Efficient production of cellulolytic and xylanolytic enzymes by the rumen anaerobic fungus, Neocallimastix frontalis, in a repeated batch culture

In a batch culture of Neocallimastix frontalis in a medium (pH 6.8) contain ing 8 g.l(-1) cellulose, the concentrations of the fermentation products an d the cellulolytic and xylanolytic enzymes did not increase in comparison w ith those of cultures in a medium containing 4 g.l(-1) cellulose. Therefore , kinetic studies were performed to determine the effect that products such as acetate, formate, lactate and ethanol have in inhibiting the growth. Th e reduction of the specific growth rate by the fermentation products could be expressed by using a noncompetitive inhibition model, and it was found t hat at low concentrations, acetate was the strongest inhibitor among the in hibitory products studied. In order to reduce the inhibition by the ferment ation products, a repeated batch culture was carried out whereby none of th e fatty acids exceeded 50 mM. In this repeated batch culture, xylanase, end oglucanase, beta -glucosidase, and avicelase were continuously produced in the medium during cultivation, and 18200, 4550, 3790 and 129IU g.l(-1) of t hese enzymes, respectively, were produced up to 20 d of culture.