“…In order to alleviate the osmotic stress inhibition in organic acid fermentations and to further increase the yield and productivity of organic acid, a lot of metabolic and process engineering techniques have been developed (Roffler, 1984). The process engineering strategies mainly involved with the in situ product removal systems, such as precipitation, solvent extraction (Schügerl, 1994), ion exchange (Vaccari et al, 1993), ultrafiltration membranes, electrodialysis (Bruno et al, 2004;Nomura et al, 1987), and crystallization (Takamatsu and Ryu, 1988). For example, in order to enhance the pyruvate production by E. coli, a fully integrated continuous process with electro-dialysis was developed to separate pyruvate from fermentation broth, so that a high pyruvate concentration of 79 g/L was achieved (Bruno et al, 2004).…”