Screening for Aspergillus fumigatus strain-2T-2 with high chitosanase production activity and its application in chitosan degradation

Background High chitosanase producing microorganisms from natural sources have extensive applications in food and agriculture. This study aimed to optimal conditions for high activity chitosanase production. A named CGMCC21422 chitosanase-producing strain -2T-2 was isolated from soil and identified named as Aspergillus fumigatus chitosanase (A. fumigatus chitosanase). This enzymatic activity was validated in various culture conditions. It is stored in the China General Microbiological Culture Collection Center. The efficacy of A. fumigatus chitosanase in degradation of chitosan was validated. Results In this study, we determined that the optimal fermentation conditions of stain-2T-2 was 1.0% powered chitosan, 0.8% ammonium nitrate, 37°C culture temperature, initial pH 5.0, culture time 6 d, bottle volume 50 mL, and 2% inoculation dosage. Under these culture conditions, the highest enzyme activity of fermentation broth in the shaker flask reached 827.53 U/mL. The optimal reactive conditions of A. fumigatus produced chitosanase are 55-60°C and pH 4.5. When reactive temperature was over 60°C, the A. fumigatus chitosanase was easily inactivated. The chitosanase catalyzed substrate chitosan to produced ≈20% chito-oligosaccharide and ≥80% glucosamine salt samples in a variety of acidic solutions. These reactive products are not cytotoxic or mild to MH7A cells. Conclusions A. fumigatus chitosanase strain -2T-2 is a strain with high chitosanase and can catalyze chitosan into chito-oligosaccharide in acidic solutions.