Abstract
Eight chitinolytic fungal species belonging to 5 genera (400 colonies /g dry soil) were isolated, from agricultural soil sample located in Al-Madinah Al-Munawarah, Saudi Arabia, on agar plates containing crude shrimp shell chitin. Trichoderma viride was the most dominant species (35% of the total count) followed by genus Fusarium (30% of the total count) which comprised of Fusarium poae, Fusarium bulbigenum var. lycopersici, Fusarium moniliform and Fusarium chlamydosporum. The other species were Chaetomium globosum (15% of the total count), Aspergillus fumigatus and Cephalosporium curtipes (10%, each). Estimation of chitinolytic activity on agar plates and submerged culture, by the recovered fungal species, was not always matched with their density on the isolation plates. However, the most dominant T. viride achieved the strongest activity. Maximum production of enzyme by the most potent T. viride was attained when grown in a medium with pH 4 and incubated for 6 days at 28 degrees C. The use of 1.5 g% colloidal chitin, as a sole carbon source, was superior for the enzyme induction. However, addition of other carbon sources to the colloidal chitin exerted a strong significant suppression for the induction. Presence of organic nitrogen source like peptone (0.25%) followed by yeast extract stimulated the enzyme production but ammonium nitrogen was suppressive. Metal salts as FeSO4 and ZnSO4 enhanced the enzyme productivity. The optimized crude chitinase exhibited strong antifungal activity against some food spoiling moulds.