Chitosan produced from Mucorales fungi using agroindustrial by-products and its efficacy to inhibit Colletotrichum species

This study evaluated corn steep liquor (CSL) and papaya peel juice (PPJ) in mixture as substrates for the cultivation (96 h, 28 °C, pH 5.6, 150 rpm) of Mucorales fungi for chitosan production, and determined the growth-inhibitory effect of the fungal chitosan (FuCS) obtained under optimized conditions against phytopathogenic Colletotrichum species. All Mucorales fungi tested were capable of growing in CSL-PPJ medium, showing FuCS production in the range of 5.02 (Fennelomyces heterothalicus SIS 28) − 15.63 mg/g (Cunninghamella elegans SIS 41). Highest FuCS production (37.25 mg/g) was achieved when C. elegans was cultivated in medium containing 9.43% CSL and 42.5% PPJ. FuCS obtained under these conditions showed a deacetylation degree of 86%, viscosity of 120 cP and molecular weight of 4.08 × 104 g/mol. FuCS at 5000, 7500 and 10,000 ppm inhibited the growth of all Colletotrichum species tested. FuCS also induced alterations in the morphology of C. fructicola hyphae. CSL-PPJ mixtures are suitable substrates for the cultivation of Mucorales fungi for FuCS production. Chitosan from C. elegans cultivated in CSL-PPJ medium is effective in inhibiting phytopathogenic Colletotrichum species.