论文信息 - Control of carbon source supply and dissolved oxygen by use of carbon dioxide concentration of exhaust gas in fed-batch culture

Control of carbon source supply and dissolved oxygen by use of carbon dioxide concentration of exhaust gas in fed-batch culture

Accurate and automatic control strategies for a feedback-control system of volatile carbon source feeding and dissolved oxygen (DO) level were investigated. To maintain the optimal ethanol concentration for microbial growth, carbon dioxide concentration in exhaust gas was used as a stepwise control parameter of ethanol feeding. A proportional-differential (PD) control program was used to correct the errors. The coefficient of stepwise control was calculated stoichiometrically, and parameters of PD were experimentally preset and were not changed during cultivation. DO was also controlled by the PD control and the stepwise program based on carbon dioxide concentration of the exhaust gas. Agitation speed and partial pressure of oxygen of the inlet gas were changed stepwise in accordance with the oxygen consumption rate. The stepwise coefficients were estimated from stoichiometry and material balance of molecular oxygen. The PD control program was only used for the agitation speed control to correct the fluctuations of DO level. The parameters did not need to be changed during cultivation. By use of these sophisticated control programs for fed-batch culture of Candida brassicae, ethanol concentration and DO level were accurately controlled at 3.4–3.7 g/l and 2.2–2.8 ppm, respectively, while cell mass concentration reached about 80 g/l. No manual operation was needed.

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