Characterization of a novel bifunctional enzyme from buffalo rumen metagenome and its effect on in vitro ruminal fermentation and microbial community composition

To efficiently use lignocellulosic materials in ruminants, it is crucial to explore effective enzymes,especially bifunctional enzymes. In this study, a novel stable bifunctional cellulase-xylanase protein from buffalo rumen metagenome was expressed and characterized, Cel Xyn2. The enzyme displayed optimal activity at p H 6.0 and 45℃. The residual endoglucanase and xylanase activities were 90.6%and 86.4% after a 60-min pre-incubation at 55℃. Hydrolysis of rice straw, wheat straw, sheepgrass and sugar beet pulp by Cel Xyn2 showed its ability to degrade both cellulose and hemicellulose polymers. Treatment with Cel Xyn2 improved the hydrolysis of agricultural residues with an evident increase in production of total gas, lactate and volatile fatty acids. The results of 16S r RNA and realtime PCR showed that the effect on in vitro ruminal microbial community depended on fermentation substrates. This study demonstrated that Cel Xyn2 could strengthen lignocellulose hydrolysis and in vitro ruminal fermentation. These characteristics of Cel Xyn2 distinguish it as a promising candidate for agricultural application.