title: Recombinant Escherichia coli engineered for production of L-lactic acid from hexose and pentose sugars.
abstract: Recombinant Escherichia coli have been constructed for the conversion of glucose as well as pentose sugars into L-lactic acid. The strains carry the lactate dehydrogenase gene from Streptococcus bovis on a low copy number plasmid for production of L-lactate. Three E. coli strains were transformed with the plasmid for producing L-lactic acid. Strains FBR9 and FBR11 were serially transferred 10 times in anaerobic cultures in sugar-limited medium containing glucose or xylose without selective antibiotic. An average of 96% of both FBR9 and FBR11 cells maintained pVALDH1 in anaerobic cultures. The fermentation performances of FBR9, FBR10, and FBR11 were compared in pH-controlled batch fermentations with medium containing 10% w/v glucose. Fermentation results were superior for FBR11, an E. coli B strain, compared to those observed for FBR9 or FBR10. FBR11 exhausted the glucose within 30 h, and the maximum lactic acid concentration (7.32% w/v) was 93% of the theoretical maximum. The other side-products detected were cell mass and succinic acid (0.5 g/l).
authors.affiliation: Fermentation Biochemistry Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 North University Street, Peoria, IL 61604, USA.
authors.forename: B S
authors.initials: BS
authors.lastname: Dien
authors.forename: N N
authors.initials: NN
authors.lastname: Nichols
authors.forename: R J
authors.initials: RJ
authors.lastname: Bothast
mesh_terms: D003470:Culture Media; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005285:Fermentation; D005818:Genetic Engineering / Q000379:methods*; D005947:Glucose / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000096:biosynthesis*; D010957:Plasmids / Q000235:genetics; D011995:Recombination, Genetic; D016985:Streptococcus bovis / Q000201:enzymology / Q000235:genetics; D014994:Xylose / Q000378:metabolism*
chemical_list: D003470:Culture Media; D019344:Lactic Acid; D014994:Xylose; D007770:L-Lactate Dehydrogenase; D005947:Glucose