Among four isogenic catabolite repression-resistant Bacillus subtilis mutants grown on four different media, the strain crsA47 and the formula MII were chosen. Selection was supported by analyzing the results using the two-way Anova test. Supplementation of the medium with pectin resulted in a 1.33-fold increase in enzyme specific activity. A 2(n) factorial experiment was then applied to elucidate medium components that significantly affect enzyme formation. Significant factors were simultaneously optimized using the steepest ascent method. Optimized medium (tryptone, 10; yeast extract, 10; pectin, 2; and NaCl, 2 g l(-1)) yielded a crude filtrate with lichenase activity of 114 U ml(-1) and a specific activity of 20 U mg(-1) dry protein within 24 h of cultivation. Catabolite repression of lichenase synthesis was further limited by growing the crsA47 mutant on complex raw materials. The enzyme was maximally produced (123 U ml(-1), 38 U mg(-1) protein) by the cofermentation of cotton seed meal (36 g l(-1)) and lemon peel (9 g l(-1)).