Recovery of Biomass Energy on the Farm: Identification of Cellulolytic Bacteria in Agricultural Residues for On-Site Bioethanol Production

Abstract

Farms are significant sources of unused biomass, conversion of which into energy would contribute to decreasing the environmental footprint associated with farming activities. A promising alternative for energy conversion involves bioethanol production. Bioethanol can be fermented from simple sugars that in turn must be extracted from biomass. To this end cocktails of enzymes may be used to deconstruct lignocellulosic biomass, but their cost and efficiency are often prohibitive. One could circumvent these drawbacks by finding locally-established, well adapted bacteria that produce enzymes with relevant specificities.  Here we identified such bacteria and compared their ability to hydrolyse cellulose from agricultural and industrial biomass residues. By collecting environmental samples at a local farm we identified 54 strains, of which 12 exhibited cellulolytic activity. Based on 16S rDNA sequence analyses, we found that these strains were relatives of Bacillus aryabhattai, B. cereus, B. licheniformis, B. pseudomycoides and B. thuringiensis species. This article reveals the first experimental evidence of cellulase activity from B. aryabhattai, confirming earlier predictions. The abilities of these strains to produce simple sugars from carboxymethyl cellulose, treated maize biomass, and papermaking primary sludge were investigated. B. licheniformis and B. thuringiensis related strains both showed high extracellular cellulase activity and sugar production when grown on treated maize.  This study suggests that local microbial biodiversity should be considered when developing enzymatic strategies for exploitation of farm residues.