title: [Production of L-lactic acid from pentose by a genetically engineered Escherichia coli].
abstract: OBJECTIVE
  In this study, we constructed a recombinant Escherichia coli strain for the production of high-purity L-lactic acid, using a homoethanol fermenting mutant E. coli SZ470 (deltafrdBC deltaldhA deltaackA deltafocA-pflB deltapdhR: :pflBp6-pflBrbs-aceEF-lpd) as the starting strain.
  
  
  METHODS
  By using homologous recombination, we deleted the adhE gene from SZ470 to obtain a mutant Escherichia coli JH01, which could not grow under anaerobic conditions. Then we cloned the L-lactate dehydrogenase gene (ldhL) of Pediococcus acidilactici and inserted it into the chromosome of JH01 via electroporation to obtain a recombinant strain Escherichia coli JH12. We evaluated the L-lactic acid production of the recombinant strain in a 15 L fermenter.
  
  
  RESULTS
  In 10 L LB medium supplemented with 6% glucose, JH12 maintained maximal cell growth and an efficient L-lactic acid production rate for 36 h. Glucose consumption rate achieved was 1.46 g/(L x h) and L-lactic acid production rate was 1.14 g/(L x h). The results also show that 41.13 g/L lactic acid was produced, achieving a purity of 95.69% (based on total fermentation products). Xylose consumption rate was 0.88 g/(L x h) and L-lactic acid production rate was 0.60 g/(L x h). The production of lactic acid was 34.73 g/L, achieving a purity of 98%. There were no succinic acid and formic acid detected and only little amount of acetic acid generated during the fermentation.
  
  
  CONCLUSIONS
  We constructed a homolactic acid fermentation strain E. coli JH12, which could efficiently convert glucose and xylose into high-purity L-lactic acid. JH12 could have great potential in industrial fermentation for L-lactic acid production.
authors.affiliation: Key Laboratory of Fermentation Engineering of Ministry of Education, Hubei University of Technology, Wuhan 430068, China. jinfangzhao@126.com
authors.forename: Jinfang
authors.initials: J
authors.lastname: Zhao
authors.forename: Liyuan
authors.initials: L
authors.lastname: Xu
authors.forename: Yongze
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiao
authors.initials: X
authors.lastname: Zhao
authors.forename: Jinhua
authors.initials: J
authors.lastname: Wang
mesh_terms: D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005285:Fermentation / Q000235:genetics / Q000502:physiology; D005818:Genetic Engineering / Q000379:methods; D005947:Glucose / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000096:biosynthesis* / Q000378:metabolism; D010376:Pediococcus / Q000235:genetics / Q000378:metabolism; D010429:Pentoses / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D010429:Pentoses; D019344:Lactic Acid; D014994:Xylose; D000426:Alcohol Dehydrogenase; C068383:adhE protein, E coli; D007770:L-Lactate Dehydrogenase; D000445:Aldehyde Oxidoreductases; D005947:Glucose