Background: Microbial transformation of biomass into biofuels remains an important part of the United States’ strategy to reduce its dependency on fossil fuels. To produce ethanol from biomass microbes must be able to efficiently metabolize plant sugars into ethanol under industrial fermentation stresses. Naturally occurring microorganisms have not evolved to thrive in such industrial processes. Researchers have approached this problem by engineering strains that leverage the genetic strengths of select organisms to supplement the deficiencies in others. So far engineered strains have failed to maximize yields under industrial conditions. Continued strain discovery and optimization remains a vibrant research area. Technology Description: A UW–Madison researcher and others have modified a Lactobacillus casei strain that exhibits the highest ethanol conversion rates yet reported from the genus. L. casei naturally combines many characteristics of an ideal strain when compared to microorganisms typically considered for biofuel production like Saccharomyces cerevisiae Zymomonas mobilis Escherichia coli and Clostridium sp. which all suffer from various deficiencies. A L. casei strain exhibiting high conversion rates could represent a novel more efficient path to market for ethanol production. The modified bacterium is derived from L. casei strain 12A. It is made by (i) inactivating genes that encode a competing lactate enzyme and (ii) introducing genes from another organism (Zymomonas mobilis) that encode a pyruvate decarboxylase and an alcohol dehydrogenase II. Applications: 1) Biofuel (ethanol) production 2) Potential adaption to higher margin biochemical products and second generation biofuels such as isobutanol
1) Outperforms all other lactobacilli 2) L. casei 12A is an ideal candidate 3) Designated a GRAS (Generally Regarded As Safe) species 4) Amenable to genetic manipulation 5) Has relatively simple fermentative metabolism 6) Highly resistant to environmental stresses like high concentrations of acids biofuels and lignotoxins 7) Can utilize lignocellulose mono- and disaccharides 8) Can secrete and display proteins with potential for use in consolidated bioprocessing