The composition of the substrate is one of the most critical factors influencing the quality as well as the nutritional value and bioactive content of mushrooms. Therefore, the effects of various substrates, such as barley and oat straw (BOS), beech wood shavings (BWS), coffee residue (CR), rice bark (RB) and wheat straw (WS, control substrate), on the biochemical properties (lipid, protein, polysaccharide, glucan, ash, and mineral content, fatty acids and tocopherols composition), total phenolic compounds and antioxidant activity of Pleurotus mushrooms, P. ostreatus (strains AMRL 144, 150) and P. eryngii (strains AMRL 166, 173-6), cultivated in ‘bag-logs’, was examined. Proximate analysis of A. bisporus and A. subrufescens grown on two different composts (C/N ratios of 10 and 13) was conducted, too. The whole carposomes, pilei and stipes were analyzed. Results showed that BOS, RB, BWS and CR improved the antioxidant activity of Pleurotus species and their nutritional characteristics. Both pilei and stipes were rich in polysaccharides (27.51–67.37 and 22.46–39.08%, w/w, for Pleurotus and Agaricus spp., respectively), lipids (0.74–8.70 and 5.80–9.92%, w/w), proteins (6.52–37.04 and 25.40–44.26, w/w, for Pleurotus and Agaricus spp., respectively) and total phenolic compounds (10.41–70.67 and 7.85–16.89 mg gallic acid equivalent/g for Pleurotus and Agaricus spp., respectively), while they contained important quantities of unsaturated FAs of nutritional and medicinal importance. Pilei were richer in proteins, total phenolic compounds and enhanced antioxidant activity and reducing power than stipes, whereas stipes were richer in IPSs and glucans compared to the corresponding pilei. Thus, mushroom cultivation could upgrade rejected agro-industrial residues and wastes to new uses as substrates for the production of mushrooms with specific nutritional and medicinal attributes.

Background: The effect of substrate and strain on the nutritional and functional properties of mushroom flours and protein concentrates (PCs) has not thoroughly been investigated. Methods: The proteins of P. ostreatus flours (strains AMRL144 and 150) were isolated following alkaline extraction (pH 12) and isoelectric precipitation (pH 4) as it was determined by the solubility curves. The protein quality of the flours and PCs were evaluated by determining the protein solubility index (PSI) and their functional properties, such as water (WAC) and oil absorption capacity (OAC), foam capacity (FC), foam stability (FS) and emulsion stability (ES). The amino acid (AA) composition of the flours was determined by reversed-phase liquid chromatography after protein hydrolysis and o-phthalaldehyde derivatization. Results: The PSIs of the flours and PCs of P. ostreatus were comparable to those of soy protein flours and protein concentrates. The highest AA concentration was found for both strains when cultivated on the barley and oat straw (BOS) substrate, showing a similar trend as the protein content. A principal component analysis (PCA) indicated an impact of the strain on the functional properties. Conclusions: Both strains can produce high quality proteins especially when cultivated on wheat straw (WS). The FS was positively correlated with the P. ostreatus strain AMRL150 whereas the FC was positively correlated with AMRL144.

Agricultural residues, including Pleurotus ostreatus spent mushroom substrate (SMS) and roots of (hydroponic) leafy vegetables (RLV), were tested in various proportions as substrates in new P. ostreatus cultivations, where wheat straw was the control. The impact of SMS and RLV was first evaluated by the mycelial growth rate (Kr, mm/day). Afterwards, mushroom cultivation was conducted in bags, where production characteristics like earliness (the time from substrate inoculation to first harvest) and biological efficiency (BE %, the ratio of fresh mushroom weight to dry substrate weight × 100) were examined. The study also evaluated mushroom quality, nutritional composition and bioactive content. The highest intra-cellular polysaccharide (IPS) value (50.93%, w/w) was observed in the substrate containing SMS 90%, while combining SMS with RLV resulted in higher IPS values compared to mixtures that also included wheat bran (WB) and soybean flour (SF). Furthermore, the use of RLV reduced the fat content compared to the control substrate, except in the case of the SMS 50%–RLV 40% substrate, where the highest fat content was observed in the produced mushrooms (4.68% w/w). Additionally, the protein content increased with the use of RLV. The highest triterpene content was found in the SMS 90%–RLV 10% (11.52 ursolic acid mg/g d.w.). However, the control substrate exhibited the fastest Kr (6.5 mm/d), as well as the highest BE (87.8%) and total phenolic compound value (30.31 mg GAE/g d.w.). Significant antioxidant activity was observed in all extracts, while the total flavonoid content was low. Glucose was the dominant monosaccharide (over 51.5%, w/w), and linoleic acid (18:2; over 57.05%, w/w) was the primary fatty acid across all mushrooms. This study also enhances our knowledge by which SMS and RLV influence the NFE2L2/HMOX-1 molecular pathway, thereby affecting specific antioxidant-related genes. These effects were observed through the impact of P. ostreatus protein and carbohydrate extracts on LPS-challenged THP-1-derived macrophages. A positive impact on the gene expression of HMOX1, CAT and NFE2L2 during incubation with the aforementioned samples was observed. These findings support the sustainable use of agricultural by-products in mushroom cultivation, offering an environmentally friendly approach while producing valuable products like mushrooms.

Agricultural activities produce large quantities of organic byproducts and waste rich in lignocellulosic materials, which are not sufficiently utilized. In this study, alternative agricultural waste products, namely, spent mushroom substrate (SMS) from the cultivation of edible Pleurotus ostreatus mushrooms and the roots of leafy vegetables from hydroponic cultivation (HRL), were evaluated for their potential to be used as substrates for the cultivation of Pleurotus citrinopileatus and their effects on the quality, the nutritional value, the chemical properties (lipid, protein, carbohydrate, ash, fatty acid and carbohydrate composition) and the bioactive content (total phenolic compounds and antioxidant activity) of produced mushrooms. SMS and HRL (in different ratios with and without additives) and wheat straw with additives (WS—control) were used. During incubation, the linear growth rate of the mycelium (Kr, mm/day) was measured and used for screening. Mushroom cultivation took place in bags, where several characteristics were examined: earliness (duration between the day of substrate inoculation and the day of first harvest) and biological efficiency (B.E. %, the ratio of the weight of fresh mushrooms produced per dry weight of the substrate × 100). Furthermore, this study aimed to investigate the effect of the protein extract (PE) and carbohydrate extract (CE) of P. citrinopileatus after in vitro digestion (fraction less than 3kDa: PE-DP-3; digestate fraction: CE-D, respectively) on the expression of antioxidant-related genes in the THP-1 cell line. The results showed that mushrooms grown on SMS 50%-HRL 40% had the fastest growth (6.1 mm/d) and the highest protein and lipid contents (34.7% d.w.; 5.1% d.w.). The highest B.E. (73.5%), total carbohydrate (65.7%) and total phenolic compound (60.2 mg GAE/g d.w.) values were recorded on the control substrate. Antioxidant activity was observed in all extracts; the total flavonoid content was low in the samples, and the maximum total triterpene value was detected in SMS 80%-HRL 20% (9.8 mg UA/g d.w.). In all mushrooms, linoleic acid (C18:2) was the main fatty acid (above 60%), and fructose was the dominant individual saccharide. In the investigation of the regulation pathway, NFE2L2 gene expression was upregulated only in the SMS 60%-HRL 40% intervention during incubation with CE-D samples. Additionally, the transcription levels of antioxidant-related genes, SOD1, CAT, HMOX1 and GSR, were increased in the SMS 60–30% intervention. Compared to WS, the alternative substrates are observed to trigger a pathway concerning CE that may resist oxidative stress. This study supports the utilization of agricultural byproducts through sustainable and environmentally friendly practices while simultaneously producing high-value-added products such as mushrooms. Therefore, alternative substrates, particularly those containing HRL, could serve as natural sources of antioxidant potential.

Spent mushroom substrate (SMS), spent coffee grounds from espresso production (SCG), faba bean harvest residues (FBR), pistachio shells (PS) wheat straw (WS) (control) agro-industrial waste were combined in different ratios, with or without supplements (wheat bran, soybean flour), to create novel substrates for Pleurotus columbinus growth. The impact of the substrates on the mycelial growth rate (Kr), biomass production, laccase, total cellulases and carbohydrate synthesis, along with the C and N consumption by P. columbinus, were examined in fully colonized substrates. The incubation period, earliness and biological efficiency (B.E.) (%) were also determined. Then, the intracellular polysaccharide (ICP) contents of the P. columbinus produced mushrooms were evaluated in the most promising substrates. P. columbinus was grown successfully in a wide range of C/N ratios of substrates and the fastest Kr (7.6 mm/d) was detected on the 70 SMS-30 FBR, without supplements, whereas substrates consisting of SCG enhanced biomass production (700.0–803.7 mg/g d.w.). SMS and PS or SCG led to the shortest incubation and earliness period of P. columbinus. The C content was reduced and the N content was substantially increased in all the colonized substrates. The 70 SMS-30 FBR and 80 SMS considerably enhanced the laccase production (up to 59,933.4 U/g d.w.) and substrates consisting of PS promoted total cellulases activities. Greater amounts of carbohydrates (3.8–17.4 mg/g d.w.) than that in the control were recorded for all the substrates. The combination of SMS and SCG or WS led to the highest B.E. values (59.3–87.1%) and ICP amounts (34.7–45.9%, w/w), regardless of the supplement addition. These findings support the effective utilization of agro-industrial waste in P. columbinus cultivation, producing high-value-added compounds and supporting mushroom growth.

The present study investigated the cultivation of Pleurotus columbinus on alternative substrates derived from spent mushroom substrate combined with spent coffee grounds or wheat straw, with or without supplementation with wheat bran and soybean flour, in comparison to conventional wheat straw. All substrates were evaluated for their effects on the nutritional composition, amino acid profile, lipid, carbohydrate contents and bioactive compounds of the harvested carposomes. Protein content ranged from 15.6 to 21.4% w/w. Methionine was identified as the first limiting amino acid and the essential amino acid index was up to 60.9%. Carbohydrate content exceeded 63.3% w/w in all samples, with glucose identified as the major monosaccharide. Lipid content was low (1.7–3.4% w/w), with polyunsaturated fatty acids predominating. Ash content ranged from 5.7 to 6.3% w/w and the energy value varied between 36.2 and 37.1 kcal/100 g f.w. Bioactive compounds, including β-glucans (35.9–44.4% w/w) and ergosterol (3.3–4.7 mg/g d.w.), along with their metabolites, were successfully quantified. Non-supplemented substrates enhanced β-glucan levels; most of them were further isolated, whereas lovastatin was not detected in any sample. Overall, P. columbinus cultivated on alternative substrates exhibited improved nutritional quality and higher bioactive compound content compared to conventional cultivation, demonstrating the potential of agro-industrial by-products as sustainable substrates for high-value mushroom production.