title: Binding characteristics and synergistic effects of bacterial expansins on cellulosic and hemicellulosic substrates.
abstract: Expansins are non-catalytic proteins which loosen plant cell wall structure. In this study, binding kinetics and synergistic action of five bacterial expansins on cellulosic and hemicellulosic polysaccharides were studied. The expansins differed in binding capacity (Bmax) and affinity (Kd) for different substrates. A common pattern of binding efficiency (Bmax/Kd) was found among the expansins tested, in which efficiency was greatest for the phosphoric acid-swollen cellulose (PASC), then the hemicellulose arabinoxylan followed by the microcrystalline cellulose (Avicel PH101). The expansins enhanced the action of Trichoderma reesei cellulase/hemicellulase mixture for degrading all three substrates to varying degrees. Among the substrates and expansins tested, BpEX from Bacillus pumilus and CmEX from Clavibacter michiganensis showed the greatest enhancement effect on arabinoxylan with 11.4 and 12.2-fold greater reducing sugar yield than the reaction with enzyme alone. The work gives insights into the wider application of expansins on enhancing polysaccharide hydrolysis, particularly on hemicellulosic substrates.
authors.affiliation: Department of Genetics, Faculty of Sciences, Kasetsart University, Chatuchak, Bangkok 10900, Thailand.
authors.forename: Benjarat
authors.initials: B
authors.lastname: Bunterngsook
authors.affiliation: Enzyme Technology Laboratory, Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Khlong Luang, Pathum Thani 12120, Thailand. Electronic address: lily@biotec.or.th.
authors.forename: Lily
authors.initials: L
authors.lastname: Eurwilaichitr
authors.affiliation: Department of Genetics, Faculty of Sciences, Kasetsart University, Chatuchak, Bangkok 10900, Thailand.
authors.forename: Arinthip
authors.initials: A
authors.lastname: Thamchaipenet
authors.affiliation: Enzyme Technology Laboratory, Bioresources Technology Unit, National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Khlong Luang, Pathum Thani 12120, Thailand.
authors.forename: Verawat
authors.initials: V
authors.lastname: Champreda
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism*; D003001:Cloning, Molecular; D005822:Genetic Vectors / Q000235:genetics; D006868:Hydrolysis; D007700:Kinetics; D011134:Polysaccharides / Q000378:metabolism*; D011485:Protein Binding; D012394:Rosaniline Dyes; D014961:X-Ray Diffraction; D014990:Xylans / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011134:Polysaccharides; D012394:Rosaniline Dyes; D014990:Xylans; C048139:Coomassie blue; C007916:hemicellulose; D002482:Cellulose; C085118:arabinoxylan
keywords: Binding kinetics; Expansin; Glycosyl hydrolases; Lignocellulose; Synergy