Process Biochemistry, Vol.48, No.7, 1018-1024, 2013
Isolation and properties of beta-xylosidase from Aspergillus niger GS1 using corn pericarp upon solid state fermentation
There is growing interest in developing high-yield and low-cost production of xylanolytic enzymes for industrial applications using agroindustrial byproducts. A native strain of Aspergillus niger GS1 was used to produce beta-xylosidase (EC 22.214.171.124) on solid state fermentation using corn pericarp (CP) with innovative alkaline electrolyzed water (AEW) pretreatment at room temperature. beta-xylosidase was purified by ammonium sulfate fractionation followed by anion exchange and hydrophobic interaction chromatographies. beta-Xylosidase showed a molecular weight of 111 kDa, isoelectric point of 5.35 and specific ctivity of 386.7 U (mg protein)(-1), using beta-nitrophenyl-beta-b-xylopyranoside as substrate, at pH 5 and 60 degrees C, and optimal activity at pH 4.5. Optimal temperature was 65 C, showing full activity after 1 h at 60 degrees C. Activity was reduced by 1 mM beta-mercaptoethanol (55.6 0.1%), and enhanced by 1 mM SDS (11.0 +/- 0.03%). K-m and V-max were 6.1 0.9 mM and 1364 +/- 105 U (mg protein)(-1), respectively, whereas kat was 5.1 s(-1). A predominant alpha-helix (41%) was determined from circular dichroism on beta-xylosidase, while thermal transition profiles produced a T-m of 54.1 +/- 5.8 degrees C, enthalpy change for unfolding of 67.4 +/- 6.7 kJ/mol, and onset temperature of 37 degrees C. Pre-treatment of CP using AEW is an ecologically friendly alternative to chemical and heat treatments for the production of relatively high levels of beta-xylosidase. (C) 2013 Elsevier Ltd. All rights reserved.