[Optimization of culture conditions for Clostridium cellulolyticum]

Clostridium cellulolyticum, as one of obligate anaerobic bacteria capable of secreting cellulosome, has not been efficiently cultured due to its strict requirement of growing conditions. In this study, culture conditions of C. cellulolyticum were optimized using response surface methodology. Plackett-Burman design was first used to screen the dominant impact factors for the growth of C. cellulolyticum, which were determined as yeast extract concentration, cellobiose concentration and culture temperature. The steepest ascent path design was then applied to gain the suitable range close to the optimal culture conditions for obtaining high cell density. The central composite design and the response surface analysis were finally used to determine the optimal levels of the influential factors, which were 3 g/L for yeast extract concentration, 7 g/L cellobiose concentration and 34 degrees C for culture temperature. The optimized medium was used for flask culture, and OD600 of C. cellulolyticum was increased from 0.303 to 0.586. With a pH-controlled fermentor at batch mode, OD600 reached 3.432, which was 2.8 times higher than elsewhere reported. These results support further study on the high-density culture of C. cellulolyticum and its application.