Applying Factorial Design and Response Surface Methodology to Enhance Microbial Denitrogenation by Tween 80 and Yeast Extract

Abstract

In this study the effect of yeast extract as a conitrogen source and Tween 80 as a commercial and available nonionic surfactant on microbial denitrogenation MDN of carbazole by Bacillus clausii BS1 was investigated. The central composite design matrix and response surface methodology were applied in designing the batch experiments to evaluate the interactive effects of these two parameters on MDN. Quadratic model equations have been predicted finding out how significant the effects of these variables (factors) and their interactions are in practice. The validity of the predicted models was confirmed. The MDN efficiency increased from ≈88% without yeast extract or Tween 80 to ≈95% in presence of optimum concentration of 0.868 g/L yeast extract and 0.861% (v:v) Tween 80, which would represent a major economic improvement in low-margin, high-volume refining processes.