Rumen-Targeted Mining of Enzymes for Bioenergy Production

Second-generation biofuel production, which aims to convert lignocellulose to liquid transportation fuels, could be transformative in worldwide energy portfolios. A bottleneck impeding its large-scale deployment is conversion of the target polysaccharides in lignocellulose to their unit sugars for microbial fermentation to the desired fuels. Cellulose and hemicellulose, the two major polysaccharides in lignocellulose, are complex in nature, and their interactions with pectin and lignin further increase their recalcitrance to depolymerization. This review focuses on the intricate linkages present in the feedstocks of interest and examines the potential of the enzymes evolved by microbes, in the microbe/ruminant symbiotic relationship, to depolymerize the target polysaccharides. We further provide insights to how a rational and more efficient assembly of rumen microbial enzymes can be reconstituted for lignocellulose degradation. We conclude by expounding on how gains in this area can impact the sustainability of both animal agriculture and the energy sector.