Microbial production of glycolate from acetate by metabolically engineered Escherichia coli

Escherichia coli was metabolically engineered to synthesize glycolate using acetate as the carbon source. The native glyoxylate bypass pathway was reinforced by the overexpression of isocitrate lyase and isocitrate dehydrogenase kinase/phosphatase. Glyoxylate/hydroxypyruvate reductase was overexpressed to convert glyoxylate to glycolate. Meanwhile, side reactions were eliminated by inactivating genes encoding malate synthase, glyoxylate carboligase, and glycolate oxidase to prevent loss of glyoxylate and glycolate. The engineered E. coli produced 1.78 g/L glycolate from 3.23 g/L acetate after 48 h shake flask cultivation using minimal medium supplemented with 1 g/L yeast extract. When citrate synthase, phosphotransacetylase, and acetate kinase were co-overexpressed to strengthen the tricarboxylic acid cycle and acetate utilization, glycolate production titer was improved to 2.75 g/L with pH control in shake flasks. The results of this work offer an approach for producing glycolate using acetate as the carbon source.