Properties of Chitinase-Producing Bacterium, Pseudoduganella plicata SG-4 Isolated from Kaempfer Cicada (Platypleura kaempferi) Exuviae

Chitin is among the world’s most abundant biopolymers, found in the cell walls of fungi, the exoskeletons of crustaceans, and the exuviae of insects. In this study, we report on the properties and potential of Pseudoduganella plicata SG- 4, chitinase-producing bacterium isolated from cicada exuviae. P. plicata SG-4 exhibited high chitinase activity, with values of 11 U/mL at 2 days in chitin medium. P. plicata SG-4 exhibited major chitinase bands at 250, 68, 49, 45, and 38 kDa. Notably, the chitinase activity of SG-4 was lost in the presence of β-mercaptoethanol. The degradation patterns of chitinase from SG-4 strains, analyzed by thin layer chromatography (TLC), confirmed that the bacterium produced endo-chitinase. Chitinase from the SG-4 strain was partially purified using an affinity column filled with regenerated chitin. The partially purified enzyme was identified on SDS-PAGE gels, showing major chitin bands at 250 and 45 kDa. The optimum pH and temperature for this enzyme were pH 9 and 40 ℃, respectively. Meanwhile, from the electrophoresis results of the partially purified enzyme, proteins of 82 and 60 KDa presumed to be chitin binding proteins could be identified. P. plicata SG-4 produced chitinase, protease, amylase, and lipase. This strain also exhibited plant growth promotion properties such as nitrogen fixation, IAA production, and ammonia production. Furthermore, P. plicata SG-4 reduced the growth of Colletotrichum gloeosporioides, a fungal plant pathogen, by approximately 63%, indicating significant biological control potential. Our study provides foundational information on the chitin-degrading abilities of P. plicata SG-4, highlighting the potential for the commercial use of P. plicata SG-4 enzymes, particularly for promoting plant growth and inhibiting C. gloeosporioides.