Food waste to biomass approach: A sustainable strategy for the production of alternative microbial culture media for filamentous fungi growth

The valorization of organic waste is still one of the challenges in the path towards environmental sustainability and a circular bioeconomy. This research aimed at assessing the ability of three substrates of organic residues (olive pomace, potato peels and the green seaweed Ulva lactuca) to be used as alternative culture media for filamentous fungi. Mycelial growth on these media was compared with the conventional Potato Dextrose Agar (PDA) and Sabouraud media using three fungal species namely Fusarium oxysporum (F1), Fusarium solani (F2) and Alternaria alternata (N2) as biological models. The alternative media were made from waste materials, supplemented or not with glucose, and sterilized prior to the use. The measurements of mycelial growth were taken every day for 8 days and the data analyzed by multi-factorial ANOVA. Mycelial growth in all the waste-based media was found to be comparable to commercial media. Highest overall growth was seen in commercial PDA and Sabouraud media (19.9% and 19.3%) respectively. The glucose enriched formulations showed 13.2% (olive pomace) and 11.0% (potato peel) rich media with the remaining media showing less. The percentages of olive pomace, potato peels and U. lactuca were 12.9%, 9.3% and 1.2%, respectively, without the addition of glucose. Growth was significantly higher with glucose supplementation, showing the beneficial effect of the exogenous C supply and intrinsic nutritional value of the substrates. ANOVA revealed that incubation time and medium type significantly influenced mycelial growth across all three strains (p < 2.2 × 10-16), with significant interactions between medium and time (F1: F = 3.91, p = 6.08 × 10-10, F2: F = 163.31, p < 2 × 10-16, N2: F = 44.30, p < 2 × 10-16). The overall analysis of the three strains also indicated highly significant main effect for strain (F = 645.22) and incubation time (F = 391.95) as well as highly significant main effect for culture medium (F = 44.18) (all p < 2.2 × 10-16). Variations in texture and color that can be seen in the different media, however, may influence the macroscopic appearance of the mycelium and identification. Hence, these alternative media are recommended for post identification, subculture and preservation of fungal strains especially.