S162: Fed-batch process of rapamycin fermentation with DCO2 on-line measurement

A Streptomyces fed-batch fermentation was studied with on-line measurement of dissolved carbon dioxide (DCO₂). A selected cell strain of Streptomyces hygroscopicus was used in the production of rapamycin. pH was controlled only in the production phase at the low limit of 5.1. DCO₂ was used to control the feed. The experiment investigated the relationship between rapamycin production and the evolution of DCO₂. A controlled high limit of DCO₂ (hDCO₂) was used to control medium feed. In order to meet the needs for the dynamic growth and metabolism of cells in the process, the hDCO₂ was defined as a dynamic parameter, and was therefore calculated constantly in the process. A fermentation condition of limited nutrient supply was realized to optimize the production of its secondary metabolite. It was observed that rapamycin was secreted when the glycerol concentration was well controlled in the fermentation condition. Experimental results showed that 550 mg/l of rapamycin was produced in 140 h of fermentation.