title: Efficient 1,3-propanediol production by fed-batch culture of Klebsiella Pneumoniae: the role of pH fluctuation.
abstract: The fermentative production of 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae under different fed-batch strategies was investigated. pH-stat fed-batch strategies proved to be not effective for economical 1,3-PD production for the existence of relatively high concentration of byproducts and residual glycerol at the end of the fermentation. However, in the pH-stat fed-batch strategy, an important phenomenon was observed that the yields of two main byproducts, 2,3-butanediol and lactic acid, were closely related to pH value. The dominant byproduct was 2,3-butanediol at a pH value of 5.0 to 6.5 but changed to be lactic acid at a pH value of 7.1 to 8.0. Based on the analysis of the phenomenon, a self-protection mechanism in K. pneumoniae, namely that the growing K. pneumoniae cells switch the metabolic pathways responding to environmental pH changes, was proposed. Thus a kind of feeding strategy was further applied during which the pH value was fluctuated between 6.3 and 7.3 periodically by feeding glycerol-ammonia mixture and sulphuric acid to make the metabolic pathways of 2,3-butanediol and lactic acid sub-active under the periodical low or high pH stress. At last, efficient 1,3-PD production was fulfilled under this fed-batch strategy, and the best results were achieved leading to 70 g/l 1,3-PD with a yield of 0.70 mol/mol glycerol and productivity of 0.97 g/l/h, while the two main byproducts and residual glycerol were under low concentrations.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Life Science and Pharmacy, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing, People's Republic of China.
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Ji
authors.forename: He
authors.initials: H
authors.lastname: Huang
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Zhu
authors.forename: Nan
authors.initials: N
authors.lastname: Hu
authors.forename: Shuang
authors.initials: S
authors.lastname: Li
mesh_terms: D000641:Ammonia / Q000378:metabolism; D002072:Butylene Glycols / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007711:Klebsiella pneumoniae / Q000378:metabolism*; D011409:Propylene Glycols / Q000378:metabolism*
chemical_list: D002072:Butylene Glycols; D011409:Propylene Glycols; C026978:2,3-butylene glycol; C041787:1,3-propanediol; D000641:Ammonia; D005990:Glycerol