[Improving glycolic acid yield by metabolic engineering in Escherichia coli]

Glycolic acid is an important industrial compound. To improve glycolic acid yield, we knocked out ldhA (lactate dehydrogenase) in Escherichia coli MG1655 (DE3) to get the strain Mgly1. Then, we regulated expression levels of isocitrate lyase (aceA), glyoxylic acid reductase (ycdW) and isocitrate dehydrogenase kinase/phosphorylase (aceK) that are key enzymes of glycolate synthesis pathway. The yield of glycolic acid increased to 0.326 g/g glucose (38.3% of the theoretical yield) by overexpressing citrate synthase (gltA). Then we knocked out glcB and aceB (malate synthase) in Mgly1. The engineering strain Mgly335 was obtained and the yield of glycolic acid reached 0.522 g/g glucose (61.4% of the theoretical yield).