Optimization of medium composition for protease production by Paecilomyces marquandii in solid-state- fermentation using response surface methodology

The present work was aimed to evaluate the optimization of medium composition for protease production by Paecilomyces marquandii in solid-state-fermentation using response surface methodology. Wheat bran was used as substrate for protease production. The variables tested were as follows: pH, tryptone and days of incubation. The proteolytic activity was measured by caseinolytic method. The Central Composite Design (CCD) was applied to determine the optimal concentration of the tested significant variables. A full factorial central composite experimental was used with six replicates at the central point. A total of 20 experiments were used to investigate the variables. The best fermentation conditions found after optimization were pH 5.0, tryptone 0.02 g/l and 5 days of incubation which yielded about 118 U/ml. The enzyme production of submerged fermentation (46 U/ml) was 2.57 times lower than the highest enzyme production of solid state fermentation (118 U/ml). The results indicate that pH, tryptone and days of incubation optimized the production of proteases by fungus P. marquandii in solid state fermentation.This is the first work about optimizing the production of proteases in solid state fermentation by the fungus P. marquandii.   Key words: Solid state fermentation, Paecilomyces marquandii, protease, optimization, response surface.