title: Effect of the inactivation of lactate dehydrogenase, ethanol dehydrogenase, and phosphotransacetylase on 2,3-butanediol production in Klebsiella pneumoniae strain.
abstract: BACKGROUND
  2,3-Butanediol (2,3-BD) is a high-value chemical usually produced petrochemically but which can also be synthesized by some bacteria. To date, Klebsiella pneumoniae is the most powerful 2,3-BD producer which can utilize a wide range of substrates. However, many by-products are also produced by K. pneumoniae, such as ethanol, lactate, and acetate, which negatively regulate the 2,3-BD yield and increase the costs of downstream separation and purification.
  
  
  RESULTS
  In this study, we constructed K. pneumoniae mutants with lactate dehydrogenase (LDH), acetaldehyde dehydrogenase (ADH), and phosphotransacetylase (PTA) deletion individually by suicide vector conjugation.These mutants showed different behavior of production formation. Knock out of ldhA had little influence on the yield of 2,3-BD, whereas knock out of adhE or pta significantly improved the formation of 2,3-BD. The accumulation of the intermediate of 2,3-BD biosynthesis, acetoin, was decreased in all the mutants. The mutants were then tested in five different carbon sources and increased 2,3-BD was observed. Also a double mutant strain with deletion of adhE and ldhA was constructed which resulted in accelerated fermentation and higher 2,3-BD production. In fed-batch culture this strain achieved more than 100 g/L 2,3-BD from glucose with a relatively high yield of 0.49 g/g.
  
  
  CONCLUSIONS
  2,3-BD production was dramatically improved with the inactivation of adhE and pta. The inactivation of ldhA could advance faster cell growth and shorter fermentation time. The double mutant strain with deletion of adhE and ldhA resulted in accelerated fermentation and higher 2,3-BD production. These results provide new insights for industrial production of 2,3-BD by K. pneumoniae.
authors.forename: Xuewu
authors.initials: X
authors.lastname: Guo
authors.forename: Chunhong
authors.initials: C
authors.lastname: Cao
authors.forename: Yazhou
authors.initials: Y
authors.lastname: Wang
authors.forename: Chaoqun
authors.initials: C
authors.lastname: Li
authors.forename: Mingyue
authors.initials: M
authors.lastname: Wu
authors.forename: Yefu
authors.initials: Y
authors.lastname: Chen
authors.forename: Cuiying
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education; Tianjin Industrial Microbiology Key Lab, College of Biotechnology, Tianjin University of Science and Technology, Box 08, No, 29, 13ST, TEDA, Tianjin 300457, China. peihuadong@hotmail.com.
authors.forename: Huadong
authors.initials: H
authors.lastname: Pei
authors.forename: Dongguang
authors.initials: D
authors.lastname: Xiao