Optimization of protease production by Microbacterium sp. in feather meal using response surface methodology

A 23 factorial design was performed with the aim of optimizing protease production by a strain of Microbacterium sp. isolated from feathers in decomposition by response surface methodology. Protease production was first tested on different nitrogen source (casein, peptone, yeast extract, gelatin, soybean protein, feather meal and cheese whey). Feather meal was the selected substrate to test the effect of three variables on protease production (temperature, initial pH and feather meal concentration) by RSM. The point was chosen with these conditions: temperature 37 °C, initial pH 7.0 and feather meal concentration 12.5 g l−1. Statistical analysis of results showed that, in the range studied, only pH did not have a significant effect on protease production whereas interaction between pH and feather meal concentration was significant. The optimum conditions were 25 °C, initial pH 7.0 and 12.5 g l−1 of feather meal. Under these conditions, the model predicted a protease activity of 202.7 U ml−1.