Effect of controlled substrate feeding on butyric acid production byClostridium tyrobutyricum

Production of butyric acid from wheat flour hydrolysate was studied withClostridium tyrobutyricum. The mode of substrate supply was found a key parameter for fermentation performance as large improvements were obtained by feeding with a non-limiting supply of substrate. With this procedure, increases in product concentration and productivity but also in selectivity and yield for butyrate were obtained. Substrate feeding controlled by the rate of gas production was found preferable to constant rate feeding for reason of convenience and flexibility. In these conditions, a butyrate concentration of 62.8 gl−1 was obtained with a productivity of 1.25 gl−1 h−1, a selectivity of 91.5% and a yield of 0.45 g per g of glucose.