Sepedonium sp. and Phellinus sp. Novel Isolates: Growth Pattern and Production of Polysaccharide-Protein Complexes on Conventional and Grape Pomace Substrates

Abstract Purpose The growth behavior of novel fungal isolates along with the production of bioactive compounds from mycelia mass during submerged fermentations were investigated using conventional synthetic media and agro-industrial residues as fermentation substrates. Methods Four novel isolated fungi, belonging to edible or medicinal species, were evaluated for their ex-situ growth on potato dextrose agar. Specific attention was designated to Sepedonium sp. and Phellinus sp. considering their high growth rate in solid state fermentations. Submerged fermentations were subsequently employed using synthetic carbon sources (glucose, fructose and lactose) to assess the fermentation behavior. Following the better growth pattern on glucose and fructose, compared to lactose, grape pomace extract (GPE) was applied as nutrient feedstock to assess the production of biomass and bioactive compounds. Aqueous extraction was performed to obtain crude intracellular polysaccharides (IPS), that were subsequently characterized in terms of antioxidant activity, protein and polysaccharide content. Results Sepedonium sp. demonstrated the highest biomass production; 11.4 and 10.5 g/L, using glucose and fructose, respectively, whereas Phellinus yielded up to 3.8 g/L. Lactose was also assimilated by both fungal strains, however biomass production was lower. Utilization of GPE affected biomass production; Sepedonium sp. biomass decreased, whereas biomass obtained from Phellinus sp. was enhanced, compared to synthetic sugars. Crude IPS extracts elicit high antioxidant activity (> 75% inhibition of DPPH • free radical). Conclusion The successful application of conventional and renewable substrates for Sepedonium and Phellinus fermentation was demonstrated, while the mycelia mass derived polysaccharide-protein complexes exhibited bioactive properties, and thus might be utilized as functional food components. Graphical Abstract