Submitted to: Biotechnology for Fuels and Chemicals Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 4, 2005
Publication Date: May 4, 2005
Citation: Liu, S., Nichols, N.N., Dien, B.S., Cotta, M.A. 2005. Ethanol fermentation by overexpressing a Gram-positive PDC gene in Lactobacillus plantarum strain TF103 [abstract]. Biotechnology for Fuels and Chemicals Symposium Proceedings, May 1-4, 2005, Denver, Colorado. p. 158. Technical Abstract: The objective of the current research is to convert the lactic acid fermentation capacities of select strains of lactic acid bacteria (LAB) into that of ethanol production. Lactobacillus plantarum ferments glucose to pyruvate through the Embden-Meyerhof-Parnas pathway, and pyruvate is then converted into lactate via lactate dehydrogenase (LDH). By substituting LDH with pyruvate decarboxylase (PDC) activity, pyruvate may be redirected away from lactic acid and toward ethanol. A pyruvate decarboxylase gene from the Gram-positive bacterium Sarcina ventriculi (Spdc) was introduced into a LDH deficient strain L. plantarum TF103 in which both ldhL and ldhD genes were inactivated. Four different fusion constructs between Spdc and either the S. ventriculi promoter or the Lactococcus lactis promoter in pTRKH2 were introduced into TF103. PDC activity was detected in all four recombinant strains. The engineered strains were examined for ethanol and other metabolite products in flask fermentations. The recombinant strains grew slowly and produced 90-170 mM ethanol. An alternative approach to facilitate growth and increase ethanol production might be to insert pdc and inactivate ldh simultaneously by direct gene replacement.