Simplified aerobic and anaerobic microbiotas derived from compost for efficient degradation of cellulosic biomasses

The high cost of commercial enzymes for depolymerizing fermentable carbohydrates of lignocellulosic biomass represents one of the main drawbacks to its use as a renewable feedstock to produce bioenergy and bioproducts. This work employs the dilution-to-stimulation method to produce simplified microbiotas with a high capacity for cellulose degradation. These microbiotas were obtained from four lignocellulosic composts cultivated under aerobic and anaerobic conditions during ten transfers using carboxymethylcellulose (CMC) as carbon source. After the eighth transfer, the depolymerization percentage of CMC reached the same values (70 ± 3%) for all microbiotas and respiration conditions. The microbial structure of all enriched microbiotas was simplified, mostly to Lactobacillus and Clostridium in anaerobic conditions while the more diverse aerobic enriched microbiotas were composed mainly of Rhizobium, Enterobacter, Alcaligenes, and Enterococcus. After the enrichment process, the two enriched microbiotas were grown on four biologically-pretreated xylan-free lignocellulosic biomasses achieving a maximum cellulose degradation rate of 0.063 g/L-h, and 0.061 g/L-h, respectively. These cellulose-degrading microbiotas are a promising alternative to high-cost enzymes for their capacity to obtain fermentable sugars from different lignocellulosic biomasses that could be used in synergy with selected fermenting bacteria to obtain a desired fermentation product.