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Process Development for Escherichia coli Based Pyruvate Production

The commercial demand for pyruvic acid has increased greatly in past decades owing to it various applications in the chemical and pharmaceutical industries, apart from the fact that pyruvate represents one of the most important metabolites in the central metabolism of the living cells. Pyruvic acid is produced on an industrial scale by the classical approach including dehydration and decarboxylation of tartaric acid in the presence of saturating amounts of potassium hydrogen sulfate followed by vacuum distillation. Although this process is simple to realize, it is not cost effective and does not fulfill demands for sustainable processes with low energy input. Therefore, different alternative biotechnological approaches for sustainable and environmental friendly pyruvate production have been developed. These process alternatives can be divided in the three different groups, enzymatic, resting cells and fermentation processes. Fermentation methods offer the opportunity to produce pyruvate from the sustainable low-cost substrate with high product/susbtrate yield, while avoiding the co production of unwanted byproducts. Pyruvate production process which use strain Escherichia coli YYC202 ldhA::Kan offers the best possibilities for downstream processing while it achieved in the same time the highest titers, pyruvate/glucose yield and volumetric productivities. This strain is completely blocked in its ability to convert pyruvate into acetyl-CoA or acetate, resulting in acetate auxotrophy during growth on minimal medium. Different process strategies, e.g. fed-batch, repetitive fed-batch, continuous with cell retention were developed and tested in order to optimized pyruvate production process. Experimentally observed inhibition by high pyruvate concentration in reaction mixture was overcome by development of in situ product recovery with fully integrated electrodialysis. Furthermore, modeling studies were performed to identify simple, easy-to-use and robust model that is suitable to support the engineering tasks of process optimization and design. Model which combined pyruvate inhibited growth and pyruvate inhibited product formation was identified as the best choice for description of bioconversion of glucose to pyruvate using genetically modified strain E. coli YYC202 ldhA::Kan. Results of the model simulation together with the experimental results were the base for the economical and ecological evaluation of the pyruvate production process. Process evaluation was performed using expected production process built in SuperPro Designer.

pyruvate, Escherichia coli, process development, modeling, economical and ecological evaluation

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