Kinetic optimization of biodegradation and debromination of 2,4,6-tribromophenol using response surface methodology

2,4,6-Tribromophenol (2,4,6-TBP) is one of hazardous brominated flame retardants with acute toxicity which had an enormous applications in electronic devices and wood preservation. A bacterium Bacillus sp. GZT isolated in our lab was used to degrade 2,4,6-TBP and the response surface methodology was applied to optimize the biodegradation and debromination kinetics of 2,4,6-TBP. The central composite design model was chose to mathematically describe those affecting parameters of biodegradation. Three factors were determined to be the function of parameters, such as 2,4,6-TBP concentration (X1), initial pH value (X2) and the inoculum volume (X3). The results showed that two responses, degradation efficiency (%) (Y1) and debromination efficiency (%) (Y2), were coincidently affected by significant factors of the linear terms of x2 and x3 with synergistic effect, but quadratic terms of x22 and x32 with antagonistic effect, and linear terms of x1 also had antagonistic effect on those two responses. The optimal conditions for Y1 and Y2 were 3.0 mg/L 2,4,6-TBP with 20.7 ml inoculum volume at pH value 7.3, and the estimated maximum responses were 94.6% and 88.6%, respectively. The experimental values were agreed with the theoretical results very well, indicating that the models employed to optimize the biodegradation and debromination of 2,4,6-TBP were effective.