Repeated fed-batch lactic acid production in a packed bed-stirred fermentor system using a pH feedback feeding method

摘要

Lactic acid production by repeated fed-batch fermentation using free and immobilized cells of Lacto-bacillus lactis-11 in a packed bed-stirred fermentor (PBSF) system filled with different support materials including ceramic beads, macro-activated carbon cylinders and glass fiber balls was investigated. The results showed that the optimal support materials were the ceramic beads with diameters of 1-2 mm. Compared with the free cell fermentation system, lactic acid production and volumetric productivity in the PBSF system increased by 16.6 and 12.5%, respectively. Though the concentration of free cells decreased sharply, lactic acid production remained stable in five consecutive fed-batch runs using the PBSF system. pH gradients, immobilized cell concentration and mass diffusion in the packed bed were all affected by the recir-culation rate of the culture broth. Maximum lactic acid production, productivity and yield occurred at a recircula-tion rate of 50 mL min~(-1).