This project deals with using crop residues to produce food by cultivating mushrooms. Mushrooms are edible fungi that can grow on residues from agriculture and forestry. Mushrooms are rich in protein, which can partially substitute meat. The protein in fungi is more friendly to the environment than the protein of animal origin.
When edible fungi are harvested, a solid residue termed spent mushroom substrate (SMS) is generated. SMS is the primary residue of mushroom cultivation. SMS is generated in large amounts and is a waste material with no economic use. SMS accumulation causes environmental problems, such as the generation of greenhouse gases, foul odors, and contamination of water sources. It is essential to find ways to valorize SMS. That will decrease environmental pollution and improve the sustainability of the mushroom industry.
Our project deals with SMS valorization. We will investigate how to recover from SMS bioactive compounds and sugar. Bioactive compounds are substances, such as antioxidants, which have high value for producing medicaments and food. Sugar produced from SMS will be used for cultivating oleaginous yeasts, i.e., microbes that are rich in lipids. Yeast lipids can substitute imported plant oil and thus decrease the environmental burden. Plant oil production often requires considerable land use and rainforest clearing for planting soybean and other crops in countries exporting oil to Europe.
The project will also investigate how to use SMS as biofertilizer and soil amendment. That will allow substitution of mineral fertilizers. Mineral fertilizers have fossil origin, and their substitution is vital for sustainability in agriculture.
Another use of SMS that will be investigated in the project is the bioremediation of wastewater. That will allow the use of treated wastewater for irrigation, decreasing the demand for freshwater. The impact of SMS bioremediation on freshwater ecosystems will be evaluated.
MUSA intends to contribute to enhancing agriculture sustainability by (i) using crop residues for producing edible fungi, and (ii) upgrading spent mushroom substrate (SMS), the main by-product of mushroom farming, for uses supporting food production, substitution of mineral fertilizers and providing wastewater bioremediation solutions.
The Norwegian researchers participating in the project will (i) extract bioactive compounds from SMS, (ii) investigate the enzymatic conversion of cellulose contained in SMS, (iii) prepare cellulosic hydrolysates to be used for cultivating oleaginous yeasts, (iv) recovery of lignin from SMS saccharification residues using green solvents, (v) assess SMS as biofertilizer and soil amendment, and (vi) evaluate the effects of using SMS-based wastewater bioremediation on freshwater ecosystems.
The project will develop extraction methods that preserve the properties of targeted compounds and minimize degradation of non-targeted molecules. The extracts will be evaluated as food additives, and the extraction residue will be subjected to saccharification for producing sugars that will serve as substrates for oleaginous yeasts. The produced yeast will be directed to extraction of lipids that can contribute to decrease the environmental impact of production of palm-, soybean- and rapeseed oil. The lipid-free biomass will be subjected to extraction of carotenoids and ß-glucans, which are bioactive compounds with antioxidant and immunostimulant activity.
The agronomic benefits of using of SMS as a biofertilizer in horticulture or as a soil amendment in agriculture will be quantified. Microbial communities in SMS, and correlations between specific microbes and SMS effectivity as biofertilizer will be assessed.
A bioremediation approach using SMS for removal micropollutants from wastewater to be used for irrigation will be developed. The SMS effects on water quality indicators will be addressed, and its impact on water ecosystems will be elucidated.