Butanol and caproate production by consolidated bioprocessing after adaptive evolution of a fermentative microbial community

Abstract

Butanol production from cellulose by consolidated bioprocessing may accelerate the commercialization of lignocellulosic biofuels. This study applied adaptive evolution to a natural microbial community consisting of different taxa of fermenters and plant-degrading bacteria to increase its production of butanol. To this end, the parental microbial community was subjected to the stepwise enrichment of butanol at four initial concentrations in repeated-batch fermentations using pretreated corn stover as the sole substrate. After the adaptive evolution, the microbial community exposed to the highest concentration of butanol produced 13.8 g L-1 butanol, which was nine times higher than the parental microbial community. The adapted microbial community also produced the medium-chain fatty acid caproate (7.5 g L-1) from the condensation of alcohols (ethanol/butanol) with short-chain fatty acids at the end of the fermentation. A network analysis revealed that the largest subcommunities were represented by Clostridium sensu stricto 7 and Caproiciproducens, which are associated with the production of alcohols (ethanol/butanol) and medium-chain fatty acids, respectively. In the smaller subcommunities, Pseudomonas, Sutterella, and Pandoraea became more important after adaptive evolution, suggesting the production of extracellular polymeric substances and cross-stress protection as mechanisms of protection and adaptation against butanol. This study demonstrated that butanol production by the consolidated bioprocessing of cellulose required solventogenic bacteria, diverse taxa of plant-degrading bacteria that established unique interactions with the fermenters and, more important, members with mechanisms of protection and tolerance to solvents. © 2023 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.