Acetogen biocatalyst Clostridium sp. MTEtOH871 engineered with our proprietary electrotransformation technology and equipment: continuous synthesis gas fermentation for selective ethanol production

Acetogen Clostridum sp. MT683 produced 272 mM acetate (p<0.005) and 263 mM ethanol (p<0.005) fermenting syngas (60% CO + 40% H2) in a single stage continuous fermentation with zero CO2 emission. Inactivation of phosphotransacetylase (pta) gene in Clostridium sp. MT683 eliminated acetate production and increased ethanol yield to 363 mM (p<0.005). Ethanol production in Clostridum sp. MT683 was further increased when the synthetic acetaldehyde dehydrogenase (aldh) from Clostridium ljungdahlii was cloned in the multi-copy expression vector in this strain. The resulted biocatalyst increased ethanol yield to 576 mM (p<0.005). Electrotransformation efficiencies were (9.30 + 0.15) x 106 transformants/μg of the expression vector DNA at cell viability ~15%. The integration frequency of pta inactivation was (2.12 + 0.02) x 10-5. Recorded in real time pulse current oscillations reflected the cell membranes electropermeabilization events. This is the first report on inactivation of pta and expression of synthetic aldh in the acetogen biocatalyst for selective biofuel ethanol production during continuous single step syngas fermentation.