title: Purification and characterization of three β-glycosidases exhibiting high glucose tolerance from Aspergillus niger ASKU28.
abstract: Production and utilization of cellulosic ethanol has been limited, partly due to the difficulty in degradation of cellulosic feedstock. β-Glucosidases convert cellobiose to glucose in the final step of cellulose degradation, but they are inhibited by high concentrations of glucose. Thus, in this study, we have screened, isolated, and characterized three β-glycosidases exhibiting highly glucose-tolerant property from Aspergillus niger ASKU28, namely β-xylosidase (P1.1), β-glucosidase (P1.2), and glucan 1,3-β-glucosidase (P2). Results from kinetic analysis, inhibition study, and hydrolysis of oligosaccharide substrates supported the identification of these enzymes by both LC/MS/MS analysis and nucleotide sequences. Moreover, the highly efficient P1.2 performed better than the commercial β-glucosidase preparation in cellulose saccharification, suggesting its potential applications in the cellulosic ethanol industry. These results shed light on the nature of highly glucose-tolerant β-glucosidase activities in A. niger, whose kinetic properties and identities have not been completely determined in any prior investigations.
authors.affiliation: a Interdisciplinary Graduate Program in Genetic Engineering, Faculty of Graduate School , Kasetsart University , Bangkok , Thailand.
authors.forename: Preeyanuch
authors.initials: P
authors.lastname: Thongpoo
authors.forename: Chantragan
authors.initials: C
authors.lastname: Srisomsap
authors.forename: Daranee
authors.initials: D
authors.lastname: Chokchaichamnankit
authors.forename: Vichien
authors.initials: V
authors.lastname: Kitpreechavanich
authors.forename: Jisnuson
authors.initials: J
authors.lastname: Svasti
authors.forename: Prachumporn T
authors.initials: PT
authors.lastname: Kongsaeree
mesh_terms: D001234:Aspergillus niger / Q000187:drug effects / Q000201:enzymology*; D002482:Cellulose / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D006868:Hydrolysis; D007700:Kinetics; D017421:Sequence Analysis; D001617:beta-Glucosidase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D002482:Cellulose; D001617:beta-Glucosidase; D005947:Glucose
keywords: Aspergillus niger; cellulose hydrolysis; glucose-tolerant; inhibition constant; β-glucosidase