Biocontrol potential of Vibrio maritimus chitinase: Heterologous expression and insecticidal activity against Acanthoscelides obtectus

Abstract

In this study, the chitinase gene from the marine bacterium Vibrio maritimus was heterologously expressed in Escherichia coli, purified via affinity chromatography and tested for its insecticidal activity against the storage pest Acanthoscelides obtectus. The recombinant VmChiA protein exhibited a molecular mass of ∼60 kDa, with optimum activity observed at pH 6.0 and 40 °C. Enzyme kinetic analysis revealed a K_m value of 0.042 mM, V_max of 17.48 μmol min⁻¹, k_cat of 1.75 min⁻¹ and catalytic efficiency of 41.61 mM⁻¹ min⁻¹, respectively. Furthermore, a dose of 40 U mL⁻¹ of recombinant VmChiA showed similar efficacy to malathion insecticide against A. obtectus, with 100 % mortality in both treatments. LC₅₀ and LC₉₀ values of VmChiA were 13.95 U mL⁻¹ and 27.66 U mL⁻¹, respectively. Furthermore, the three-dimensional structure of the catalytic site of VmChiA was modeled. Molecular dynamics simulation technique was used to explore and analyze the dynamics and interactions. A salt bridge (GLU274-ARG296) in the α + β domain was observed as a critical feature facilitating substrate (GlcNAc)₂ binding and enzymatic activity. These findings demonstrate that recombinant VmChiA possesses potent insecticidal properties, highlighting its potential as a bio-based, eco-friendly alternative for managing significant agricultural pests.