Thermophilic enrichment of microbial communities in the presence of the ionic liquid 1-ethyl-3-methylimidazolium acetate

Abstract

Aims: The aim of the study was to develop an approach to enrich ionic liquid tolerant micro-organisms that efficiently decompose lignocellulose in a thermophilic and high-solids environment. Methods and Results: High-solids incubations were conducted, using compost as an inoculum source, to enrich for thermophilic communities that decompose switchgrass in the presence of the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]). Ionic liquid levels were increased from 0 to 6% on a total weight basis incrementally. Successful enrichment of a community that decomposed lignocellulose at 55°C in the presence of 6% [OAc] has been developed. Communities yielded from this approach will provide resources for the discovery of enzymes and metabolic pathways relevant to biomass pretreatment and fuel production.

Enrichment of microbial communities tolerant to the ionic liquids tetrabutylphosphonium chloride and tributylethylphosphonium diethylphosphate

“…Gradual increases in tetra butyl and diethyl concentrations during the enrichment yielded communities capable of thriving on green waste in a high-solids, thermophilic environment in the presence of phosphonium ionic liquids. The gradual increases in IL concentration aided in microbial adaptation to the stressor, as advised by previous high-solids incubation studies with ionic liquids (Reddy et al 2012). Overall, increased tetra butyl and diethyl concentration caused a decline in microbial activity, as indicated by decreased respiration rates, which is consistent with prior thermophilic enrichments on switchgrass (Reddy et al 2012;Simmons et al 2014a).…”

“…The gradual increases in IL concentration aided in microbial adaptation to the stressor, as advised by previous high-solids incubation studies with ionic liquids (Reddy et al 2012). Overall, increased tetra butyl and diethyl concentration caused a decline in microbial activity, as indicated by decreased respiration rates, which is consistent with prior thermophilic enrichments on switchgrass (Reddy et al 2012;Simmons et al 2014a). Identification of the exact role of each organism in green waste decomposition requires further studies.…”

“…The VEGAN package in R software (http://CRAN.R-project.org/package=vegan) was used to perform ecological analyses to characterize enriched microbial communities as described elsewhere (Reddy et al 2012). Richness, Shannon index, and Pielou index of each community, as well as Bray…”

“…The resulting cellulose, hemicellulose, and lignin contents of the SGW were 28.9 % wt wt -1 , 17.9 % wt wt -1 , and 15.0 % wt wt -1 of dry matter respectively. Finished green waste compost was used as inoculum for enrichments based on prior success with community tolerance to IL (Reddy et al 2012); it was obtained from a commercial facility that composts agricultural residues including tree and vine prunings (Northern Recycling, Zamora, CA, USA). Compost was solar-dried and stored at room temperature until applied as inocula.…”

“…High-solids enrichments followed prior IL enrichments and were completed with stepwise increases in the concentrations of tetra butyl and diethyl (Reddy et al 2012). The enrichment pathways are presented in Figure 1.…”