Effect of temperature on synthesis of clavulanic acid and impurity substance G during fermentation by Streptomyces clavuligerus

Effect of temperature on synthesis of Clavulanic acid (CA) and impurity substance G during fermentation by Streptomyces clavuligerus were investigated. Results show that fermentation at 24 °C is the most favorable for CA synthesis though the fermentation duration was 20–30 hours longer than fermentation at 26 and 28 °C. Meanwhile, the impurity substance G was only 110 mg/L in the end broth of fermentation at 24 °C, which was significantly lower than 148 and 180 mg/L of fermentation at 26 and 28 °C, respectively. Correlation of specific growth rate and CA synthesis was statistically analyzed based on data of 10 batches of industrial fermentation. Two temperature-shift strategies were investigated in 50 L fermenter. Fermentation with 26–24 °C temperature strategy achieved 5097 mg/L CA titer, meanwhile the fermentation duration was shortened 24 hours comparing with fermentation at constant 24 °C. Fermentation with 26–24 °C control strategy was validated in a 60 m3 industrial fermenter, in which 4960 mg/L of CA was achieved while impurity G substance was decreased to titer 65 mg/L from 200 to 300 mg/L of normal production.