Debaryomyces nepalensis was previously isolated, which is capable of producing pectin lyase and pectate lyase using pectin as sole source of carbon. The parameters affecting the activity of these enzymes are categorized into two, viz., chemical (amount of substrate and enzyme) and physical (pH of reaction mixture and temperature of incubation). The effect of these parameters on pectin lyase and pectate lyase was studied using central composite design. The optimal conditions of amount of substrate and enzyme (culture broth) were found to be 545 μl (∼1 g/l pectin) and 123 μl for pectin lyase and 707 μl (∼1.1 g/l polygalacturonic acid) and 96 μl for pectate lyase. The optimum pH and temperature for reaction was found to be 6.4 and 35 °C for pectin lyase and 7.5 and 32 °C for pectate lyase. After optimization, the activity of pectin lyase and pectate lyase was increased by 1.3- and 1.4-fold, respectively. © 2006 Elsevier B.V. All rights reserved.