production of trichoderma asperellum t8a spores by a "home-made" solid-state fermentation of mango industrial wastes

Abstract

Dry wastes (dw) generated in processing mangoes, composed (in dry weight) mainly of soluble carbohydrates (71 ± 2%) and fiber (16 ± 1%), were evaluated as substrates in a “home-made” solid-state fermentation (using polyurethane foam as inert support matrix, various C:N ratios, moisture contents, and incubation periods) of Trichoderma asperellum T8a, a promising biological control agent against the mango pathogen Colletotrichum gloeosporioides (causal agent of anthracnose). Highest spore production (2.5 x 106 up to 76 ± 3 x 108 spores g-1 dw) occurred after 8 days of incubation [at 28 ± 1 °C, relative humidity of 85 ± 5%, photoperiod of 12h (540 Lux) - 12h (20 Lux)] at a C:N ratio of 26, and a moisture content of 78%. Scanning electron microscopy showed that T. asperellum T8a was able to grow on mango industrial wastes and into polyurethane foam. The extensive growth can be related to cellulases secreted by this fungus, liberating glucose from these wastes to its growth. Most (94 ± 1%) of the spores grown on mango industrial wastes survived storage at 4 °C for 7 days and were equally effective as those grown on potato dextrose agar medium (86 ± 4% viable) in biological control tests against C. gloeosporioides ATCC MYA 456. Results indicate the potential use of mango industrial wastes as substrates to produce T. asperellum T8a spores in situ (mango orchards) under a cheap “home-made” solid-state fermentation, reducing problems associated with wastes disposal and permitting the production of a biological control agent against C. gloeosporioides.