Abstract:
Consolidated processing concept for biorefinery application has been developed to combine the pretreatment and hydrolysis of lignocellulosic biomass in one step. Previously, cellulase-producing microbial consortium KS-22 was screened and enriched from salted soil in Thailand. In this study, the activity of cellulase produced from KS-22 was observed in buffer containing an ionic liquid (IL), so called EMIM-Ac, at 20% EMIM-Ac concentration. The result showed that the cellulase activity was reduced to 63.63%, which was higher than that of commercial cellulase, CelluClast 1.5L, for 2.65 in the same condition. KS-22 cellulase was further characterized for the optimal condition to be at 55 °C, pH 4.0 for enzymatic hydrolysis reaction. The enzymatic kinetic study based on Michaelis-Menten equation and Line-Weaver Burk plot showed that Km and Vmax were 1,727.180 uM and 0.603 mM/min. When EMIM-Ac was added into the reaction, Km and Vmax were reduced. KS-22 cellulase was fractionated with Sephacryl S-100 column chromatrography and the active fractions were analyzed for endoglucanase, exoglucanase and beta-glucosidase activities. The endoglucanase active fraction appeared to have 40 kDa size in SDS-PAGE and zymogram analysis. Then KS-22 cellulase was applied in consolidated reactions of rice straw pretreatment and hydrolysis with EMIM-Ac. When EMIM-Ac absent, the specific enzyme activity of KS-22 cellulase was 0.090 U/mg. The specific enzyme activity of KS-22 cellulase was increased to 0.320 U/mg in consolidated reaction containing 2.0 M EMIM-Ac, which was higher than CelluClast 1.5L for 10 times in the same condition. In addition, KS-22 culture could improve the production of biogas from rice straw for 1.71 time compared to control set. Altogether, this study demonstrate the potential application of KS-22 in consolidated biorefinery of lignocellulosic biomass by combining pretreatment and hydrolysis reactions in the same reactor successfully.