Response surface methodology for the optimization of keratinase production in culture medium containing feathers produced by Kocuria rosea.

A 43-fold increase in keratinase production by Kocuria rosea was achieved in batch fermentation using response surface methodology. Factorial designs were used to select the components of a culture medium that showed a significant effect on keratinase production. An orthogonal-central composite experimental design was performed, with only two (feathers and magnesium) from nine initial compounds being further analyzed by response surface methodology. An optimum keratinase production of 14 886.9 U/mg was obtained with the following medium composition (per litre): NH4Cl, 0.3 g; NaCl, 0.3 g; K2HPO4, 3.2 g; KH2PO4, 4.0 g; MgSO4.6H2O, 0.5 g; yeast extract, 0.1 g; and finely milled feathers, 30 g. The medium was shaken at 400 r/min with an incubation period of 14 h at 40 degrees C.