P80: Characterization of industrially relevant traits in bacteria isolated from carboxylate platform fermentations for biofuels

Microbial communities collected from 77 diverse soil environments in the continental United States, Hawaii, and Puerto Rico were screened in a biofuel fermentation process developed at Texas A&M (MixAlco™). From 34 of the fermentation communities selected based on superior performance within this screen, 1,866 bacterial isolates were cultured via a variety of conditions. Phylogenetic analysis of partial 16S rDNA sequences places 1,200 of these isolates in the genus Bacillus. Other genera include, but are not limited to: Ureibacillus, Anoxybacillus, Geobacillus, and Exiguobacterium. The central hypothesis of this study is that based on the saline and/or thermal conditions of the natural inocula, and also, survival during fermentation this collection likely harbors isolates with variation for industrially relevant traits. The phylogeny for this library was used to identify and prioritize the best candidate lineages for screens of extracellular cellulase activity, n-butanol tolerance, and lignin degradation, as indicated by decolorization of the surrogate Congo red. We used qualitative assays of extracellular cellulase production based on zones of clearing on carboxymethylcellulose (CMC) plates. We quantified tolerance to n-butanol by comparing the specific growth rate in the presence and absence of n-butanol. We assessed lignin degradation by measuring optical density of the isolates growing in Congo red. The variation we identified in these industrially relevant traits across isolates provides a proof of concept for both the existence of this variation in nature and the efficacy of employing fermentation and culturing approaches to enrich for these phenotypes.