Elimination of Acetate Production to Improve Ethanol Yield During Continuous Synthesis Gas Fermentation by Engineered Biocatalyst Clostridium sp MTEtOH550

Acetogen strain sp. MT653 produced acetate 273 mM ( < 0.005) and ethanol 250 mM ( < 0.005) from synthesis gas blend mixture of 64 % CO and 36 % H-2. sp. MT653 was metabolically engineered to the biocatalyst strain sp. MTEtOH550. The biocatalyst increased ethanol yield to 590 mM with no acetate production during single-stage continuous syngas fermentation due to expression of synthetic cloned in a multi-copy number expression vector. The acetate production was eliminated by inactivation of the gene in sp. MTEtOH550. Gene introduction and gene elimination were achieved only using Syngas Biofuels Energy, Inc. electroporation generator. The electrotransformation efficiencies were 8.0 +/- 0.2 x 10(6) per microgram of transforming DNA of the expression vector at cell viability similar to 15 %. The frequency of suicidal vector integration to inactivate was similar to 10(-5) per the number of recipient cells. This is the first report on elimination of acetate production and overexpression of synthetic gene to engineer acetogen biocatalyst for selective biofuel ethanol production during continuous syngas fermentation.