless, the reaction products of G1 and cysteine enabled prolonged antimicrobial action of the drug. Therefore, the activity of 2-bromo-5-(2-bromo-2-nitrovinyl) furan is a sum of its immediate reactivity and the antibacterial effects of the conversion products.

    Download full text (pdf)
    fulltext
  • 5.
    Bashari, Mohanad
    et al.
    Asharqiah Univ, Oman.
    Ahmed, Hani
    Nanchang Univ, Peoples R China.
    Mustafa, Ayman Balla
    Misurata Univ, Libya.
    Riaz, Asad
    United Arab Emirates Univ, U Arab Emirates.
    Wang, Jinpeng
    Beijing Technol & Business Univ BTBU, Peoples R China.
    Saddick, Salina Yahya
    King Abdulaziz Univ, Saudi Arabia.
    Omar, Abdulkader Shaikh
    King Abdulaziz Univ, Saudi Arabia; Najla Bint Saud Al Saud Ctr Distinguished Res Biot, Saudi Arabia.
    Afifi, Mohamed
    Najla Bint Saud Al Saud Ctr Distinguished Res Biot, Saudi Arabia; Univ Jeddah, Saudi Arabia.
    Al-Farga, Ammar
    Univ Jeddah, Saudi Arabia.
    AlJumaiah, Lulwah Zeyad
    Univ Hail, Saudi Arabia.
    Abourehab, Mohammed A. S.
    Umm Al Qura Univ, Saudi Arabia.
    Belal, Amany
    Beni Suef Univ, Egypt; Taif Univ, Saudi Arabia.
    Khalifa, Mohamed Yassin Zaky
    Linköping University, Department of Biomedical and Clinical Sciences, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Oncology. Beni Suef Univ, Egypt.
    Fabrication and Characterization of Dextranase Nano-Entrapped Enzymes in Polymeric Particles Using a Novel Ultrasonication-Microwave Approach2023In: Catalysts, E-ISSN 2073-4344, Vol. 13, no 1, article id 125Article in journal (Refereed)
    Abstract [en]

    In the current study, a novel method to improve the nano-entrapment of enzymes into Ca-alginate gel was investigated to determine the synergistic effects of ultrasound combined with microwave shock (UMS). The effects of UMS treatment on dextranase enzymes loading effectiveness (LE) and immobilization yield (IY) were investigated. By using FT-IR spectra and SEM, the microstructure of the immobilized enzyme (IE) was characterized. Additionally, the free enzyme was used as a control to compare the reusability and enzyme-kinetics characteristics of IEs produced with and without UMS treatments. The results demonstrated that the highest LE and IY were obtained when the IE was produced with a US of 40 W at 25 kHz for 15 min combined with an MS of 60 W at a shock rate of 20 s/min for 20 min, increasing the LE and the IY by 97.32 and 78.25%, respectively, when compared with an immobilized enzyme prepared without UMS treatment. In comparison with the control, UMS treatment dramatically raised the Vmax, KM, catalytic, and specificity constant values for the IE. The outcomes suggested that a microwave shock and ultrasound combination would be an efficient way to improve the immobilization of enzymes in biopolymer gel.

    Download full text (pdf)
    fulltext
  • 6.
    Berglund, P.
    et al.
    University of Toronto, Canada.
    Stabile, M. R.
    Gold, M.
    Jones, J. B.
    Mitchinson, C.
    Bott, R. R.
    Graycar, T. P.
    Altering the specificity of subtilisin B. lentus by combining site-directed mutagenesis and chemical modification1996In: Bioorganic & Medicinal Chemistry Letters, ISSN 0960-894X, E-ISSN 1464-3405, Vol. 6, no 21, p. 2507-2512Article in journal (Refereed)
    Abstract [en]

    The thiol side chain of the M222C mutant of the subtilisin from Bacillus lentus (SBL) has been chemically modified by methyl-, aminoethyl-, and sulfonatoethylthiosulfonate reagents. Introduction of charged residues into the active site of the enzyme reduced the catalytic efficiency with Suc-AAPF-pNA as the substrate, but resulted in better binding of sterically demanding boronic acid inhibitors.

  • 7.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    BIO-AMINES: Searching for a Novel Approach to Biocatalytic Transaminations – a Vinnova Sponsored Project2009In: Book of abstracts, 2009Conference paper (Other academic)
  • 8.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Biocatalysis with Promiscuous Enzymes2007In: 2007 European BioPerspectives / [ed] Dechema, 2007Conference paper (Refereed)
  • 9.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Enzyme Catalytic Promiscuity and Rational Design2006In: Book of abstracts, 2006Conference paper (Refereed)
  • 10.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    omega-Transaminases: Tailored for Chiral Amine Synthesis2010In: Biocat2010 / [ed] Ralf Grote, Garabed Antranikian, Hamburg, Germany: TuTech Verlag , 2010Conference paper (Refereed)
  • 11.
    Berglund, Per
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Christiernin, M.
    Hedenström, E.
    Enantiorecognition of chiral acids by Candida rugosa lipase: Two substrate binding modes evidenced in an organic medium2001In: American Chemical Society Symposium Series (ACS), ISSN 0097-6156, E-ISSN 1947-5918, Vol. 776, p. 263-273Article in journal (Refereed)
    Abstract [en]

    We have identified the existence of different modes of binding the enantiomers of 2-methyl-branched carboxylic acids to a lipase active site by rational substrate engineering. Similar to hydrolysis, previously investigated, we have now evidence for differential binding modes in the Candida rugosa lipase-catalyzed esterifications in cyclohexane. The relevance of considering two different binding modes to understand lipase enantiorecognition is demonstrated by introducing bulky substituents on a chiral carboxylic acid which impose a different orientation of the substrate acyl chain in the active site of Candida rugosa lipase. With this substrate engineering approach based on molecular modeling it is thus possible to markedly alter the enantioselectivity of the lipase. Examples from hydrolysis and new results from esterifications in an organic solvent are presented and discussed.

  • 12.
    Berglund, Per
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hedenström, Erik
    Mid Sweden university.
    Preparation of 2-, 3-, and 4-methylcarboxylic acids and the corresponding alcohols of high enantiopurity by lipase-catalyzed esterification2001In: Enzymes in Nonaqueous Solvents: Methods and Protocols / [ed] Vulfson, E. N.; Halling, P. J.; Holland, H. L., Totowa: Humana Press , 2001, p. 307-317Chapter in book (Refereed)
  • 13.
    Berglund, Per
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Holmquist, Mats Torsten
    KTH, Superseded Departments (pre-2005), Biochemistry and Biotechnology.
    Hult, Karl
    KTH, Superseded Departments (pre-2005), Biochemistry and Biotechnology.
    Reversed enantiopreference of Candida rugosa lipase supports different modes of binding enantiomers of a chiral acyl donor1998In: Journal of Molecular Catalysis - B Enzymatic, ISSN 1381-1177, Vol. 5, no 1-4, p. 283-287Article in journal (Refereed)
    Abstract [en]

    Molecular modelling identifies two different productive modes of binding the enantiomers of a 2-methyldecanoic acid ester to the active site of Candida rugosa lipase (CRL). The fast reacting S-enantiomer occupies the previously identified acyl-binding tunnel of the enzyme, whereas the R- enantiomer leaves the tunnel empty. The modelling suggested that if both enantiomers were forced to bind to the active site leaving the tunnel empty, the enzyme would reverse its enantiopreference to become R-enantioselective. To test this hypothesis, we designed a structural analogue to 2- methyldecanoic acid, 2-methyl-6-(2-thienyl)hexanoic acid, which was expected to be too bulky to fit its acyl moiety into the acyl-binding tunnel. The CRL- catalysed hydrolysis of the ethyl ester of this substrate resulted in the preferential conversion of the R-enantiomer as predicted by molecular modelling. This represents the first kinetic evidence supporting the existence of two different modes of binding the enantiomers of a 2- methyldecanoic acid ester to the active site of CRL. We have shown that a rational 3D based approach in combination with substrate engineering can be used to predict and control the stereochemical outcome of a lipase catalysed reaction.

  • 14.
    Berglund, Per
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Biocatalytic synthesis of enantiopure compounds using lipases: Chapter 212000In: Stereoselective Biocatalysis / [ed] Patel, R. N., New York: Marcel Dekker, 2000, p. 633-657Chapter in book (Refereed)
  • 15.
    Berglund, Per
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Svedendahl, Maria
    KTH, School of Biotechnology (BIO), Biochemistry.
    Engelmark Cassimjee, Karim
    KTH, School of Biotechnology (BIO), Biochemistry.
    Branneby, Cecilia
    Cambrex Karlskoga AB.
    Abedi, Vahak
    AstraZeneca.
    Wells, Andrew
    AstraZeneca.
    Federsel, Hans-Jürgen
    AstraZeneca.
    Omega-Transaminases Redesigned for Chiral Amine Synthesis2011In: BIT Life Sciences’ 2nd Symposium on Enzymes & Biocatalysis, Dalian, China: BIT Life Sciences , 2011Conference paper (Refereed)
  • 16.
    Berglund, Per
    et al.
    Mid Sweden University.
    Vörde, Carin
    Hogberg, Hans-Erik
    Esterification of 2-methylalkanoic acids Catalysed by Lipase from Candida rugosa: Enantioselectivity as a Function of water Activity and Alcohol Chain Length1994In: Biocatalysis and Biotransformation, ISSN 1024-2422, E-ISSN 1029-2446, Vol. 9, no 1-4, p. 123-130Article in journal (Refereed)
  • 17.
    Bi, Ran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lignocellulose Degradation by Soil Micro-organisms2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lignocellulosic biomass is a sustainable resource with abundant reserves. Compared to petroleum ‐ based products, the biomass ‐ derived polymers and chemicals give better environmental profiles. A lot of research interest is focused on understanding the lignocellulose structures.

    Lignin, among the three major wood components, represents most difficulty for microbial degradation because of its complex structure and because cross ‐ linking to hemicellulose makes wood such a compact structure. Nevertheless, wood is naturally degraded by wood ‐ degrading micro ‐ organisms and modified and partly degraded residual of lignin goes into soil. Therefore soil serves as a good environment in which to search for special lignin ‐ degraders. In this thesis, different types of lignin have been used as sole carbon sources to screen for lignin ‐ degrading soil micro ‐ organisms. Eleven aerobic and three anaerobic microbe strains have been isolated and identified as able to grow on lignin. The lignin degradation patterns of selected strains have been studied and these partly include an endwise cleavage of  β‐ O ‐ 4 bonds in lignin and is more complex than simple hydrolytic degradation.

    As lignin exists in wood covalently bonded to hemicellulose, one isolated microbe strain, Phoma herbarum, has also been studied with regards to its ability to degrade covalent lignin polysaccharide networks (LCC). The results show that its culture filtrate can attack lignin ‐ polysaccharide networks in a manner different from that of the commercial enzyme product, Gammanase, possibly by selective cleavage of phenyl glucoside bonds. The effects on LCC of Phoma herbarum also enhance polymer extractability. Hot ‐ water extraction of a culture filtrate of Phoma herbarum ‐ treated fiberized spruce wood material gave an amount of extracted galactoglucomannan more than that given by the Gammanase ‐ treated material and non ‐ enzyme ‐ treated material.

    Over millions of years of natural evolution, micro ‐ organisms on the one hand develop so that they can degrade all wood components to get energy for growth, while plants on the other hand also continuously develop to defend from microbial attack. Compared with lignin and cellulose, hemicelluloses as major components of plant cell walls, are much more easily degraded, but hemicelluloses differ from cellulose in that they are acetylated to different extents. The biological functions of acetylation are not completely understood, but it is suggested is that one function is to decrease the microbial degradability of cell walls. By cultivation of soil micro ‐ organisms using mannans acetylated to deffernent degrees as sole carbon source on agar plates, we were able to see significant trends where the resistance towards microbial degradation of glucomannan and galactomannan increased with increasing degree of acetylation. Possible mechanisms and the technological significance of this are discussed. Tailoring the degree of acetylation of polysaccharide materials might slow down the biodegradation, making it possible to design a material with a degradation rate suited to its application.

    Download full text (pdf)
    Thesis
  • 18. Billig, S.
    et al.
    Agrawal, P.B.
    Birkemeyer, C.
    Nierstrasz, Vincent
    University of Borås, Swedish School of Textiles.
    Warmoeskerken, M.M.C.G.
    Zimmerman, W.
    Biodegradation of diverse PET materials by polyester hydrolases from Thermobifida fusca and Fusarium solani2014Conference paper (Refereed)
  • 19.
    Biswas, Tuser
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Yu, Junchun
    University of Borås, Faculty of Textiles, Engineering and Business.
    Nierstrasz, Vincent
    University of Borås, Faculty of Textiles, Engineering and Business.
    Digital inkjet printing of antimicrobial lysozyme on pretreated polyester fabric2022Conference paper (Refereed)
    Abstract [en]

    Lysozyme was inkjet printed on two different polyester fabrics considering several challenges of printing enzymes on synthetic fabric surfaces. Wettability of both the fabrics were improved by alkaline pre-treatment resulting reduction in water contact angle to 60±2 from 95°±3 and to 80°±2 from 115°±2 for thinner and coarser fabric respectively. Activity of lysozyme in the prepared ink was 9240±34 units/ml and reduced to 5946±23 units/ml as of collected after jetting process (before printing on fabric). The formulated ink was effectively inkjet printed on alkali treated polyester fabric for antimicrobial applications. Retention of higher activity of the printed fabric requires further studies on enzyme-fibre binding mechanisms and understanding protein orientation on fabric surface after printing

    Download full text (pdf)
    fulltext
  • 20.
    Biswas, Tuser
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Yu, Junchun
    University of Borås, Faculty of Textiles, Engineering and Business.
    Nierstrasz, Vincent
    University of Borås, Faculty of Textiles, Engineering and Business.
    Enzyme immobilization on textiles by inkjet printing for advanced applications2019Conference paper (Refereed)
    Abstract [en]

    Immobilization of enzymes on textiles can impart a range of advanced applications e.g. anti-microbial, controlled release, drug delivery and bio-sensing (Wehrschütz-Sigl et al., 2010). Such applications enable minimal consumption, recovery, and reusability of these valuable bio-materials compared to their conventional textile applications in surface cleaning and finishing (Araujo et al., 2008). Methods used for immobilization can play important roles to ensure precise, flexible and contamination free application. Compared to many of the conventional methods of textile immobilization such as coating and screen-printing, digital inkjet technology offers many benefits for such advanced applications (Kan and Yuen, 2012). Among various inkjet technologies, drop-on-demand piezoelectric printing is a promising resource-efficient technology for enzyme immobilization. 

     

    The enzymes should retain high activity after the immobilization process. Various factors involved during inkjet printing (Saunders and Derby, 2014) and fabric characteristics (Mohamed et al., 2008) can influence this enzymatic activity. Factors concerning the inkjet procedure include rheology and ionic nature of ink along with the shear force and waveform generated inside a piezoelectric printhead (Magdassi, 2010). Factors dependent upon fabric characteristics include surface structure, pore size distribution, and binding mechanism (Nierstrasz and Warmoeskerken, 2003). In this work, we have studied the effects of inkjet procedures on enzymatic activity. Lysozyme being a stable and well-studied enzyme was chosen for our experiments. A Xennia Carnelian printer with a Dimatix QS10 industrial printhead was used for inkjetting. Lytic activity of lysozyme was studied by a UV-Vis spectrophotometer against decrease of Micrococcus lysodeikticus cell concentration at 450 nm. Results showed ca. 10-15% activity reduction of the jetted lysozyme ink. As all the ink and printer parameters were optimized, the probable reason for such reduction could be the effect of shear forces inside the printhead on three-dimensional conformation of lysozyme. In conclusion, our formulated lysozyme ink showed potential for printing textiles with probable activity reduction that require further investigation. 

  • 21.
    Biswas, Tuser
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Yu, Junchun
    University of Borås, Faculty of Textiles, Engineering and Business.
    Nierstrasz, Vincent
    University of Borås, Faculty of Textiles, Engineering and Business.
    Inkjet printing of enzymes on synthetic fabrics2022Conference paper (Refereed)
    Abstract [en]

    Enzymes can be immobilized on textiles to impart anti-microbial properties in a more environment-friendly manner compared to conventional biocide-based solutions. Such application requires ensuring precise, flexible and contamination-free immobilization methods that can be offered by digital printing compared to coating or screen-printing techniques. Drop-on-demand inkjet printing is a resource-efficient technology that can ensure these requirements. The use of polyester and polyamide-based fabrics is rising for applications ranging from apparel and home furnishing to hygiene and medical textiles. These fibers offer superior chemical, physical, and mechanical properties due to their inert nature but challenge the printing process due to hydrophobicity and lack of functional groups. Lysozyme and tyrosinase are two enzymes showing great potential for grafting on synthetic fabrics paving the way to use them for inkjet printing as well.

    Challenges for inkjet printing of enzymes on synthetic fabric surfaces come in multiple forms i.e. ink recipe formation, printer mechanics and fabric surface characteristics. The ink must maintain a suitable viscosity and surface tension for effective drop ejection and a feasible ionic nature for enzyme activity. Then, the enzyme must be able to sustain the temperature and shear stress generated inside an inkjet printhead. Finally, influential fabric characteristics include surface structure, pore size distribution, evaporation rate and binding mechanism. By considering these parameters, lysozyme and tyrosinase were successfully printed on variously modified synthetic fabrics using a combination of sustainable technologies.

  • 22.
    Biundo, Antonino
    et al.
    Univ Nat Resources & Life Sci, Vienna, Austria..
    Ribitsch, Doris
    Austrian Ctr Ind Biotechnol, Graz, Austria..
    Syrén, Per-Olof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. Vienna, Austria..
    Guebitz, Georg M.
    Univ Nat Resources & Life Sci, Vienna, Austria..
    Increasing amide acceptance on a polyester-hydrolyzing enzyme2016In: New Biotechnology, ISSN 1871-6784, E-ISSN 1876-4347, Vol. 33, p. S105-S105Article in journal (Other academic)
  • 23.
    Biundo, Antonino
    et al.
    University of Bari, Department of Biosciences, Biotechnology and Biopharmaceutics, via Orabona, 4, Bari, 70125, Italy, via Orabona, 4; REWOW srl, Via Ciasca 9, Bari, 70124, Italy, Via Ciasca 9.
    Saénz Méndez, Patricia
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. Karlstads Universitet, Faculty of Health, Science and Technology, Universitetsgatan 2, 65188 Karlstad, Sweden.
    Görbe, Tamas
    Menten AI, 2225 E Bayshore Road, Suite 200, Palo Alto, CA, 94303, USA.
    Enzyme Modification2021In: Biocatalysis for Practitioners: Techniques, Reactions and Applications, Wiley , 2021, p. 33-62Chapter in book (Other academic)
    Abstract [en]

    The chapter on protein engineering has introduced and discussed an overview of the available methods for the modification of enzymes. Starting with the classical directed evolution (DE) technique, which has been applied extensively throughout several different biocatalytic processes, the reader moves toward the semi-rational, rational, and de novo design of enzymes. Meanwhile, DE is clearly the current industry-leading technology; depending on the understanding of the particular enzymatic system, and on the available structural information, other techniques such as rational design are also becoming fast and efficient solutions for the development of new catalysts. This success would not be possible without the constant improvements of the computational techniques and the newly developed modeling systems for enzyme engineering.

  • 24.
    Blissing, Annica
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Thiopurine S-methyltransferase - characterization of variants and ligand binding2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thiopurine S-methyltransferase (TPMT) belongs to the Class I S-adenosylmethionine-dependent methyltransferase (SAM-MT) super family of structurally related proteins. Common to the members of this large protein family is the catalysis of methylation reactions using S-adenosylmethionine (SAM) as a methyl group donor, although SAM-MTs act on a wide range of different substrates and carry out numerous biologically important functions. While the natural function of TPMT is unknown, this enzyme is involved in the metabolism of thiopurines, a class of pharmaceutical substances administered in treatment of immune-related disorders. Specifically, methylation by TPMT inactivates thiopurines and their metabolic intermediates, which reduces the efficacy of clinical treatment and increases the risk of adverse side effects. To further complicate matters, TPMT is a polymorphic enzyme with over 40 naturally occurring variants known to date, most of which exhibit lowered methylation activity towards thiopurines. Consequently, there are individual variations in TPMTmediated thiopurine inactivation, and the administered dose has to be adjusted prior to clinical treatment to avoid harmful side effects.

    Although the clinical relevance of TPMT is well established, few studies have investigated the molecular causes of the reduced methylation activity of variant proteins. In this thesis, the results of biophysical characterization of two variant proteins, TPMT*6 (Y180F) and TPMT*8 (R215H), are presented. While the properties of TPMT*8 were indistinguishable from those of the wild-type protein, TPMT*6 was found to be somewhat destabilized. Interestingly, the TPMT*6 amino acid substitution did not affect the functionality or folding pattern of the variant protein. Therefore, the decreased in vivo functionality reported for TPMT*6 is probably caused by increased proteolytic degradation in response to the reduced stability of this protein variant, rather than loss of function.

    Also presented herein are novel methodological approaches for studies of TPMT and its variants. Firstly, the advantages of using 8-anilinonaphthalene-1-sulfonic acid (ANS) to probe TPMT tertiary structure and active site integrity are presented. ANS binds exclusively to the native state of TPMT with high affinity (KD ~ 0.2 μm) and a 1:1 ratio. The stability of TPMT was dramatically increased by binding of ANS, which was shown to co-localize with the structurally similar adenine moiety of the cofactor SAM. Secondly, an enzyme activity assay based on isothermal titration calorimetry (ITC) is presented. Using this approach, the kinetics of 6-MP and 6-TG methylation by TPMT has been characterized.

    Download full text (pdf)
    Thiopurine S-methyltransferase characterization of variants and ligand binding
    Download (pdf)
    omslag
    Download (jpg)
    presentationsbild
  • 25.
    Blomqvist, J.
    et al.
    Department of Microbiology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    South, E.
    Department of Microbiology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Tiukova, L.
    Department of Microbiology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Momeni, M. H.
    Department of Molecular Biology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Hansson, H.
    Department of Molecular Biology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Ståhlberg, J.
    Department of Molecular Biology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Horn, S. J.
    Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Ås, Norway.
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden.
    Passoth, V.
    Department of Microbiology, Uppsala Biocenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Fermentation of lignocellulosic hydrolysate by the alternative industrial ethanol yeast Dekkera bruxellensis2011In: Letters in Applied Microbiology, ISSN 0266-8254, E-ISSN 1472-765X, Vol. 53, no 1, p. 73-78Article in journal (Refereed)
    Abstract [en]

    Aim: Testing the ability of the alternative ethanol production yeast Dekkera bruxellensis to produce ethanol from lignocellulose hydrolysate and comparing it to Saccharomyces cerevisiae.

    Methods and Results: Industrial isolates of D. bruxellensis and S. cerevisiae were cultivated in small-scale batch fermentations of enzymatically hydrolysed steam exploded aspen sawdust. Different dilutions of hydrolysate were tested. None of the yeasts grew in undiluted or 1 : 2 diluted hydrolysate [final glucose concentration always adjusted to 40 g l(-1) (0.22 mol l(-1))]. This was most likely due to the presence of inhibitors such as acetate or furfural. In 1 : 5 hydrolysate, S. cerevisiae grew, but not D. bruxellensis, and in 1 : 10 hydrolysate, both yeasts grew. An external vitamin source (e.g. yeast extract) was essential for growth of D. bruxellensis in this lignocellulosic hydrolysate and strongly stimulated S. cerevisiae growth and ethanol production. Ethanol yields of 0 42 +/- 0 01 g ethanol (g glucose)(-1) were observed for both yeasts in 1 : 10 hydrolysate. In small-scale continuous cultures with cell recirculation, with a gradual increase in the hydrolysate concentration, D. bruxellensis was able to grow in 1 : 5 hydrolysate. In bioreactor experiments with cell recirculation, hydrolysate contents were increased up to 1 : 2 hydrolysate, without significant losses in ethanol yields for both yeasts and only slight differences in viable cell counts, indicating an ability of both yeasts to adapt to toxic compounds in the hydrolysate.

    Conclusions: Dekkera bruxellensis and S. cerevisiae have a similar potential to ferment lignocellulose hydrolysate to ethanol and to adapt to fermentation inhibitors in the hydrolysate.

    Significance and Impact of the study: This is the first study investigating the potential of D. bruxellensis to ferment lignocellulosic hydrolysate. Its high competitiveness in industrial fermentations makes D. bruxellensis an interesting alternative for ethanol production from those substrates.

  • 26.
    Branneby, Cecilia
    et al.
    Cambrex Karlskoga AB.
    Svedendahl, Maria
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Lipase-Catalyzed Aldol and Michael-Type Reactions2005In: Book of abstracts, 2005Conference paper (Refereed)
  • 27.
    Branneby, Cecilia
    et al.
    Cambrex Karlskoga AB.
    Svedendahl, Maria
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Lipase-Catalyzed Aldol and Michael-Type Reactions2006Conference paper (Refereed)
  • 28.
    Broberg, Anders
    et al.
    Department of Chemistry, Swedish University of Agricultural Sciences, Sweden.
    Jacobsson, Karin
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Ström, Katrin
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Schnürer, Johan
    Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Metabolite profiles of lactic acid bacteria in grass silage2007In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 73, no 17, p. 5547-5552Article in journal (Refereed)
    Abstract [en]

    The metabolite production of lactic acid bacteria JAB) on silage was investigated. The aim was to compare the production of antifungal metabolites in silage with the production in liquid cultures previously studied in our laboratory. The following metabolites were found to be present at elevated concentrations in silos inoculated with LAB strains: 3-hydroxydecanoic acid, 2-hydroxy-4-methylpentanoic acid, benzoic acid, catechol, hydrocinnamic acid, salicylic acid, 3-phenyllactic acid, 4-hydroxybenzoic acid, (trans, trans)-3,4-dihydroxycyclohexane-1-carboxylic acid, p-hydrocoumaric acid, vanillic acid, azelaic acid, hydroferulic acid, p-coumaric acid, hydrocaffeic acid, ferulic acid, and caffeic acid. Among these metabolites, the antifungal compounds 3-phenyllactic acid and 3-hydroxydecanoic acid were previously isolated in our laboratory from liquid cultures of the same LAB strains by bioassay-guided fractionation. It was concluded that other metabolites, e.g., p-hydrocoumaric acid, hydroferulic acid, and p-coumaric acid, were released from the grass by the added LAB strains. The antifungal activities of the identified metabolites in 100 mM lactic acid were investigated. The MICs against Pichia anomala, Penicillium roqueforti, and Aspergillus fumigatus were determined, and 3-hydroxydecanoic acid showed the lowest MIC (0.1 mg ml(-1) for two of the three test organisms).

  • 29.
    Cao, Hongwei
    et al.
    Univ Shanghai Sci & Technol, Sch Hlth Sci & Engn, Shanghai, Peoples R China.;Natl Grain Ind Urban Grain & Oil Secur Technol Inn, Shanghai, Peoples R China..
    Wang, Xiaoxue
    Univ Shanghai Sci & Technol, Sch Hlth Sci & Engn, Shanghai, Peoples R China..
    Liu, Jing
    Shanghai Maritime Univ, Coll Informat Engn, Shanghai, Peoples R China..
    Sun, Zhu
    Inner Mongolia Yangufang Whole Grain Ind Dev Co Lt, Shanghai, Peoples R China..
    Yu, Zhiquan
    Inner Mongolia Yangufang Whole Grain Ind Dev Co Lt, Shanghai, Peoples R China..
    Battino, Maurizio
    Polytech Univ Marche, Dept Clin Sci, Ancona, Italy.;Jiangsu Univ, Int Joint Res Lab Intelligent Agr & Agriprod Proc, Zhenjiang, Peoples R China.;Univ Europea Atlantico, Res Grp Foods Nutr Biochem & Hlth, Santander, Spain..
    El-Seedi, Hesham
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences. Jiangsu Univ, Int Res Ctr Food Nutr & Safety, Zhenjiang, Peoples R China..
    Guan, Xiao
    Univ Shanghai Sci & Technol, Sch Hlth Sci & Engn, Shanghai, Peoples R China.;Natl Grain Ind Urban Grain & Oil Secur Technol Inn, Shanghai, Peoples R China..
    Mechanistic insights into the changes of enzyme activity in food processing under microwave irradiation2023In: Comprehensive Reviews in Food Science and Food Safety, E-ISSN 1541-4337, Vol. 22, no 3, p. 2465-2487Article, review/survey (Refereed)
    Abstract [en]

    Microwave (MW) and enzyme catalysis are two emerging processing tools in the field of food industry. Recently, MW has been widely utilized as a novel type of green and safe heating energy. However, the effect of MW irradiation on enzyme activity is not described clearly. The intrinsic mechanisms behind enzyme activation and inactivation remain obscure. To apply better MW to the field of enzyme catalysis, it is essential to gain insights into the mechanism of MW action on enzyme activity. This review summarizes the changes in various enzyme activity during food processing, especially under MW irradiation. The intrinsic mechanism of thermal and nonthermal effects of MW irradiation was analyzed from the perspective of enzyme reaction kinetics and spatial structure. MW irradiation temperature is a vital parameter affecting the catalytic activity of enzymes. Activation of the enzyme activity is achieved even at high MW power when the enzyme is operating at its optimum temperature. However, when the temperature exceeds the optimum temperature, the enzyme activity is inhibited. In addition to MW dielectric heating effect, nonthermal MW effects also alter the microenvironment of reactive system. Taken together, enzyme activity is influenced by both thermal and nonthermal MW effects.

  • 30.
    Carvalho, Alexandra T P
    et al.
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Computational and Systems Biology.
    Barrozo, Alexandre
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Computational and Systems Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Doron, Dvir
    Kilshtain, Alexandra Vardi
    Major, Dan Thomas
    Kamerlin, Lynn Shina Caroline
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Computational and Systems Biology.
    Challenges in computational studies of enzyme structure, function and dynamics2014In: Journal of Molecular Graphics and Modelling, ISSN 1093-3263, E-ISSN 1873-4243, Vol. 54, p. 62-79Article, review/survey (Refereed)
    Abstract [en]

    In this review we give an overview of the field of Computational enzymology. We start by describing the birth of the field, with emphasis on the work of the 2013 chemistry Nobel Laureates. We then present key features of the state-of-the-art in the field, showing what theory, accompanied by experiments, has taught us so far about enzymes. We also briefly describe computational methods, such as quantum mechanics-molecular mechanics approaches, reaction coordinate treatment, and free energy simulation approaches. We finalize by discussing open questions and challenges.

    Download full text (pdf)
    fulltext
  • 31.
    Cavka, Adnan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Biorefining of lignocellulose: Detoxification of inhibitory hydrolysates and potential utilization of residual streams for production of enzymes2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lignocellulosic biomass is a renewable resource that can be utilized for the production of biofuels, chemicals, and bio-based materials. Biochemical conversion of lignocellulose to advanced biofuels, such as cellulosic ethanol, is generally performed through microbial fermentation of sugars generated by thermochemical pretreatment of the biomass followed by an enzymatic hydrolysis of the cellulose. The aims of the research presented in this thesis were to address problems associated with pretreatment by-products that inhibit microbial and enzymatic biocatalysts, and to investigate the potential of utilizing residual streams from pulp mills and biorefineries to produce hydrolytic enzymes.

    A novel method to detoxify lignocellulosic hydrolysates to improve the fermentability was investigated in experiments with the yeast Saccharomyces cerevisiae. The method is based on treatment of lignocellulosic slurries and hydrolysates with reducing agents, such as sodium dithionite and sodium sulfite. The effects of treatment with sodium borohydride were also investigated. Treatment of a hydrolysate of Norway spruce by addition of 10 mM dithionite resulted in an increase of the balanced ethanol yield from 0.03 to 0.35 g/g. Similarly, the balanced ethanol yield of a hydrolysate of sugarcane bagasse increased from 0.06 to 0.28 g/g after treatment with 10 mM dithionite. In another study with a hydrolysate of Norway spruce, addition of 34 mM borohydride increased the balanced ethanol yield from 0.02 to 0.30 g/g, while the ethanol productivity increased from 0.05 to 0.57 g/(L×h). While treatment with sulfur oxyanions had a positive effect on microbial fermentation and enzymatic hydrolysis, treatment with borohydride resulted in an improvement only for the microbial fermentation. The chemical effects of treatments of hydrolysates with sodium dithionite, sodium sulfite, and sodium borohydride were investigated using liquid chromatography-mass spectrometry (LC-MS). Treatments with dithionite and sulfite were found to rapidly sulfonate inhibitors already at room temperature and at a pH that is compatible with enzymatic hydrolysis and microbial fermentation. Treatment with borohydride reduced inhibitory compounds, but the products were less hydrophilic than the products obtained in the reactions with the sulfur oxyanions.

    The potential of on-site enzyme production using low-value residual streams, such as stillage, was investigated utilizing recombinant Aspergillus niger producing xylanase and cellulase. A xylanase activity of 8,400 nkat/ml and a cellulase activity of 2,700 nkat/ml were reached using stillages from processes based on waste fiber sludge. The fungus consumed a large part of the xylose, the acetic acid, and the oligosaccharides that were left in the stillages after fermentation with S. cerevisiae. In another study, the capability of two filamentous fungi (A. niger and Trichoderma reesei) and three yeasts (S. cerevisiae, Pichia pastoris, and Yarrowia lipolytica) to grow on inhibitory lignocellulosic media were compared. The results indicate that the two filamentous fungi had the best capability to utilize different nutrients in the media, while the S. cerevisiae strain exhibited the best tolerance against the inhibitors. Utilization of different nutrients would be especially important in enzyme production using residual streams, while tolerance against inhibitors is desirable in a consolidated bio-process in which the fermenting microorganism also contributes by producing enzymes.

    Download full text (pdf)
    Biorefining of lignocellulose
  • 32.
    Cavka, Adnan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Alriksson, Björn
    Processum Biorefinery Initiative AB, 891 22 Örnsköldsvik, Sweden.
    Rose, Shaunita H.
    Department of Microbiology, Stellenbosch University, Stellenbosch, 7602, South Africa.
    van Zyl, Willem H.
    Department of Microbiology, Stellenbosch University, Stellenbosch, 7602, South Africa.
    Jönsson, Leif J.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Production of cellulosic ethanol and enzyme from waste fiber sludge using SSF, recycling of hydrolytic enzymes and yeast, and recombinant cellulase-producing Aspergillus niger2014In: Journal of Industrial Microbiology & Biotechnology, ISSN 1367-5435, E-ISSN 1476-5535, Vol. 41, no 8, p. 1191-1200Article in journal (Refereed)
    Abstract [en]

    Bioethanol and enzymes were produced from fiber sludges through sequential microbial cultivations. After a first simultaneous saccharification and fermentation (SSF) with yeast, the bioethanol concentrations of sulfate and sulfite fiber sludges were 45.6 and 64.7 g/L, respectively. The second SSF, which included fresh fiber sludges and recycled yeast and enzymes from the first SSF, resulted in ethanol concentrations of 38.3 g/L for sulfate fiber sludge and 24.4 g/L for sulfite fiber sludge. Aspergillus niger carrying the endoglucanase-encoding Cel7B gene of Trichoderma reesei was grown in the spent fiber sludge hydrolysates. The cellulase activities obtained with spent hydrolysates of sulfate and sulfite fiber sludges were 2,700 and 2,900 nkat/mL, respectively. The high cellulase activities produced by using stillage and the significant ethanol concentrations produced in the second SSF suggest that onsite enzyme production and recycling of enzyme are realistic concepts that warrant further attention.

  • 33.
    Cavka, Adnan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jönsson, Leif J.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Comparison of the growth of filamentous fungi and yeasts in lignocellulose-derived media2014In: Biocatalysis and Agricultural Biotechnology, E-ISSN 1878-8181, Vol. 3, no 4, p. 197-204Article in journal (Refereed)
    Abstract [en]

    Five microorganisms of potential interest for on-site enzyme production in lignocellulosic biorefineries were evaluated with regard to inhibitor tolerance and nutrient utilization. Prehydrolysate and hydrolysate of Norway spruce were used in concentrations of 25%, 50%, 75% and 100% and compared to reference media without fermentation inhibitors. Monosaccharide sugars, oligosaccharides, and small aliphatic acids were monitored to investigate nutrient utilization in the lignocellulosic media. The microorganisms studied were the filamentous fungi Aspergillus niger and Trichoderma reesei and the three yeasts Pichia pastoris, Saccharomyces cerevisiae, and Yarrowia lipolytica. All five fungi had the ability to grow in media with 25% prehydrolysate or 25% hydrolysate. The S. cerevisiae strain had the highest inhibitor tolerance of the microorganisms studied and grew in media with 50% prehydrolysate or 75% hydrolysate. In medium with 25% prehydrolysate A. niger and Y. lipolytica gave high biomass yields of 0.46 and 0.32 g/g on initial carbon source, which corresponded to 0.46 and 0.43 g/g on consumed carbon source, respectively. The ethanol yield on consumed carbon source in 50% hydrolysate was 0.29 g/g for P. pastoris and 0.33. g/g for S. cerevisiae. The capability of A. niger to utilize a broad range of nutrients appears especially useful for enzyme production using residual streams. The high tolerance against inhibitors exhibited by S. cerevisiae could be particularly useful in a consolidated bio-process where the fermenting microorganism contributes also by producing enzymes.

    Download full text (pdf)
    fulltext
  • 34.
    Chandrakumaran, Sajitha
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology.
    Investigation of an enzymatic cascade for the production of 5- hydroxymethylfurfurylamine2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Biocatalysis is a promising alternative to chemical synthesis routes for high value chemicals which considers the sustainability and environmental aspect. In this study the feasibility of utilizing an enzymatic cascade for the production of 5-hydroxymethylfurfurylamine (HMFA) was explored. HMFA is a compound with diverse applications in industries such as agriculture and pharmaceuticals. The cascade consists of two main reactions, the first of which involves the decarboxylation of lysine using a lysine decarboxylase to produce cadaverine. The cadaverine produced will then be utilized as an amine donor in the second reaction, which involves the use of a transaminase derived from Silicibacter pomeroyi (SpTA) together with 5-hydroxymethylfurfural (HMF). This cascade considers the principals of green chemistry such as milder reaction conditions and less waste, hence aiming to reduce the environmental impact. Although there were challenges preventing the completion of the enzymatic cascade, valuable insights were gained. The contribution of this study sheds light on the intricate reaction mechanisms and some of the key difficulties with enzyme immobilisation. While the intended cascade was not finalized, the lessons learned will provide for new perspectives and potential future advancements in biocatalysis. 

    Download full text (pdf)
    fulltext
  • 35.
    Chawachart, Niwat
    et al.
    Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand.
    Anbarasan, Sasikala
    Department of Biotechnology and Chemical Technology, School of Chemical Technology, Aalto University, P.O. Box 16100, 00076, Aalto, Finland.
    Turunen, Samuel
    Department of Biotechnology and Chemical Technology, School of Chemical Technology, Aalto University, P.O. Box 16100, 00076, Aalto, Finland.
    Li, He
    Department of Biotechnology and Chemical Technology, School of Chemical Technology, Aalto University, P.O. Box 16100, Aalto, 00076, Finland.
    Khanongnuch, Chartchai
    Department of Biotechnology, Faculty of Agro-Industry, Chiang Mai University, Chiang Mai, 50200, Thailand.
    Hummel, Michael
    Department of Forest Products Technology, School of Chemical Technology, Aalto University, P.O. Box 16300, 00076, Aalto, Finland.
    Sixta, Herbert
    Department of Forest Products Technology, School of Chemical Technology, Aalto University, P.O. Box 16300, 00076, Aalto, Finland.
    Granström, Tom
    Department of Biotechnology and Chemical Technology, School of Chemical Technology, Aalto University, P.O. Box 16100, 00076, Aalto, Finland.
    Lumyong, Saisamorn
    Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand.
    Turunen, Ossi
    Department of Biotechnology and Chemical Technology, School of Chemical Technology, Aalto University, P.O. Box 16100, 00076, Aalto, Finland.
    Thermal behaviour and tolerance to ionic liquid [emim] OAc in GH10 xylanase from Thermoascus aurantiacus SL16W2014In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 18, no 6, p. 1023-1034Article in journal (Refereed)
    Abstract [en]

    GH10 xylanase from Thermoascus aurantiacus strain SL16W (TasXyn10A) showed high stability and activity up to 70–75 C. The enzyme’s half-lives were 101 h, 65 h, 63 min and 6 min at 60, 70, 75 and 80 C, respectively. The melting point (Tm), as measured by DSC, was 78.5 C, which is in line with a strong activity decrease at 75–80 C. The biomass-dissolving ionic liquid 1-ethyl-3-methylimidazolium acetate ([emim]OAc) in 30 % concentration had a small effect on the stability of TasXyn10A; Tm decreased by only 5 C. It was also observed that [emim]OAc inhibited much less GH10 xylanase (TasXyn10A) than the studied GH11 xylanases. The Km of TasXyn10A increased 3.5-fold in 15 % [emim]OAc with xylan as the substrate, whereas the approximate level of Vmax was not altered. The inhibition of enzyme activity by [emim]OAc was lesser at higher substrate concentrations. Therefore, high solid concentrations in industrial conditions may mitigate the inhibition of enzyme activity by ionic liquids. Molecular docking experiments indicated that the [emim] cation has major binding sites near the catalytic residues but in lower amounts in GH10 than in GH11 xylanases. Therefore, [emim] cation likely competes with the substrate when binding to the active site. The docking results indicated why the effect is lower in GH10.

  • 36.
    Chen, Shan
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Land, Henrik
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Svedendahl Humble, Maria
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Stabilization of an amine transaminase for biocatalysis2016In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 124, p. 20-28Article in journal (Refereed)
    Abstract [en]

    The amine transaminase from Chromobacterium violaceum (Cv-ATA) is a well-known enzyme to achievechiral amines of high enantiomeric excess in laboratory scales. However, the low operational stabilityof Cv-ATA limits the enzyme applicability on larger scales. In order to improve the operational stabilityof Cv-ATA, and thereby extending its applicability, factors (additives, co-solvents, organic solvents anddifferent temperatures) targeting enzyme stability and activity were explored in order to find out how tostore and apply the enzyme. The present investigation shows that the melting point of Cv-ATA is improvedby adding sucrose or glycerol, separately. Further, by storing the enzyme at higher concentrations and inco-solvents, such as; 50% glycerol, 20% methanol or 10% DMSO, the active dimeric structure of Cv-ATAis retained. Enzyme stored in 50% glycerol at −20◦C was e.g., still fully active after 6 months. Finally,the enzyme performance was improved 5-fold by a co-lyophilization with surfactants prior to usage inisooctane.

  • 37. Christou, Nina Eleni
    et al.
    Lane, Thomas J.
    et al.,
    Time-resolved crystallography captures light-driven DNA repair2023In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 382, no 6674, p. 1015-1020Article in journal (Refereed)
    Abstract [en]

    Photolyase is an enzyme that uses light to catalyze DNA repair. To capture the reaction intermediates involved in the enzyme's catalytic cycle, we conducted a time-resolved crystallography experiment. We found that photolyase traps the excited state of the active cofactor, flavin adenine dinucleotide (FAD), in a highly bent geometry. This excited state performs electron transfer to damaged DNA, inducing repair. We show that the repair reaction, which involves the lysis of two covalent bonds, occurs through a single-bond intermediate. The transformation of the substrate into product crowds the active site and disrupts hydrogen bonds with the enzyme, resulting in stepwise product release, with the 3' thymine ejected first, followed by the 5' base.

  • 38. Dan, Meiling
    et al.
    Zheng, Yuting
    Zhao, Guohua
    Hsieh, Yves S. Y.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Wang, Damao
    Current insights of factors interfering the stability of lytic polysaccharide monooxygenases2023In: Biotechnology Advances, ISSN 0734-9750, E-ISSN 1873-1899, Vol. 67, p. 108216-108216, article id 108216Article in journal (Refereed)
    Abstract [en]

    Cellulose and chitin are two of the most abundant biopolymers in nature, but they cannot be effectively utilized in industry due to their recalcitrance. This limitation was overcome by the advent of lytic polysaccharide monooxygenases (LPMOs), which promote the disruption of biopolymers through oxidative mechanism and provide a breakthrough in the action of hydrolytic enzymes. In the application of LPMOs to biomass degradation, the key to consistent and effective functioning lies in their stability. The efficient transformation of biomass resources using LPMOs depends on factors that interfere with their stability. This review discussed three aspects that affect LPMO stability: general external factors, structural factors, and factors in the enzyme-substrate reaction. It explains how these factors impact LPMO stability, discusses the resulting effects, and finally presents relevant measures and considerations, including potential resolutions. The review also provides suggestions for the application of LPMOs in polysaccharide degradation. 

  • 39.
    Digaitis, Ramunas
    et al.
    Malmö University, Biofilms Research Center for Biointerfaces. Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, Frederiksberg C, Denmark.
    Thybring, Emil Engelund
    Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, Frederiksberg C, Denmark.
    Thygesen, Lisbeth Garbrecht
    Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, Frederiksberg C, Denmark.
    Investigating the role of mechanics in lignocellulosic biomass degradation during hydrolysis: Part II2021In: Biotechnology progress (Print), ISSN 8756-7938, E-ISSN 1520-6033, Vol. 37, no 1, article id e3083Article in journal (Refereed)
    Abstract [en]

    Lignocellulose breakdown in biorefineries is facilitated by enzymes and physical forces. Enzymes degrade and solubilize accessible lignocellulosic polymers, primarily on fiber surfaces, and make fibers physically weaker. Meanwhile physical forces acting during mechanical agitation induce tearing and cause rupture and attrition of the fibers, leading to liquefaction, that is, a less viscous hydrolysate that can be further processed in industrial settings. This study aims at understanding how mechanical agitation during enzymatic saccharification can be used to promote fiber attrition. The effects of reaction conditions, such as substrate and enzyme concentration on fiber attrition rate and hydrolysis yield were investigated. To gain insight into the fiber attrition mechanism, enzymatic hydrolysis was compared to hydrolysis by use of hydrochloric acid. Results show that fiber attrition depends on several factors concerning reactor design and operation including drum diameter, rotational speed, mixing schedule, and concentrations of fibers and enzymes. Surprisingly, different fiber attrition patterns during enzymatic and acid hydrolysis were found for similar mixing schedules. Specifically, for tumbling mixing, slow continuous mixing appears to function better than faster, intermittent mixing even for the same total number of drum revolutions. The findings indicate that reactor design and operation as well as hydrolysis conditions are key to process optimization and that detailed insights are needed to obtain fast liquefaction without sacrificing saccharification yields.

    Download full text (pdf)
    fulltext
  • 40.
    Dorst, Kevin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Engström, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Angles d'Ortoli, Thibault
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mobarak, Hani
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ebrahemi, Azad
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fagerberg, Ulf
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Whitfield, Dennis M.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    On the influence of solvent on the stereoselectivity of glycosylation reactions2024In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 535, article id 109010Article in journal (Refereed)
    Abstract [en]

    Methodology development in carbohydrate chemistry entails the stereoselective formation of C-O bonds as a key step in the synthesis of oligo- and polysaccharides. The anomeric selectivity of a glycosylation reaction is affected by a multitude of parameters, such as the nature of the donor and acceptor, activator/promotor system, temperature and solvent. The influence of different solvents on the stereoselective outcome of glycosylation reactions employing thioglucopyranosides as glycosyl donors with a non-participating protecting group at position 2 has been studied. A large change in selectivity as a function of solvent was observed and a correlation between selectivity and the Kamlet-Taft solvent parameter pi* was found. Furthermore, molecular modeling using density functional theory methodology was conducted to decipher the role of the solvent and possible reaction pathways were investigated.

  • 41.
    Eivazihollagh, Alireza
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Svanedal, Ida
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    On chelating surfactants: Molecular perspectives and application prospects2019In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 278, p. 688-705Article in journal (Refereed)
    Abstract [en]

    Chelating agents, molecules that very strongly coordinates certain metal ions, are used industrially as well as in consumer products to minimize disturbances and increase performance of reactions and applications. The widely used sequestering agents, nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) belong to this branch of readily water-soluble compounds. When these chemical structures also have hydrophobic parts, they are prone to adsorb at air-water interfaces and to self-assemble. Such bifunctional molecules can be called chelating surfactants and will have more extended utilization prospects than common chelating agents or ordinary ionic surfactants. The present review attempts to highlight the fundamental behavior of chelating surfactants in solution and at interfaces, and their very specific interactions with metal ions. Methods to recover chelating surfactants from metal chelates are also described. Moreover, utilization of chelating surfactants in applications for metal removal in environmental engineering and mineral processing, as well as for metal control in the fields of biology, chemistry and physics, is exemplified and discussed.

  • 42.
    Engelmark Cassimjee, Karim
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Affinity Tag Purification Method and Immobilization of the Promiscuous Enzyme Alanine Racemase2006Conference paper (Refereed)
  • 43.
    Engelmark Cassimjee, Karim
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Affinity Tag Purification Method of the Promiscuous Enzyme Alanine Racemase2006In: Book of abstracts, 2006Conference paper (Other academic)
  • 44.
    Engelmark Cassimjee, Karim
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Immobilization Method for the Promiscuous Enzyme Alanine Racemase2007In: BIOTRANS Oviedo 2007 / [ed] Vicente Gotor, 2007Conference paper (Refereed)
  • 45.
    Engelmark Cassimjee, Karim
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Branneby, Cecilia
    Cambrex Karlskoga AB.
    Sjöstrand, Ulf
    Cambrex Karlskoga AB.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    High Yield Transamination with Isopropyl Amine as Donor, by Employment of YADH and in situ Cofactor Regeneration2009In: Book of abstracts, 2009Conference paper (Refereed)
  • 46.
    Engelmark Cassimjee, Karim
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Branneby, Cecilia
    Cambrex Karlskoga AB.
    Sjöstrand, Ulf
    Cambrex Karlskoga AB.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    High Yield Transamination with Isopropyl Amine as Donor, by Employment of YADH and in situ Cofactor Regeneration2009Conference paper (Refereed)
  • 47.
    Engelmark Cassimjee, Karim
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Kourist, Robert
    University of Greifswald, Germany.
    Lindberg, Diana
    Uppsala university, SE.
    Wittrup Larsen, Marianne
    KTH, School of Biotechnology (BIO), Biochemistry.
    Widersten, Mikael
    Uppsala university, SE.
    Bornscheuer, Uwe T
    University of Greifswald, DE.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    A One Step Enzyme Extraction and Immobilization Method for Organic and Aqueous Solvents2008In: Biocat2008 / [ed] Ralf Grote, Garabed Antranikian, Hamburg, Germany: TuTech Innovation GmbH , 2008Conference paper (Refereed)
  • 48.
    Engelmark Cassimjee, Karim
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Kourist, Robert
    University of Greifswald, Germany.
    Lindberg, Diana
    Uppsala university, SE.
    Wittrup Larsen, Marianne
    KTH, School of Biotechnology (BIO), Biochemistry.
    Widersten, Mikael
    Uppsala university, SE.
    Bornscheuer, Uwe T
    University of Greifswald, DE.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    A One Step General Enzyme Immobilization Method for Organic and Aqueous Solvents2008In: Book of Abstracts, 2008Conference paper (Refereed)
  • 49.
    Engelmark Cassimjee, Karim
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Svedendahl, Maria
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Rational Redesign of omega-Transaminase2010In: Biocat2010, Hamburg, Germany: TuTech Verlag , 2010Conference paper (Refereed)
  • 50.
    Enugala, Thilak Reddy
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Engineered Alcohol Dehydrogenases for Stereoselective Chemical Transformations2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Enzymes are biomolecules built from amino acids and catalyze the chemical transformations in a cell. Enzymes are by nature stereoselective, biodegradable, environmentally friendly, and can perform catalysis in aqueous solutions and at ambient temperatures. Due to these advantages the use of enzymes as biocatalysts for chemical transformations has emerged as an attractive “greener” alternative to conventional chemical synthesis strategies. And, if naturally occurring enzymes cannot carry out the desired chemical transformations, the functional properties of enzymes can be modified by directed evolution or protein engineering techniques. Since enzymes are genetically encoded they can be optimized for desired traits such as substrate selectivity or improved catalytic efficiency. Considering these advantages and also keeping the synthetic and industrial application in mind, we have employed alcohol dehydrogenase-A (ADH-A) from Rhodococcus ruber DSM 44541 as a study object in engineering for new catalytic properties. ADH-A tolerates water miscible organic solvents, accepts a relatively wide range of aromatic sec-alcohols/ketones as substrates and is therefore a potentially useful biocatalyst for asymmetric synthesis of organic compounds.

     

    Presented research work in this thesis has been primarily focused on engineering of ADH-A and characterization of resulting enzyme variants. The engineering efforts have aimed for altered substrate scope, as well as stereo- and regioselectivities. Furthermore, possible substrate promiscuity in engineered enzyme variants has also been addressed. In short, i). Paper I: three sub sites, each consisting of two-three amino acid residues within the active-site cavity were exposed to saturation mutagenesis in step-wise manner, coupled to an in vitro selection for improved catalytic activity with the unfavored (R)-1-phenylethanol. The observed stereoselectivity could be explained partly by a shift in nonproductive substrate binding. ii). Paper II is aimed specifically towards the improving the catalytic activity with aryl-substituted vicinal diols, such as (R)-1-phenylethane-1,2-diol, and the possibility to link the ADH-A reaction with a preceding epoxide hydrolysis to produce the acyloin 2-hydroxyacetophenone from rac-styrene oxide. iii). Paper III is mainly focused towards studies of regioselectivity. Here, ADH-A and engineered variants were challenged with a substrate containing two sec-alcohol functions and the cognate di-ketone. The regioselectivity in wild type as well as in engineered variants could in part be explained by a combination of experimental and computer simulations. iv). Paper IV is focused on elucidating possible effects on substrate promiscuities in engineered variants as compared to the wild type parent enzyme, when challenged with a spectrum of potential previously untested substrates.

    Download full text (pdf)
    fulltext
    Download (jpg)
    presentationsbild
1234 1 - 50 of 180
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf