Optimized cellulase production by Phanerochaete chrysosporium: control of catabolite repression by fed-batch cultivation

Abstract

The cellulase system of Phanerochaete chrysosporium is adaptive and thus sensitive to carbon catabolite repression. Our attempts to optimize cellulase production have led to significant improvements. Specific yields (cellulase produced per carbon source) in batch cultivations on cellulose were of the order of 40–60 mg/g. In fed-batch cultivation, however, specific yield was improved to 120 mg/g when cellulose was the substrate. Using cellobiose as the substrate a yield of 100–130 mg/g was routinely obtained. The effectiveness of the technique is clearly shown by the result obtained in a cultivation where cellobiose and glucose were fed simultaneously. Although the cellobiose added represents about 50% of the glucose added, the specific yield achieved, 70 mg/g, was still higher than in batch cultivations on cellulose. However, the cellulase production rate in this culture was very sensitive to changes in culture conditions. The protein, the avicelase-and the CMCase-activity profiles produced on either pure or mixed carbon sources were very similar.