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Fed-Batch Kinetics and Modeling Of Schizochytrium Sp. FJU-512 Growth and DHA Production in Fermentations Using a Shift Control Strategy

Mingliang Zhang, Feng Qi, Xianzhang Jiang, You Weichen, Weibin Wu, Xiaolei Guo and Jianzhong Huang

A set of kinetic models were established for the fed-batch production of DHA by Schizochytrium sp. FJU-512 in 151 and 1001 fermenters using a strategy that applies nitrogen stress in combination with shifts of DO concentration and temperature. A compensatory parameter n was integrated into the model in order to find the optimal mathematical equations. A modified Logistic model was proposed to fit the cell growth data, and the following kinetic parameters were obtained: μ_m=0.0525 h^-1, X_m=100 g l^-1 and n=4.1717 for the 151 bioreactor, as well as μ_m=0.0382 h^-1, X_m=107.4371 g l^-1 and n=10 for the 1001 bioreactor. The Luedeking-Piret equations were utilized to model DHA production, yielding values of α=0.0648 g.g^-1 and β=0.0014 g.g^-1.h^-1 for the 151 bioreactor, while the values of α and β obtained for the 1001 fermentation were 0.0209 g.g^-1 and 0.0030 g.g^-1.h^-1. The established models had a good fitting precision and were able to exactly depict the dynamic features of the DHA production process which utilizes Schizochytrium sp. FJU-512.