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

Abstract

Liquid cultivation for the production of mycoinsecticides has received recent attention by the industry, 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 dissolved 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 experimental 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 composite rotational design (CCRD). The optimized conditions resulted in high concentrations of submerged spores (2.21 × 109 SS mL−1) and colony forming units (1.52 × 109 CFU mL−1) on the third day of cultivation. There was an increase of 165.05% and 210.16% in SS and CFU production, 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 provided the highest concentrations of SS (1.98 × 109 SS mL−1) and CFU (1.9 × 109 CFU mL−1) after four days of growth.