Addition of abscisic acid increases the production of chitin deacetylase by Colletotrichum gloeosporioides in submerged culture

The activity of chitin deacetylase from Colletotrichum gloeosporioides was studied by the addition of phytohormones (gibberellic acid, indole acetic acid, and abscisic acid) and amino sugars (glucosamine and N-acetyl glucosamine) in culture media. Abscisic acid exerted a positive and significant effect on enzyme production with 9.5-fold higher activity (1.05 U mg protein⁻¹) than the control (0.11 U mg protein⁻¹). Subsequently, this phytohormone was used in batch culture with higher chitin deacetylase activity being found at acidic pH (3.5) than at neutral pH (7). Furthermore, the highest activity was determined at the acceleration growth phase. The chitin deacetylase production was ascribed to the lag phase within the spore germination process and germ tube elongation instead of during the formation of appressoria, as evidenced by the scanning electronic microscopy results. Therefore, more inoculum and medium containing abscisic acid were added to the fed-batch culture, resulting in a significant increase in chitin deacetylase activity (3.64 U mg protein⁻¹). The addition of abscisic acid led to changes in the acetylation degree of chitin extracted from the cell wall of C. gloeosporioides, with lower degree of acetylation (DA of 75.6%) than that determined with the culture without abscisic acid (DA of 90.6%).