The influence of supplemental components in nutrient medium on chitosan formation by the fungus Absidia orchidis

Chitosan, a derivative of chitin, is a natural component of some fungus cel l walls. It is formed by the complex action of chitin synthase and chitin d eacetylase. The in vitro activity of these two enzymes is known to be influ enced by several factors. We investigated the influence of ferrous ions, ma nganese ions, cobalt ions, trypsin, and chitin, as individual supplements t o the nutrient medium, on the in vivo activity of chitin synthase and chiti n deacetylase to form chitosan in the fungus Absidia orchidis. Manganese an d ferrous ions gave the most significant results. These ions increase chito san yields through an increase in biomass production rather than an increas e of chitosan content in cell walls. Manganese and ferrous ions lowered the activity of chitin de acetylase; however, their influence on the activity of chitin synthase was more complex. The effects of trypsin and chitin on b iomass and cell wall chitosan content were negligible, while cobalt ions co mpletely inhibited the growth of fungi.