Synthesis of citramalic acid from glycerol by metabolically engineered Escherichia coli.

Wu, Xianghao; Eiteman, Mark

Citramalic acid (citramalate) serves as a five-carbon precursor for the chemical synthesis of methacrylic acid. We compared citramalate and acetate accumulation from glycerol using Escherichia coli strains expressing a modified citramalate synthase gene cimA from Methanococcus jannaschii. These studies revealed that gltA coding citrate synthase, leuC coding 3-isopropylmalate dehydratase, and acetate pathway genes play important roles in elevating citramalate and minimizing acetate formation. Controlled 1.0 L batch experiments confirmed that deletions in all three acetate-production genes ( poxB, ackA, and pta) were necessary to reduce acetate formation to less than 1 g/L during citramalate production from 30 g/L glycerol. Fed-batch processes using MEC568/pZE12- cimA ( gltA leuC ackA- pta poxB) generated over 31 g/L citramalate and less than 2 g/L acetate from either purified or crude glycerol at yields exceeding 0.50 g citramalate/g glycerol in 132 h. These results hold promise for the viable formation of citramalate from unrefined glycerol.

ESCHERICHIA coli; METHANOCALDOCOCCUS jannaschii; GLYCERIN; CITRATE synthase; GENES

Journal of Industrial Microbiology & Biotechnology, 2017, Vol 44, Issue 10, p1483

1367-5435

Academic Journal

10.1007/s10295-017-1971-7