Response surface optimization of conditions for culturing Azotobacter chroococcum in Agaricus bisporus industrial wastewater.

In the present study, the conditions for Azotobacter chroococcum fermentation using Agaricus bisporus wastewater as the culture medium were optimized. We analyzed the total number of living A. chroococcum in the fermentation broth, using multispectral imaging flow cytometry. Single-factor experiments were carried out, where a Plackett-Burman design was used to screen out three factors from the original six processing factors wastewater solubility, initial pH, inoculum size, liquid volume, culture temperature, and rotation speed that affected the total number of viable A. chroococcum. The Box-Behnken response surface method was used to optimize the interactions between the three main factors and to predict the optimal fermentation conditions. Factors significantly affecting the total number of viable A. chroococcum, including rotation speed, wastewater solubility, and culture temperature, were investigated. The optimum conditions for A. chroococcum fermentation in A. bisporus wastewater were a rotation speed of 200 rpm, a solubility of 0.25%, a culture temperature of 26°C, an initial pH of 6.8, a 5% inoculation volume, a culture time of 48 h, and a liquid volume of 120 mL in a 250 mL flask. Under these conditions, the concentration of total viable bacteria reached 4.29 ± 0.02 ✕ 107 Obj/mL A. bisporus wastewater can be used for the cultivation of A. chroococcum.