Purification and characterization of Stenotrophomonas maltophilia chitinase with antifungal and insecticidal properties

This study aimed to determine the ability of bacteria to produce the chitinase enzyme, purify, and characterize the enzyme from the isolate with the best activity, and determine the use of this purified enzyme as a biocontrol agent. The chitinolytic bacterium was identified as Stenotrophomonas maltophilia. The chitinase enzyme was purified 1.4 times at a 30% ammonium sulfate concentration with a yield of 40.7%. Following partial purification, the enzyme was purified by ion-exchange chromatography using HiPrep Q XL 16/10 column and HiPrep™ 26/10 desalting column with 25.34% and 18.12% yields, respectively. It was calculated that the purified enzyme had a molecular weight of 52 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The optimum activity of the enzyme was determined at 50 °C and pH 7.0. Enzyme activity was most induced by Fe2+, while it was most inhibited by Zn2+ at 5 mM concentration. Km and Vmax values of the enzyme for colloidal chitin were calculated as 1.6419 mg/mL and 16.129 U/mg, respectively. The purified chitinase was used as a biocontrol agent against the fungus Fusarium oxysporum and potato beetle Leptinotarsa decemlineata. The enzyme was shown to be effective in reducing the growth of fungus and causing disruption of the chitin structure of potato beetle.