Identification and Nematicidal Characterization of an Extracellular Chitinase BLChi79 from Brevibacillus laterosporus Strain XJ-24-3

This study aimed to identify and characterize a high-efficiency chitinase gene from Brevibacillus laterosporus (B. laterosporus), characterize its enzymatic traits, and assess its degrading activity against Caenorhabditis elegans (C. elegans) and Parascaris equorum (P. equorum) eggs. A nematicidal B. laterosporus isolate was subjected to whole-genome sequencing for chitinase gene screening, cloning, and molecular identification. The target gene was heterologously expressed in Escherichia coli BL21 (DE3), and biochemical properties including temperature, pH, metal ions, and substrate conditions were investigated, its kinetic parameters were determined, and its biological effects on C. elegans and P. equorum eggs were analyzed. The protein BLChi79 (79.3 kDa) belongs to GH18 chitinases with a typical carbohydrate-binding module. Its optimum activity occurred at 60 °C and pH 6.0, with colloidal chitin as the optimal substrate. Mg2+, Fe2+, and Mn2+ boosted its activity, while K+, Cu2+, Zn2+, and Ca2+ suppressed catalysis. Its Km was 6.14 mg·mL−1, Vmax 7.78 μmol·min−1·mg−1, and kcat 10.16 min−1. The purified recombinant enzyme could degradethe C. elegans chitin layer and the P. equorum egg vitelline envelope. In summary, the BLChi79 derived from B. laterosporus targets chitin-enriched eggshells, acting as a green biocatalyst for controlling livestock gastrointestinal nematodes.