Chitinolytic enzymes production by two marine isolates of Aspergillus pseudoterreus and Sydowia polyspora and investigation of their antagonistic interactions against fungal pathogens

Marine fungi are one of the most promising group of organisms in terms of ecological diversity, new enzyme and secondary metabolites detection, application in environmental sciences. In the present work, in order to evaluate the biotechnological potential of two marine strains, Aspergillus pseudoterreus and Sydowia polyspora, the production and activity of chitinolytic enzymes were investigated. Moreover the in vitro antagonistic activity towards plant, human and animal pathogenic fungi was investigated. The strains were isolated from Ulva rigida and Sargassum muticum, collected along the coast of the Italian peninsula during a PhD thesis (Garzoli, 2013). Sydowia polyspora was obtained both from Ulva rigida and Sargassum muticum; Aspergillus pseudoterreus was isolated only from Ulva rigida.The studied fungi were inoculated in mineral medium added with colloidal chitin as the only carbon source; chitinase production was assayed by the DNS method which estimates the concentration of reducing sugars in the sample. The antagonistic activity was investigated by dual cultures (Skidmore & Dickinson, 1976). Results showed that: 1) both S. polyspora and A. pseudoterreus produced a good amount of chitinases; the maximum enzymatic yield was detected after 4 days for S. polyspora and after 7 days for A. pseudoterreus; 2) an interesting antagonistic activity was evidenced for A. pseudoterreus, able to inhibit the growth of A. fumigatus and P. oryzae. In conclusion, positive data regarding the chitinases production have been highlighted, even if these results cannot completely explain the antagonistic activity of the two marine strains against the tested pathogenic fungi.