High concentration of spores and colony forming units of the biocontrol agent Beauveria bassiana via optimization of submerged cultivation

Liquid cultivation for the production of mycoinsecticides has received recent attention by the in-dustry, due to the many advantages over the solid-state cultivation process. However, important variables must be considered to enable the production of the fungus propagules in the liquid medium. In this study, the optimization of the culture medium and the influence of pH and dis-solved oxygen (DO) parameters on the production of spores of Beauveria bassiana in liquid process was investigated. The strain of B. bassiana IBCB 868 was growth in shake flasks followed by ex-perimental design to find the optimal medium condition for spores production. Optimization of the culture medium was performed using a Plackett-Burman design followed by a central com-posite rotational design (CCRD). The optimized conditions resulted in high concentrations of sub-merged spores (2.21 x 109 SS mL-1) and colony forming units (1.52 x 109 CFU mL-1) on the third day of cultivation. There was an increase of 165.05% and 210.16% in SS and CFU produc-tion, respectively, in the optimized condition when compared to the most favorable culture medium initially tested. Benchtop bioreactor assays with the optimized medium were performed and the influence of pH and DO was investigated. It was observed that the pH fixed at 4.5 and 10% DO in 24 h, followed by 50% DO until 48 h and 30% DO until the end of the cultivation pro-vided the highest concentrations of SS (1.98 x 109 SS mL-1) and CFU (1.9 x 109 CFU mL-1) af-ter four days of growth.