Change in Cellulase Activity during Pretreatment with Rumen Fluid for the Anaerobic Digestion of Lignocellulosic Biomass

摘要

Pretreatment with rumen fluid discharged from slaughterhouses effectively enhances methane production from lignocelluosic biomass. We investigated which cellulose-degrading enzymes retained high degradative activity during pretreatment with rumen fluid. Carboxymethyl cellulose (CMC) was pretreated with rumen fluid at 37°C for 48 hours. During the pretreatment, the CMC was digested into volatile fatty acids (VFAs) and converted into biogasses, principally CO_2 and CH4. Accumulation of VFAs significantly decreased the value of pH during the first 24 hours. The total solid digestion rate (g/h) of the CMC increased for the first 24 hours. Protein concentration included in rumen fluid decreased with the pretreatment time. We used SDS-PAGE and CMC zymograms to identify the carboxymethyl cellulases (CMCases) with high enzyme activity during the pretreatment. The number of CMCases revealed by the zymograms increased for the first 24 hours, and different CMCases showed high activity depending on the pretreatment time. Our results demonstrated the dynamics of key cellulose-degrading enzymes during the pretreatment with rumen fluid.