Over Production of Lactate in E.coli Engineered With an Acrylate Pathway
Lactic acid is widely used in the food, cosmetic, pharmaceutical, and chemical industries and has received increased attention for use as a monomer for the production of bio-degradable polylactic acid. It can be produced by either biotechnological fermentation or chemical synthesis, but the former route has received considerable interest recently, due to environmental concerns and the limited nature of petrochemical feed stocks.The recombinant E. coli VK-23 encoding the enzymes of acrylate pathway (lactoyl- CoA dehydratase, acryloyl- CoA reductase and propionyl-CoA transferase) has been demonstrated earlier for overproduction of lactic acid. In this study we intend to find out the enzymes responsible for lactate overproduction and to improve the lactate productivity levels by using fed-batch bioreactor. A maximum productivity level of up to 24.2g l− 1 (% of yield 96%) in 14 hours was obtained with maximum specific and volumetric productivity of 0.8 g g- 1h-1 and 2.4 g l− 1 h− 1 respectively. The productivity levels attained seemed to be comparatively similar with that of metabolically engineered lactic acid overproducers. This recombinant E. coli with a new acrylate pathway has great potential to meet the growing market demand of fermentation based lactic acid production due to high growth rate and tolerance to organic acids.