Methylglyoxal Bypass Identified as Source of Chiral Contamination in l(+) and d(−)-lactate Fermentations by Recombinant Escherichia coli
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- Grabar, T.B., Zhou, S., Shanmugam, K.T. et al. Biotechnol Lett (2006) 28: 1527. doi:10.1007/s10529-006-9122-7
Two new strains of Escherichia coli B were engineered for the production of lactate with no detectable chiral impurity. All chiral impurities were eliminated by deleting the synthase gene (msgA) that converts dihydroxyacetone-phosphate to methylglyoxal, a precursor for both l(+)- and d(−)-lactate. Strain TG113 contains only native genes and produced optically pure d(−)-lactate. Strain TG108 contains the ldhL gene from Pediococcus acidilactici and produced only l(+)-lactate. In mineral salts medium containing 1 mM betaine, both strains produced over 115 g (1.3 mol) lactate from 12% (w/v) glucose, >95% theoretical yield.