Enzymatic synthesis of L-aspartic acid by Escherichia coli cultured with a cost-effective corn plasm medium
2014
Zhao, Genhai | Gong, Guohong | Wang, Peng | Wang, Li | Liu, Hui | Zheng, Zhiming
This study was aimed at using corn plasm, an industrial by-product, as the main culture medium in the process of optimizing a genetically engineered Escherichia coli strain for the biosynthesis of aspartic acid. The significant effect of corn plasm, peptone, lactose, and incubation period on the activity of aspartase were noted with Plackett-Burman design and Box-Behnken design, which showed that peptone of 1.05 % (w/v), corn plasm of 8.23 % (w/v), lactose of 1.12 % (w/v), and an incubation period of 20.78 h were the optimal culture conditions. Under these conditions, the maximum predicted activity of aspartase was 3,985 U. The optimized conditions were verified by scale-up experiments, and the maximum activity of aspartase was recorded as 4,100.5 U. Adding trace metallic ions in optimized medium have an effect on the activity of aspartase. As compared with the basal medium, the initial reaction rate of aspartase increased by 2-fold, and the molar conversion rate increased to 1.5-fold. Substrate concentration (maximum of 3 M) and bioconversion temperature tolerance (maximum of 50 °C) also have obviously improved.
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