A novel biopesticide production: attagel-mediated precipitation of chitinase from Beauveria bassiana SFB-205 supernatant for thermotolerance

Abstract

Insect killing fungi have high potential in controlling agriculturally harmful pest, but their slow progress and high variation in killing insect are major impediments to successful industrialization. The present work describes the use of supernatant from the liquid culture of Beauveria bassiana SFB-205 to surmount this problem, particularly efficient production of thermotolerant chitinase, which is one of the major pathogenesis-related enzymes in the supernatant. The chitinase was precipitated using varying mineral precipitants and followed by lyophilization, which was compared with a salting out method using ammonium sulfate in effectiveness. Incorporating of the supernatant fraction of the Beauveria preparation with attagel at 0.5% (w/v) as a precipitant enabled this treatment to show the greatest chitinase-precipitation efficiency (93.4%), followed up with excellent insecticidal activity against cotton aphids when it was mixed with 0.01% (v/v) polyoxyethylene-(3)-isotridecyl ether (TDE-3) as a spreading agent in laboratory conditions. Consequently, lyophilized attagel-mediated precipitation pellet was superior to lyophilized salting out pellet in maintaining chitinase activity against a thermal stress at 50 degrees C. This finding provides that the attagel-mediated precipitation can be exploited to improve the thermotolerance of B. bassiana SFB-205 chitinase as a novel strategy for biopesticide production.