LOGICAL AND EXPERIMENTAL DESIGN FOR PHENOL DEGRADATION USING IMMOBILIZED ACINETOBACTER SP. CULTURE

Abstract

Phenol degradation processes were conducted through a series of enzymatic reactions effects and is affect by different components of the microbial metabolic flux. Using different optimization strategies like mutagenesis could lead to a successful optimization but also lead to lost of some important microbial features or to release a new virulence or unexpected characters. Plackett-Burman closes much gab between optimization, safety, time, cost, Man/hr, the complexity of the metabolic flux etc. Using Plackett-Burman experimental design lead to map the points affect in the optimization process by well understanding their request from nutrient and the best environmental condition required. In this study nine variables include pH (X1), oC (X2), glucose (X3), yeast extract (X4), meat extract (X5), NH4NO3 (X6), K-salt (X7), Mg-salt (X8) and trace element (X9) are optimized during phenol degradation by Acinetobacter sp., using Plackett-Burman design method. Plackett-Burman included 16 experiments, each was used in two levels, [-1] low and high [+1]. According to Blackett-Burman design experiments the maximum degradation rate was 31.25 mg/l/h. Logical and statistical analysis of the data lead to select pH, Temperature and Meat extract as three factors affecting on phenol degradation rate. These three variables have been used in Box-Behnken experimental design for further optimization. Meat extract, which is not statistically recommended for optimization has been used while it can substitute trace element, which is statistically significant. Glucose, which is statistically significant, did not included while it has a negative effect and gave the best result at 0 g/l amount. Glucose has been completely omitted from the media.  pH, temperature and meat extract were used in fifteen experiments each was used in three levels, –1, 0, and +1 according to Box-Behnken design. Microsoft Excel 2002 solver tool was used to optimize the model created from Box-Behnken. The calculated degradation rate was 37.30 mg/l/hr at pH=7.12, Meat extract=1.6 g/l and Temperature=27.77oC. To prove the efficiency of using the Microsoft Excel 2000 solver the calculated variables are tested experimentally in vivo. The degradation rate was 38.45 mg/L/hr, which equal to 103.08% accuracy. The high accuracy level points out the efficiency of using Box-Behnken experimental design and the Excel solver to optimize its model.