Enriching and characterizing an aerotolerant mixed microbial community capable of cellulose hydrolysis and ethanol production

Abstract

Cellulosic ethanol produced via consolidated bioprocessing may one day be a viable alternative to fossil fuels However, efforts must focus on streamlining and simplifying its production in order to make this a reality. The aim of this study was to enrich a cellulolytic community and characterize its soluble end-products and bacterial diversity. The community degraded cellulose in the absence of reducing agent, and appeared to generate anaerobic conditions through oxygen-consuming aerobic respiration. Ethanol and acetate were the major fermentation products and the activity of the community was stable in aerobic and anaerobic media, as well as yeast extract-free aerobic media supplemented with other waste-based nutrient sources. Several community members showed high similarity to Clostridium species, suggesting the presence of some functional redundancy. Reducing agent and yeast extract both represent significant costs in the culturing of cellulolytic, ethanologenic microorganisms. The community described here exhibited this activity in the absence of both.