Bioenergy feedstock‐specific enrichment of microbial populations during high‐solids thermophilic deconstruction

Abstract

Thermophilic microbial communities that are active in a high-solids environment offer great potential for the discovery of industrially relevant enzymes that efficiently deconstruct bioenergy feedstocks. In this study, finished green waste compost was used as an inoculum source to enrich microbial communities and associated enzymes that hydrolyze cellulose and hemicellulose during thermophilic high-solids fermentation of the bioenergy feedstocks switchgrass and corn stover. Methods involving the disruption of enzyme and plant cell wall polysaccharide interactions were developed to recover xylanase and endoglucanase activity from deconstructed solids. Xylanase and endoglucanase activity increased by more than a factor of 5, upon four successive enrichments on switchgrass. Overall, the changes for switchgrass were more pronounced than for corn stover; solids reduction between the first and second enrichments increased by a factor of four for switchgrass while solids reduction remained relatively constant for corn stover. Amplicon pyrosequencing analysis of small-subunit ribosomal RNA genes recovered from enriched samples indicated rapid changes in the microbial communities between the first and second enrichment with the simplified communities achieved by the third enrichment. The results demonstrate a successful approach for enrichment of unique microbial communities and enzymes active in a thermophilic high-solids environment.

Efficient anaerobic transformation of raw wheat straw by a robust cow rumen-derived microbial consortium

“…corn stover) in only 4 cycles(Reddy et al, 2011). Remarkably, in this study it was shown that the main changes occurred between the first and second enrichment cycles, since thereafter both the function and the community structure remained quite stable.…”

Global transcriptome response to ionic liquid by a tropical rain forest soil bacterium,Enterobacter lignolyticus

“…Utilization of microorganisms isolated from natural environments, such as tropical rain forest (23) soil, can greatly improve the current biofuels strategy. Natural microbial communities that degrade biomass are often exposed to fluctuating environmental conditions, and thus represent a vast resource for both stress-tolerant organisms and highly efficient, stable lignocellulolytic enzymes (23)(24)(25).…”

Ionic Liquids Impact the Bioenergy Feedstock-Degrading Microbiome and Transcription of Enzymes Relevant to Polysaccharide Hydrolysis

“…Incubations were conducted as described previously (14, 24). In summary, switchgrass was wetted with minimal media (25) to a moisture content of 400% (wt) dry basis (g water [g dry solid] −1 ), inoculated with 10% (wt) inoculum (g dry inoculum [g dry solid] −1 ), and then amended with IL.…”

“…Enzymes were extracted from final feedstocks with a buffer containing 1% (wt) sodium chloride, 0.1% (wt) Tween 80, and 50% (wt) ethylene glycol (24). Freshly collected final feedstock (3 g wet weight) was shaken with 27 g of buffer for 1 h at 150 rpm and ambient temperature.…”

“…The extraction buffer was exchanged with sodium acetate buffer (50 mM, pH 5.0) using Vivaspin columns (VWR, West Chester, PA) with a polyethersulfone (PES) membrane and a molecular weight cutoff value of 5. Endoglucanase and xylanase activities in dialyzed extracts were measured as described previously (24). All enzyme extractions and assays were completed in triplicate.…”