Optimization of bilirubin oxidase production conditions by Myrothecium sp.IMER1under solid fermentation using response surface methodology

To improve bilirubin oxidase production by Myrothecium sp.IMER1, the fermentation conditions of bilirubin oxidase (BOX) production by Myrothecium sp.IMER1 under solid fermentation were optimized by response surface methodology. Based on pre-test results, Plackett-Burman design was used to evaluate the effects of five factors related to BOX production and three statistically significant factors moisture content, pH and temperature were selected. The path of steepest ascent was used to approach the optimal region of BOX production subsequently. Then, the optimal combined concentration for maximum enzyme activity were further optimized by response surface methodology and determined as follows: 4.6, 23°C and 83.5%. The optimization of culture conditions of IMER1 led to about 2 fold increases in BOX production compared to the initial, which indicate that single factor in combination with response surface methodology is an effective method for optimization of BOX production conditions by Myrotheciumsp.IMER1. The maximum amount of enzyme under solid fermentation is found on the fifth day, but high BOX yield can be sustained; Its extracellular enzyme activity were analyzed by native electrophoresis, the results show that BOX can be detected and no BOX isozymes appear.