Characterization and Biocontrol Potential of a Novel Endochitinase CaChi19B from Chitinilyticum aquatile

GH19 (glycoside hydrolase family 19) chitinases are essential for the enzymatic degradation of chitin and play crucial roles in the biocontrol of phytopathogenic fungi and nematodes. In this study, a novel endochitinase of GH19 (CaChi19B) was successfully cloned from Chitinilyticum aquatile CSC-1 and heterologously expressed in Escherichia coli. CaChi19B displayed optimal activity at 40 °C and pH 6.5. It demonstrated a higher stability below 50 °C. CaChi19B exhibited substrate specificity for colloidal chitin (CC), α-chitin, and β-chitin. Analysis of the hydrolysis products revealed that CaChi19B exhibited endoacting activity toward CC substrates. Notably, CaChi19B demonstrated antifungal activity against Coniothyrium diplodiella and Aspergillus sydowii, inhibiting their hypha growth by 22.3 and 16.5%, respectively. Additionally, it exhibited nematicidal effects against Caenorhabditis elegans and the plant parasitic nematode Meloidogyne, with LC₅₀ values of 1.66 and 0.36 mg/mL, respectively. This marks the first report of such activity in Chitinilyticum-derived chitinases. These findings suggest that CaChi19B has promising potential as a biocontrol agent in agriculture, offering an environmentally friendly alternative to synthetic pesticides.