Enriching microbial communities and isolating microorganisms that thrive in a thermophilic, lignin-rich environment

Lignocellulose is one of the most abundant biomass resources on the planet making it an ideal feedstock for biofuel production. One major challenge associated with using lignocellulose is the presence and recalcitrance of lignin. Lignin is resistant to microbial degradation and its degradation products can be inhibitory to enzymes and microorganisms utilized in biomass conversion to biofuels. Even though lignin is resistant to degradation, there are microorganisms that have evolved to decompose it. White and brown rot fungi are the most well studied, however bacteria are promising because they have a wider tolerance to pH, temperature and oxygen limitations when compared to fungi. We hypothesize that there are bacteria capable of degrading lignin under high solids and thermophilic conditions, which would make these microbes industrially relevant. Experiments were carried out using high solid fermentation of Douglas fir over a period of 5 weeks to enrich for microorganisms that could efficiently breakdown lignin. Cellulase, hemicellulase and ligninase (ABTS) assays and respiration rates were used to assess enrichment, and microorganisms were isolated on lignin rich media. 16S rRNA gene sequencing was used to characterize the microbial community that developed with enrichment.  Results will be used to design systems for selecting lignin-degrading organisms and better understanding thermophilic bacterial communities that contribute to degradation of high-lignin feedstocks.