Biological pretreatment of rice straw by ligninolytic Bacillus sp. strains for enhancing biogas production

Fermenting agricultural biomass, such as rice straw (RS), to methane is a promising solution to an ongoing waste problem. However, the biomass must first be pretreated to break down lignin thereby increasing accessibility of the substrate to fermentative organisms. Biological pretreatment by microorganisms represents a potentially economical strategy to prepare the biomass for fermentation. We isolated seven candidate ligninolytic Bacillus sp. strains based on their robustness for lignin degradation. The production of the ligninolytic enzymes from these strains was characterized and optimized. The bacterial strains were tested for their ability to pretreat RS and increase the yield of biomethane fermentation. It was determined that using mixed combinations of bacterial cultures was more effective than using individual strains. Overall, the study demonstrates the potential of using these Bacillus sp. strains as robust biocatalysts for processing lignocellulosic waste biomass. Significance: Newly isolated Bacillus sp. strains demonstrated an efficient degradation of lignin, Azure B dye, fast hydrolysis of rice straw, and improved biogas yields. This research suggests that, Bacillus sp. strains could be a source of novel enzymes, and an ideal candidate in bioprocessing of complex substrates. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38:e13036, 2019