Bioprocessing from crude biomass feedstocks requires pretreatment to remove lignin, enzymatic hydrolysis of cellulose and hemicellulose into sugars, and fermentation to produce value-added chemicals. Consolidated bioprocessing seeks to minimize the steps required to get from biomass to product, typically by combining hydrolysis and production with one engineered strain or a collection of strains in a consortium. However, these approaches still rely on pretreatment to remove lignin from biomass. Anaerobic gut fungi thrive on crude biomass without any pretreatment, but cannot yet be engineered for production. However, when grown in batch culture on pure cellulose, up to 50% of biopolymer is converted to excess free glucose not consumed by the fungi. On crude lignocellulose, only 10% of cellulose is converted to excess glucose, but additional sugars are also released from hemicellulose to support microbial growth. The availability of sugars can be predicted from the transcriptomic/genomic reconstruction of sugar catabolic pathways to determine which sugars will be consumed by the fungi. While gut fungi possess the enzymes required to hydrolyze cellulose and hemicellulose, they cannot catabolize all of these sugars. Of note, arabinose and galactose catabolism is incomplete and despite a complete xylose catabolic pathway, the fungi do not subsist on pentose sugar in isolation. Here, we determine the diversity of carbohydrates that remain after fungal growth to guide co-culture strategies where microbes will consume leftover sugars from hydrolysates. Furthermore, by pairing gut fungi with production-capable microbes, we aim to reduce catabolite repression and competition, providing a path forward for stable production directly from crude biomass.<br/>

Consolidating pretreatment and hydrolysis with engineered microbial consortia

253rd National Meeting (2017)

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