Biochemical, functional and antioxidant potential of higher fungi cultivated on agro-industrial residues. Part II: Cultures on mixtures of spent mushroom substrates and mushroom cropping by-products

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Novel substrates consisted of different fresh agro-industrial residues, their corresponding and commercial spent mushroom substrates (i.e. SMS deriving from laboratory-scale experiments and SMS deriving from industrial-scale experiments by Green Zin S.A. - SMS GZ) and Pleurotus waste (PW; stipes/mishappen mushrooms) were used in blends for a new cultivation cycle of Pleurotus ostreatus and P. eryngii mushrooms in bags. Their impact on the biochemical properties (intra-cellular polysaccharides - IPSs, protein, lipid, total phenolic compounds - TPCs, individual carbohydrates composition of the IPSs) in the first- and second-flush whole mushrooms, pilei and stipes, as well as the fatty acids composition, the antioxidant activity (in the first-flush mushroom parts) and glucan content of stipes were examined. Both species produced satisfactory IPSs quantities in all substrates (28.69–46.38 %, w/w) and significant protein amounts (18.37–26.80 %, w/w). The further SMS addition (80 %, w/w instead of 40 %, w/w) in the cultivation substrates affected positively the mushroom IPSs values, whereas the highest protein content was detected in mushroom's parts cultivated on substrates consisted of fresh agro-industrial residues. Mushroom's lipid content was affected differently by the various substrate combinations, with SMS presence resulting in mushrooms with a lower fat content than those produced in substrates with PW addition. Fresh substrates with PW and those with coffee residue were the most favorable for TPCs production. Regarding production flushes, the nutritional value of mushrooms was comparable between them, only a slight increase in TPCs of second-flush carposomes was detected. Glucose was the predominant monosaccharide of the produced IPSs, combined with a significant production of total and β- glucans. SMSs and PW addition had a positive impact on antioxidant activity, too. A higher quantity of lipids, TPCs and significant antioxidant activity were detected in all Pleurotus pilei than stipes, whereas the latter were richer in IPSs. Both pilei and stipes had a significant protein amount. Hence, the data obtained by this study support the positive effect of different types of SMS and mushroom waste on P. ostreatus and P. eryngii nutritional value.