Elimination of Acetate Production to Improve Ethanol Yield During Continuous Synthesis Gas Fermentation by Engineered Biocatalyst Clostridium sp. MTEtOH550
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Acetogen strain Clostridum sp. MT653 produced acetate 273 mM (p < 0.005) and ethanol 250 mM (p < 0.005) from synthesis gas blend mixture of 64 % CO and 36 % H2. Clostridum sp. MT653 was metabolically engineered to the biocatalyst strain Clostridium 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 adh cloned in a multi-copy number expression vector. The acetate production was eliminated by inactivation of the pta gene in Clostridium 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 × 106 per microgram of transforming DNA of the expression vector at cell viability ~15 %. The frequency of suicidal vector integration to inactivate pta was ~10−5 per the number of recipient cells. This is the first report on elimination of acetate production and overexpression of synthetic adh gene to engineer acetogen biocatalyst for selective biofuel ethanol production during continuous syngas fermentation.
KeywordsAcetogens PTA inactivation Synthetic ADH Ethanol production Syngas fermentation Electrotransformation
The research was supported by the funds of Syngas Biofuels Energy, Inc. Syngas Biofuels Energy, Inc. is the sole distributor of the electroporation and electrofusion equipment: www.syngasbiofuelsenergy.com.
Conflict of Interest
The authors declare that they have no conflict of interest.
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