Submitted to: Pacifichem Symposium
Publication Type: Abstract Only
Publication Acceptance Date: December 19, 2000
Publication Date: N/A
Technical Abstract: Development of suitable biocatalysts for the biomass to fuels and chemicals industry remains a significant technical challenge. We have developed a series of stable E. coli strains that convert biomass sugars to either L-lactate or ethanol by transforming nonfermentative strains with plasmids carrying either the lactate dehydrogenase (ldh) gene from Streptococcus bovis or alcohol dehydrogenase and pyruvate decarboxylase genes from Zymomonas mobilis. Under anaerobic conditions, these plasmids were retained in the absence of antibiotics by over 95% of the cells, and the modified strains produced L-lactate or ethanol at 90-93% of theoretical. We have also cloned a ldh gene from the fungus, Rhizopus oryzae, and developed genetic transformation methods for stable chromosomal integration. Recombinant R. oryzae strains had increased ldh activity and produced 30% more lactic acid than the parental wild-type with a concomitant decrease in both ethanol and fumarate byproducts.