Chitinase from Bacillus sp. SRTI8: production, purification and biocontrol activities

From sand in the Algerian Sahara, an isolated strain of Bacillus called Bacillus sp. SRIT8 showed little chitinase activity when grown in a minimal medium supplemented with chitin (2.36 U). Using Plackett-Burman and Box-Behnken statistical plans, we could maximize chitinase synthesis, which led to a notable increase in this enzymatic activity (112 U). The purification of the resulting enzyme involved three steps: ammonium sulfate precipitation, molecular exclusion chromatography, and anion exchange chromatography. This process yielded a specific activity of 5437.14 U/mg with a purification yield of 22.44%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis examination revealed a protein band of about 31 kDa, and optimum enzyme activity was found at pH 5 and 40 °C. Enzyme activity was boosted by Ca+2, Na+, and Mn+2 ions but was suppressed by Hg+2 ions. The purified enzyme inhibited the growth of the plant pathogen Fusarium graminearum on wheat in both in vitro tests. So, it might prevent fungal infections in wheat throughout the germination process. The enzyme was also effective as a bioinsecticide, killing up to 52% of the larvae of Sitophilus granarius Linnaeus, an insect pest of stored grain. Our chitinase's capacity to hydrolyze fungus cell walls as well as insect cuticles can be utilised as biological control agent.