The Golden touch – Fungal bioconversion of agroindustrial waste in high value compounds

Reuse what you can, recycle what cannot be reused, repair what is broken, remanufacture what cannot be repaired1. These are the main pillars of the circular economy system. In spite of a linear economy system, these sustainable processes would turn goods that are at the end of their service life into resources for others. This is the way to close loops in industrial ecosystems and minimize waste, a concept that should soon disappear. Is it feasible? Microbial biodiversity could help to change the fate of agroindustrial wastes, transforming them in new products. Thanks to their natural capability to grow on cellulose and lignin, fungi could be good candidates. Fungal fermentation is independent from land exploitation, being ethical sustainable by not competing with food and farm industry. In the optimal conditions, fungal growth could be economic and energetic sustainable, as required by the principle of the green economy. Within the Fungal Kingdom, a great variety of fungal features and metabolic pathways could be found. Unfortunately, this metabolic richness is still poorly known. Moreover, several fungi are edible, and some have a good nutritional quality, being rich in protein, polysaccharides, with low rate of fatty acids, high PUFA levels, and other nutritional compounds as vitamins and essential amino acids. Basidiomycetes and Ascomycetes have been used for centuries as folk medicines, especially in Asian countries, where their medicinal properties are well known. The immunomodulatory and antitumoral properties of substances extracted from various species of edible mushrooms are now also extensively recognized at a scientific level. This project was aimed to investigate the methods to produce such a high-value biomass with low economic and environmental impact. In particular, this work was aimed to find fungal strains which could grow on agroindustrial waste, as for example food industry or insect breeding wastes. These wastes could then find a new exploitation to have good biomass yields, with the desired nutritional features. In this work, medicinal mushrooms have been selected, including Pleurotus ostreatus and Ganoderma lucidum, both known to metabolise many kinds of substrates and to contain a wide variety of bioactive components. To investigate their ability to metabolise agroindustrial wastes and transform them in high value products, media composition was designed using not-easily accessible C and N sources. Twenty cultural lines were set up in submerged fermentation using different wastes. The first goal was to evaluate how biomass production yields were affected by different C and N sources and their ratio. Preliminary results about the biomass recovery and the fungal ability to metabolise agroindustrial wastes look very promising. More in details, fungal strains were able to grow in the presence of most of the media and, in particular, in the presence of insect breeding wastes where the biomass recovery was comparable to the control. Additional efforts are now focused to study the fungal broths and the biomass extracts. They will be analysed from a nutraceutical point of view, evaluating also their antioxidant and radical scavenging properties using spettrophotometric assays. For instance, Folin-Ciocalteu test, ABTS and DPPH assays will be used to assess the presence of bioactive molecules that could a positive outcome on animal and human health.