title: Homofermentative production of D- or L-lactate in metabolically engineered Escherichia coli RR1.
abstract: We investigated metabolic engineering of fermentation pathways in Escherichia coli for production of optically pure D- or L-lactate. Several pta mutant strains were examined, and a pta mutant of E. coli RR1 which was deficient in the phosphotransacetylase of the Pta-AckA pathway was found to metabolize glucose to D-lactate and to produce a small amount of succinate by-product under anaerobic conditions. An additional mutation in ppc made the mutant produce D-lactate like a homofermentative lactic acid bacterium. When the pta ppc double mutant was grown to higher biomass concentrations under aerobic conditions before it shifted to the anaerobic phase of D-lactate production, more than 62.2 g of D-lactate per liter was produced in 60 h, and the volumetric productivity was 1.04 g/liter/h. To examine whether the blocked acetate flux could be reoriented to a nonindigenous L-lactate pathway, an L-lactate dehydrogenase gene from Lactobacillus casei was introduced into a pta ldhA strain which lacked phosphotransacetylase and D-lactate dehydrogenase. This recombinant strain was able to metabolize glucose to L-lactate as the major fermentation product, and up to 45 g of L-lactate per liter was produced in 67 h. These results demonstrate that the central fermentation metabolism of E. coli can be reoriented to the production of D-lactate, an indigenous fermentation product, or to the production of L-lactate, a nonindigenous fermentation product.
authors: Bioprocess Engineering Division, Korea Research Institute of Bioscience and Biotechnology, Yusong, Taejon 305-600, Korea.
authors: D E
authors: DE
authors: Chang
authors: H C
authors: HC
authors: Jung
authors: J S
authors: JS
authors: Rhee
authors: J G
authors: JG
authors: Pan
mesh_terms: D000084:Acetate Kinase / Q000235:genetics / Q000378:metabolism; D000085:Acetates / Q000378:metabolism; D000332:Aerobiosis; D000693:Anaerobiosis; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D005285:Fermentation; D005818:Genetic Engineering; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000096:biosynthesis*; D007780:Lacticaseibacillus casei / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D010709:Phosphate Acetyltransferase / Q000235:genetics / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D013237:Stereoisomerism; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D000085:Acetates; D019344:Lactic Acid; D019802:Succinic Acid; D007770:L-Lactate Dehydrogenase; D010709:Phosphate Acetyltransferase; D000084:Acetate Kinase; D010730:Phosphoenolpyruvate Carboxylase