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Kinetics-based development of two-stage continuous fermentation of 1,3-propanediol from glycerol by Clostridium butyricum
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  • Zhi-Long Xiu,
  • Xiao-Li Wang,
  • yaqin sun,
  • Duo-Tao Pan
Zhi-Long Xiu
Dalian University of Technology School of Bioengineering

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Xiao-Li Wang
Dalian University of Technology School of Bioengineering
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yaqin sun
Dalian University of Technology School of Bioengineering
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Duo-Tao Pan
Shenyang University of Chemical Technology
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Abstract

Continuous fermentation has many striking merits over fed-batch and batch fermentation, such as easy operation and long-term high productivity without frequent seed culture and energy-intensive sterilization. However, it is usually difficult to harvest high product concentrations. In this study, a three-stage continuous fermentation was firstly designed to produce 1,3-propanediol (1,3-PDO) from crude glycerol by Clostridium butyricum, in which the first stage fermentation was responsible for providing the excellent cells in a robust growth state, the second stage focused on promoting 1,3-PDO production, and the third stage aimed to further boost the 1,3-PDO concentration and reduce the residual glycerol concentration as much as possible. Through the three-stage continuous fermentation, 80.05 g/L 1,3-PDO as the maximum concentration was produced while maintaining residual glycerol of 5.87 g/L, achieving a yield of 0.48 g/g and a productivity of 3.67 g/(L·h). Based on the 14 sets of experimental data from the first stage, a kinetic model was developed to describe the intricate relationships among the concentrations of 1,3-PDO, substrate, biomass and butyrate. Subsequently, this kinetic model was used to optimize and predict the highest 1,3-PDO productivity of 11.26 g/(L·h) in the first stage fermentation, while the glycerol feeding concentration and dilution rate were determined to be 92 g/L and 0.34 h -1, separately. Additionally, to achieve a target 1,3-PDO production of 80 g/L without the third stage fermentation, the predicted minimum volume ratio of the second fermenter to the first one was 11.9. The kinetics-based two-stage continuous fermentation was experimentally verified well with the predicted results. This kinetics-based development of continuous fermentation provides an effective tool for other bio-chemicals production by continuous fermentation.