Pectinases are a group of enzymes that are responsible for degredation of pectic substances. Pectinases are produced by many organisms including plants, bacteria and fungi. The aim of this study was to investigate the effect of different carbon sources and pH on pectinase production by a group of flamentous fungi. For this purpose, Aspergillus niger, Rhizopus oryzae ATCC 4858, Aspergillus sojae ATCC 2035 (A. sojae WT) and its mutant type Aspegillus sojae MT (A. sojae MT) grown in orange peel containing media were evaluated in terms of exo-polygalacturonase (exo-PG), pectin lyase (PL), pectin methyl esterase (PME), and also xylanase and cellulase activities. A. sojae WT and A. sojae MT were found to be as exo-PG producers. Maximum exo-PG activities were 47.84 U/ml and 108.02 U/ml, respectively. Exo-PG production by A. sojae WT and A. sojae MT was evaluated using the medium containing glucose, pectin, pectin/glucose, pectin/fructose and pectin/sucrose as substrate. Additional supply of glucose to the pectin media was found to be more effective than fructose or sucrose. The fermentations in which pH was not maintained, the use of glucose, pectin and pectin/glucose resulted in superior enzyme activities compared to ones obtained with other media compositions.