Verlag des Forschungszentrums Jülich
JUEL-4100
Key words : process development, Escherichia coli, pyruvate, modeling, in situ product
recovery
Zelic, Bruno
Study of the Process Development for Escherichia coli Based Pyruvate Production
119 S., 2003
The commercial demand for pyruvic acid has increased greatly in past decades owing
to it varions applications, e. g. as an effective starting material for the synthesis of many
drugs, agrochemicals and nowadays in food industry as a fat burner. The main goal in this
project was the development of a pyruvate production process from glucose with a high molar
pyruvate/glucose yield (approaching 2 mol pyruvate/mol glucose) and space-time yield using
a recombinant Escherichia coli YYC202 strain. This strain is completely blocked in its ability
to convert pyruvate in acetyl-CoA or acetate, resulting in acetate-auxotrophy during growth in
glucose minimal medium.
Due to the strain genotype, acetate availability was assumed to represent a key
fermentation variable. Experimental studies identified a "simple" correlation between acetate
consumption rate (ACR) and C02 production rate (CTR) with an optimum equal molar ratio .
Therefore, CTR (calculated on-line by C02 and 02 exhaust gas analysis) was used for on-line
calculation and regulation of the acetate feed (acetate limiting, saturating and accumulating
conditions could be established) . Glucose closed-loop control was established and series of
fed-batch processes were performed. At optimal process conditions final pyruvate titer higher
than 700 mmol dm -3 (62 g dm-3), integral molar yields of 1.11 mol pyruvate/mol glucose and
a space time yield (STY) of 42 g dm-3 d-1 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-1 . STY was increased more than 300 % and has reached 145 g dm-3 d-1 . Continuous
process with cell retention was developed to simplify complex set-up used for repetative fedbatch
process. At optimal process conditions molar yield of 1 .24 mol pyruvate/mol glucose
and STY higher than 110 g dm-3 d-1 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 final (calculated) pyruvate titers higher than 900 mmol dm-3 (79 g dm-3) were
achieved. Additionally, unstructured models for the bioconversion of glucose to pyruvate, as
well as a model of the electrodialysis process were developed, process parameters were
estimated and both models were validated.
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