Use of microbial consortia for anaerobic digestion of lignocellulosic biomass for production of mixed carboxylic acids

Lignocellulosic biomass has gained attention in recent times as a source of bioproducts and biofuels due to its low cost and widespread availability, but conversion costs remain high. Mixed culture anaerobic digestion can achieve lower cost conversion, but the normal biogas product (CH4 +CO2) is of low value. In this study, biomass resources such as immature switchgrass and pretreated willow wood were used to produce carboxylic acids through anaerobic acidogenic digestion.  Prior work has shown these acids can be separated and recovered with nanofiltration.

The biomass was digested using a mixed culture of microorganisms in anaerobic conditions. The inoculum consisted of a mixture of silage, rumen fluid and compost. This rich mixture of microorganisms was monitored and sampled regularly during the digestion process. The microbial DNA was extracted, sequenced using 16s rRNA sequencing technique and analyzed using statistical and bioinformatics tools. 

Our results indicated the microbial consortium primarily consisted of Clostridia sp, Prevotella sp and Lactobacilli. These microbial populations are known for their cellulose-degrading and/or acid-producing properties. Therefore, the results indicate that the microbial consortium consists of cellulose-degrading and acid-producing microorganisms that are working together to enhance biomass conversion into mixed carboxylic acids.