Re-engineering Escherichia coli for ethanol production
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A lactate producing derivative of Escherichia coli KO11, strain SZ110, was re-engineered for ethanol production by deleting genes encoding all fermentative routes for NADH and randomly inserting a promoterless mini-Tn5 cassette (transpososome) containing the complete Zymomonas mobilis ethanol pathway (pdc, adhA, and adhB) into the chromosome. By selecting for fermentative growth in mineral salts medium containing xylose, a highly productive strain was isolated in which the ethanol cassette had been integrated behind the rrlE promoter, designated strain LY160 (KO11, Δfrd::celY Ec ΔadhE ΔldhA, ΔackA lacA::casAB Ko rrlE::(pdc Zm -adhA Zm -adhB Zm -FRT-rrlE) pflB + ). This strain fermented 9% (w/v) xylose to 4% (w/v) ethanol in 48 h in mineral salts medium, nearly equal to the performance of KO11 with Luria broth.
KeywordsBetaine E. coli Ethanol Lactate Osmotic stress
This research was supported by grants from the U.S. Department of Agriculture (01-35504-10669 and 00-52104-9704), the U.S. Department of Energy (FG02-96ER20222 and FG36-04GO14019), and by the Verenium Corporation.
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