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Aims: Culturing compost-derived microbial communities on biofuel feedstocks under industrial conditions is a technique to enrich for organisms and lignocellulolytic enzymes for bioenergy feedstock deconstruction. In this study, microbial communities from green waste compost (GWC) and grape pomace compost (GPC) were cultured on switchgrass and eucalyptus to observe the impact of inoculation on feedstock decomposition and microbial community structure., Methods and Results: Respiration was monitored as a measure of microbial activity, and 16S ribosomal RNA gene sequencing was used to characterize microbial community structure. The enriched community structure and respiration were influenced by the choice of feedstock, compost type, and application of thermophilic, high-solids conditions. However, the effect of compost source was significantly less than the effects of the other culture variables., Conclusions: Although there are subtle differences in potentially lignocellulolytic taxa between GPC- and GWC-derived communities, these differences do not affect the decomposition rates for these communities on switchgrass or eucalyptus., Significance and Impact of the Study: These results are useful for designing future experiments to discover lignocellulolytic micro-organisms from compost. They suggest that such work may be better served by deemphasizing screening of compost sources and instead focusing on how compost-derived communities adapt to the feedstocks and process conditions relevant to biofuel production., (© 2014 The Society for Applied Microbiology.)

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., (© 2012 UC Davis.)

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., (Journal of Applied Microbiology © 2011 The Society for Applied Microbiology. No claim to US Government works.)