Abstract

Sequences of experimental designs were applied to optimize medium and fermentation conditions in order to enhance the tyrothricin production by Bacillus brevis (ATCC 8185). A significant influence of casein peptone, NaCl and yeast extract on tyrothricin yield was evaluated by Plackett–Burman (PB) design. The optimal concentration range of the three factors was examined by the steepest ascent method and the medium formulation was optimized by the central compose design (CCD) and response surface methodology (RSM). Under the optimal conditions, the concentrations of the selected factors were found as 10.28 g/L casein peptone, 4.62 g/L NaCl and 11.03 g/L yeast extract. Tyrothricin production obtained was in agreement with the predicted value and the model was proven to be adequate. Within the optimization procedure, the enhancement of tyrothricin from 116.14 to 594.50 μg/ml was achieved.

Key words: Tyrothricin, Bacillus brevis, optimization, response surface methodology.

Abbreviation

 CCD, Central composite design; RSM, response surface methodology; PB, Plackett-Burman