초록
An antagonistic bacterium Pseudomonas stutzeri YPL-1 liberated extracellular chitinase and $\beta$-1,3-glucanase which are key enzymes in the decomposition of fungal hyphal walls. The lytic enzymes caused abnormal swelling and retreating at the hyphal tips of plant pathogenic fungus Fusarium solani in a dual culture. Scanning electron microscopy revealed the hyphal degradation of F. solani in the regions interacting with P. stutzeri YPL-1. The production of chitinase and properties of a crude preparation of the enzyme from P. stutzeri YPL-1 were investigated. Peak of the chitinase activity was detected after 4 hr of cultivation. The enzyme had optimum temperature and pH of 50$^{\circ}C$ and pH 5.3, respectively. The enzyme was stable in the pH range of 3.5 to 6.0 up to 50$^{\circ}C$. The enzyme was significantly inhibited by metal compounds such as $HgCl_2$, but was stimulated by $CoCl_2$. P. stutzeri YPL-1 produced high levels of the enzyme after 84 hr of incubation. Among the tested carbon sources, chitin was the most effective for the enzyme production, at the concentration level of 3%. As a source of nitrogen, peptone was the best for the enzyme production, at the concentration level of 4%. The maximum amount of enzyme was produced by cultivating the bacterium at a medium of initial pH 6.8.