Abstract

Several chitinases with nematicidal action of these fungi have been identified in recent years, however, little is known about which nutritional factors from the culture medium are significant for its mass production. The aim of this study was to perform the statistical screening of the components of the culture medium for chitinase production by nematophagous fungi, Monacrosporium sinense (SF53) and Monacrosporium thaumasium (NF34) aiming to identify which of these components were significant and to evaluate the influence of pH on chitinase activity of these fungi. The effect of five variables (chitin, colloidal chitin, glucose, sodium nitrate and moisture) on chitinase production was analyzed using Plackett-Burman statistical design. Chitinase activity was determined at different pH (pH 3.5, 4.5 and 5.5) and Tris-HCl 50 mM (pH 7.0 and 8.0). In relation to the isolate NF34, at the levels evaluated, two variables were significant (p <0.05) for chitinase production: chitin and NaNO₃. On the other hand, for SF53, at the levels evaluated, only glucose was significant (p <0.05). Regarding the influence of pH on enzyme activity for M. thaumasium the pH value with the highest activity obtained was 5.5. However, for M. sinense, the highest activity was observed at pH 8. These data demonstrate that different species of nematophagous fungi may exhibit better enzymatic activities and consequently, better predatory activities at different environmental conditions.

Key words: Nematophagous fungi, chitinase, Plackett-Burman, nematicidal action, Monacrosporium thaumasium, Monacrosporium sinense.