B. Zelić, Đ. Vasić-Rački: Recovery of pyruvic acid from fermentation broth: process development and modeling RECOVERY OF PYRUVIC ACID FROM FERMENTATION BROTH: PROCESS DEVELOPMENT AND MODELING

Besides the production process, the product recovery must be also taken into consideration – not only because of its usually high contribution to the total process costs but also on account of the necessity of integrating it on-line into the production process if the product is inhibitory. In the case of pyruvate, some indications have been published that high extra-cellular pyruvate concentrations > 500 mmol dm might cause a significant inhibition of microbial pyruvate synthesis. Hence, pyruvate process development should consider strategies for the separation of the product and to purify it as well. Ion exchange and solvent extraction followed by distillation are common methods for pyruvate separation from cell-free fermentation broth. However, the low exchange capacity of resins and the use of concentrated acids as eluents makes the application of ion-exchange for pyruvate isolation very difficult and not attractive in terms of sustainable process development as well as in commercial retrospect. However, the charge-dependent ion-separation in the electric field of electrodialysis is regarded as a promising approach for the downstream processing of organic acids from fermentation broth. It has been widely applied for production of table salts, organic acids, amino acids and sugar demineralization as well as for blood treatment and wine stabilization. Electrodialysis represents one of the most important membrane processes for environmentally clean technology in biochemical industries. To develop a pyruvate production process with integrated product separation using the production strain Escherichia coli YYC202 ldhA::Kan, was motivated by the working hypothesis that high extra cellular pyruvate concentrations might be inhibitory. To separate pyruvate from fermentation broth a fully integrated continuous process has been developed. In this process electrodialysis was used as a separation unit. Additionally, mathematical model to represent the ion and water transport behavior of an electrodialysis process for concentrating pyruvic acid under the influence of different current density was developed. The model validation will be demonstrated in the work.