The synthesis of pectolytic enzymes appears to be considerably influenced by the glucose content of the cultivation medium containing mixed carbon sources in a predetermined optimal ratio. Glucose is an essential component in the fermentation, promoting cell growth while the synthesis of pectolytic enzymes was found to be induced by the second carbon source, corn, only when the glucose concentration in the medium was significantly low. Studies conducted to examine the effect of glucose showed that glucose severely reduced the synthesis of polygalacturonase and polymethylgalacturonase at concentrations above 5g/l while pectinlyase was unaffected. In vitro studies showed that the inhibition of the two pectin hydrolases was reversible and competitive in nature. The results of the study also indicate induction of pectolytic enzymes by corn in Aspergillus niger NCIM 548. © 2004 Elsevier Inc. All rights reserved.