Biochemical, functional and antioxidant dynamics potential of higher fungi cultivated on agro-industrial residues. Part I: Cultures on media supplemented with yeast extract, gypsum and commodity vegetable oils

Abstract

Mushroom cultivation is an implementation of the industrial biotechnology in the valorization of various lignocellulosic materials. In the present study, common lignocellulosic residues (wheat straw - WS and barley and oats straw - BOS) were supplemented with ‘novel’ compounds (sunflower and corn oil, yeast extract and CaSO₄⋅2H₂O) and their impact on the biochemical properties (composition of intra-cellular polysaccharides - IPSs, proteins, lipids, glucans, tocopherol content, carbohydrates and fatty acids composition), total phenolic compounds (TPCs) and the antioxidant activity of Pleurotus ostreatus and Pleurotus eryngii mushrooms, cultivated in ‘bag-logs’, was evaluated. Results revealed that supplements enhanced IPSs in carposomes cultivated on BOS substrates and the most positive were corn oil 2%, w/w and CaSO₄⋅2H₂O for P. ostreatus and P. eryngii, respectively (50.86 and 57.65%, w/w). In all treatments, there was a variety in the carbohydrate's composition and a great production of glucans (40.67–62.15%, w/w), especially of the bioactive β-glucans (32.10–61.93%, w/w) in the stipes of both species. Significant protein content was detected in P. ostreatus and P. eryngii carposomes grown on substrates with yeast extract (28.99 and 30.09%, w/w; WS and 29.49 and 24.94%, w/w; BOS). Although mushrooms presented a low lipid content in general, high values of fat content were observed for both species when cultivated on BOS substrate supplemented with sunflower and corn oil (4.54–6.58%, w/w). The nutritional value of mushrooms was comparable between the two flushes. The greatest amount of TPCs were detected in supplemented WS (22.31–35.30 mg gallic acid equivalents/g d.w.) and BOS (21.03–41.74 mg gallic acid equivalents/g d.w.) with CaSO₄⋅2H₂O, in all parts of mushrooms and a strong antioxidant activity and tocopherols production, in all treatments. A higher quantity of lipids, antioxidant activity and reducing power was present in the pilei rather than the stipes, while the latter were richer in IPSs, regardless of the supplement's presence. Therefore, the outlined supplemented substrates could be used to produce mushrooms with high nutritional and medicinal values.