Substrate–fungus interaction on the enzymatic and non‑enzymatic antioxidant activities of solid state fermentation system

The fungus–substrate interaction on the antioxidant activity of a solid state fermentation system (SSFS) was investi‑
gated employing two basidiomycete fungi: Pleurotus columbinus and P. foridanus and two ascomycetes: Aspergillus
fumigatus and Paecilomyces variotii on powdered peels of banana, pomegranate and orange, empty pea pods and
rice straw. The oven‑dried substrates were moistened at 90% water holding capacity, inoculated with the test fungi
and incubated at 25 °C for appropriate time. Culture extracts were tested for the enzymatic and non‑enzymatic
antioxidant activity. The efect of substrate on the antioxidant activity of the SSFS was stronger than that of the fungal
species. Peroxidase (POX) activity was higher in the basidiomycetes than ascomycetes and achieved its maximum in P.
foridanus versus complete absence in A. fumigatus. By contrast, catalase (CAT) activity was higher in the ascomycetes,
particularly P. variotii on banana peel, than in the basidiomycetes. Phenolics and favonoids were highest in pome‑
granate peels but lowest in banana peels and rice straw, and they were subjected to severe consumption by the
basidiomycetes versus mild production by the ascomycetes. The reducing power (RP) and DPPH scavenging activity
were higher in the peels of pomegranate, orange and banana relative to rice straw and empty pea pods, and the fun‑
gal efect was limited and independent of the fungal taxonomic group. Orange peel is the appropriate substrate for
production of fungal CAT and POX, which activities were mutually exclusive; but pomegranate peel is more suitable
for production of phenolics and favonoids.