Optimization and Modeling of Citrobacter freundii AD119 Growth and 1,3-Propanediol Production Using Two-Step Statistical Experimental Design and Artificial Neural Networks

1,3-propanediol (1,3-PD) has a wide range of industrial applications. The most studied natural producers capable of fermenting glycerol to 1,3-PD belong to the genera Klebsiella, Citrobacter, and Clostridium. In this study, the optimization of medium composition for the biosynthesis of 1,3-PD by Citrobacter freundii AD119 was performed using the one-factor-at-a-time method (OFAT) and a two-step statistical experimental design. Eleven mineral components were tested for their impact on the process using the Plackett-Burman design. MgSO4 and CoCl2 were found to have the most pronounced effect. Consequently, a central composite design was used to optimize the concentration of these mineral components. Besides minerals, carbon and nitrogen sources were also optimized. Partial glycerol substitution with other carbon sources was found not to improve the bioconversion process. Moreover, although yeast extract was found to be the best nitrogen source, it was possible to replace it in part with (NH4)(2)SO4 without a negative impact on 1,3-PD production. As a part of the optimization procedure, an artificial neural network model of the growth of C. freundii and 1,3-PD production was developed as a predictive tool supporting the design and control of the bioprocess under study.

Automated summary

In this study, the medium composition for the biosynthesis of 1,3-propanediol by Citrobacter freundii AD119 was optimized using the one-factor-at-a-time method and a two-step statistical experimental design. The impact of eleven mineral components was tested, and it was found that MgSO4 and CoCl2 had the most pronounced effect. Carbon and nitrogen sources were also optimized, and it was determined that partial glycerol substitution with other carbon sources did not improve the bioconversion process. Furthermore, a predictive neural network model of C. freundii growth and 1,3-propanediol production was developed to support the design and control of the bioprocess.