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

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% [C2mim][OAc] was achieved, when the [C2mim][OAc] level was increased stepwise from 2% to 4% to 5% to 6%. Pyrosequencing results revealed a shift in the community and a sharp decrease in richness, when thermophilic conditions were applied. CONCLUSIONS: A community tolerant to a thermophilic, high-solids environment containing 6% [C2mim][OAc] was enriched from compost. Gradually increasing [C2mim][OAc] concentrations allowed the community to adapt to [C2mim][OAc]. SIGNIFICANCE AND IMPACT OF THE STUDY: A successful approach to enrich communities that decompose lignocellulose under thermophilic high-solids conditions in the presence of elevated levels of [C2mim][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, isolation and characterization of fungi tolerant to 1-ethyl-3-methylimidazolium acetate.

AIMS: This work aimed to characterize microbial tolerance to 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]), an ionic liquid that has emerged as a novel biomass pretreatment for lignocellulosic biomass. METHODS AND RESULTS: Enrichment experiments performed using inocula treated with [C2mim][OAc] under solid and liquid cultivation yielded fungal populations dominated by Aspergilli. Ionic liquid-tolerant Aspergillus isolates from these enrichments were capable of growing in a radial plate growth assay in the presence of 10% [C2mim][OAc]. When a [C2mim][OAc]-tolerant Aspergillus fumigatus strain was grown in the presence of switchgrass, endoglucanases and xylanases were secreted that retained residual enzymatic activity in the presence of 20% [C2mim][OAc]. CONCLUSIONS: The results of the study suggest that tolerance to ionic liquids is a general property of the Aspergilli. SIGNIFICANCE AND IMPACT OF THE STUDY: Tolerance to an industrially important ionic liquid was discovered in a fungal genera that is widely used in biotechnology, including biomass deconstruction.