Using Bacteria to Achieve High Solubilization of Biomass with Minimal Pretreatment
Thermophilic bacteria prove to be efficient biocatalysts for biomass solubilization.
A comprehensive comparison of lignocellulosic solubilization by various thermophilic bacteria to standard enzyme treatment found microbial solubilization of cellulosic biomass to be more effective, and enhanced by mechanical disruption.
Using thermophilic bacteria instead of expensive yeast enzymes to decompose biomass into its sugars for fermentation into biofuels will greatly reduce costs and potentially simplify the process.
Feedstock recalcitrance is the greatest barrier to cost-effective production of cellulosic biofuels. To overcome this recalcitrance, existing commercial cellulosic ethanol facilities employ thermochemical pretreatment with subsequent addition of fungal cellulase. However, processing cellulosic biomass without thermochemical pretreatment may be possible using thermophilic, cellulolytic bacteria. Researchers at the Department of Energy’s (DOE) BioEnergy Science Center (BESC) examined the ability of various thermophilic bacteria to solubilize autoclaved, but otherwise unpretreated cellulosic biomass. Carbohydrate solubilization of mid-season harvested switchgrass after 5 days ranged from 24 percent to 65 percent, with Clostridium thermocellum showing the best results among the four thermophiles tested. This finding was as much as fivefold better than with the standard method using a fungal cellulase cocktail and yeast fermentation. Other findings showed that there was equal fractional solubilization of glucan and xylan, and, importantly, that there was no biological solubilization of the noncarbohydrate fraction of biomass. A fivefold improvement over standard treatment was observed when using the most effective biocatalyst. Using thermophilic bacteria in biomass-solubilizing systems may enable a reduction in the amount of nonbiological processing required and, in particular, substitution of cotreatment for pretreatment.
This research was sponsored by BESC, a DOE Bioenergy Research Center supported by the Office of Biological and Environmental Research within DOE’s Office of Science. TYN was supported by the National Science Foundation. The generation of the CCRC series of plant cell wall glycan-directed monoclonal antibodies used was supported by NSF’s Plant Genome Program.
Paye, J. M. D., et al. 2016. “Biological Lignocellulose Solubilization: Comparative Evaluation of Biocatalysts and Enhancement via Cotreatment,” Biotechnology for Biofuels 9(8), DOI 10.1186/s13068-015-0412-y.