Screening and combination of efficient desulfurizing-bacteria and toluene degrading bacteria and degradation condition optimization of mixed bacteria

The paper reports the domestication, screening and combination of the toluene degrading bacteria and desulfurizing-bacteria, investigates the degradation conditions of mixed bacteria, with sodium thiosulfate and toluene as substrate, respectively. Four strains of efficient desulfurizing-bacteria (Z₁, Z₂, Z₃, and B₁) and three strains of toluene degradation bacteria (J₁, J₂, and J₃) were obtained by domesticating bacteria sources. Then, the two kinds of strains were combined to obtain the best combination mode for (Z₁+Z₂)-B₁- (J₁+J₃), and the density ratio of thallus 2:4:3. In addition, The central composite design (CCD) of response surface method (RSM) was used for optimizing the degradation condition of the mixed bacteria, SO₄^2- concentration and toluene degradation rate as control index. The optimum conditions were as follows: pH 6.8, temperature 30.0°C, inoculation amount 3.0%, toluene mass 3.0 μL/80 mL, and sodium thiosulfate mass 4.4 g/L.The verified experiment shows that toluene degradation rate can reach 73.9% and SO₄^2- concentration of 163.9 mg/L under the best degradation conditions, which was basically identical to the prediction results, and improved significantly compared with removal performance before optimization.