The reaction conditions were optimized for enzymatic hydrolysis of pectic substances using pectolytic enzymes produced by Aspergillus niger NCIM 548. Response surface methodology was used to optimize the reaction parameters and the central composite design was employed for this purpose. Pectin was used as the substrate for polymethylgalacturonase and pectinlyase, whereas polygalacturonic acid was the substrate for polygalacturonase. The volume ratio of reactants for maximum hydrolysis was determined under the assay conditions. The optimum amount of substrate and enzyme were found to be 0.2 cm3 and 0.074 cm3 for polymethylgalacturonase, 0.4 cm3 and 0.086 cm3 for polygalacturonase, and 0.63 cm3 and 0.7 cm3 for pectinlyase. The pH and temperature optima were found to be 5.3 and 30°C for polymethylgalacturonase, 6.6 and 26°C for polygalacturonase, and 4.8 and 35°C for pectinlyase. Under optimized conditions the enzyme activities were higher when compared to unoptimized conditions. Copyright (C) 1999 Elsevier Science Inc.The reaction conditions were optimized for enzymatic hydrolysis of pectic substances using pectolytic enzymes produced by Aspergillus niger NCIM 548. Response surface methodology was used to optimize the reaction parameters and the central composite design was employed for this purpose. Pectin was used as the substrate for polymethylgalacturonase and pectinlyase, whereas polygalacturonic acid was the substrate for polygalacturonase. The volume ratio of reactants for maximum hydrolysis was determined under the assay conditions. The optimum amount of substrate and enzyme were found to be 0.2 cm3 and 0.074 cm3 for polymethylgalacturonase, 0.4 cm3 and 0.086 cm3 for polygalacturonase, and 0.63 cm3 and 0.7 cm3 for pectinlyase. The pH and temperature optima were found to be 5.3 and 30°C for polymethylgalacturonase, 6.6 and 26°C for polygalacturonase, and 4.8 and 35°C for pectinlyase. Under optimized conditions the enzyme activities were higher when compared to unoptimized conditions.