engleski

Improvement of classical pyruvate production by novel Escherichia coli process

The commercial demand for pyruvic acid has increased greatly in past decades owing to it various applications, e. g. as an effective starting material for the synthesis of many drugs, agrochemicals and nowadays in food industry as a fat burner. In the recent work of our group, the fed-batch production of pyruvate using a recombinant Escherichia coli YYC202 ldhA::Kan strain was investigated [1, 2]. This strain is completely blocked in its ability to convert pyruvate into acetyl-CoA or acetate, therefore the strain requires aceatete for growth on glucose minimal medium. Glucose closed-loop control was established and acetate open-loop control was developed. Series of fed-batch processes were performed. At optimal process conditions final pyruvate titer higher than 700 mmol/L (62 g/L), integral molar yields of 1.10 mol pyruvate/mol glucose and a STY of 42 g/L/d were achieved. Evidence was obtained that high extra-cellular pyruvate concentration inhibits the process. To face this problem with process engineering means, repetitive fed-batch experiments with cell retention were performed. Molar yield pyruvate/glucose was improved up to 1.7 mol/mol. STY was increased more than 300 % and has reached 145 g/L/d. Continuous process with cell retention was developed to simplify complex set-up used for repetative fed-batch process. At optimal process conditions molar yield of 1.24 mol pyruvate/mol glucose and STY higher than 110 g/L/d were achieved. To separate pyruvate from fermentation broth fully integrated continuous process has been developed. In this process electro-dialysis was used as a separation unit. Under optimum conditions (calculated) final pyruvate titers higher than 900 mmol/L (79 g/L) were achieved. [1] Bott, M., Gerharz, T., Takors, R., Zelić, B., German Patent 10129714.4, 2001. [2] Gerharz, T., Zelić, B., Takors, R., Bott, M., German Patent 10220234.6, 2002.

E. coli; process development; pyruvate; electrodialysis

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