Analysis of an Ionic Liquid and Salt Tolerant Microbial Consortium Which Is Useful for Enhancement of Enzymatic Hydrolysis and Biogas Production

Abstract

Production of biofuels and biochemicals from lignocellulosic biomass via biorefining process requires both efficient pretreatment and cellulase enzymes to improve saccharification. Ionic liquid (IL) pretreatment is one of the competent methods to modify recalcitrant structures of lignocellulosic biomass, however, IL inhibits cellular metabolisms and cellulase activities. In this study, a lignocellulose degrading microbial consortium, named CT-1, was newly bred from saline soil sample by successive subcultivations and was cultured to produce IL-tolerant cellulase enzymes. The CT-1 showed high degradation activity on various cellulosic substrates, including rice straw, corn stover, and mixed vegetable residues. In the presence of 1 M of an IL, 1-ethyl-3-methylimidazolium acetate (EMIM-Ac), activity of cellulase produced from CT-1 remained more than 95% of non-IL condition. For application in biogas production, the CT-1 was mixed with activated wastewater sludge and rice straw residues in batch anaerobic digester. Addition of CT-1 enhanced biogas production for 6.5 times (170.92 mL/g-VS) compared to the control batch. The bacterial population distribution of CT-1 was analyzed by quantitative PCR with specific primers and the results showed that Bacteroidetes, Actinobacteria and Methanosarcinales were major members that corresponding with the activities of biomass degradation and biogas production. Overall, these results demonstrated the potential of CT-1 in biorefining process of lignocellulosic biomass with compatibility to IL pretreatment.