No previous study assessed the combined effect of olive pruning residues (OLPR) and spent coffee grounds (SCG) on P. ostreatus production and nutritional value. The aim of this study was to determine the capacity of P. ostreatus to degrade lignocellulosic nature of combined OLPR and SCG as well as their resultant nutrient composition. A complete randomized design was adopted with five treatments: S1:100%wheat straw (WS) (control), S2:33%WS+33%SCG+33%OLPR,S3:66%WS+17%SCG+17%OLPR,S4:17%WS+66%SCG+17%OLPR, and S5:17%WS+17%SCG+66%OLPR, and ten replicates per treatment. Substrate’s and mushroom’s composition were analyzed on chemical scale, including fatty acids and heavy metals profiles, following international standards. Only S1, S2, and S3 were productive, with comparable biological yield, economical yield, and biological efficiency. Organic matter loss decreased with increasing proportions of OLPR and SCG. Percentage lignin loss was higher in S1 than in S2 and S3 (53.51, 26.25, and 46.15% respectively). Mushrooms of S3 had some enhanced nutritional attributes compared to control: decrease in fat, increase in protein, increase in monounsaturated fatty acids, and lower zinc accumulation. Lead was less accumulated in S2 than S1 mushrooms. Sodium content of mushroom decreased in S2 and S3. The latter substrates yielded mushrooms with lower polyunsaturated fatty acids (PUFA) and higher saturated fatty acids (SFA) contents. All mushrooms had a valuable PUFA/SFA. This study suggests using OLPR and SCG in low proportions as nutritional supplements to the commercial wheat straw.

Supplementation of the growing substrate by nitrogenous additives has been known to improve the production of oyster mushroom (Pleurotus ostreatus (Jacq. ex Fr.) P. Kumm. (1871)). However, the application of nano-additives has not been reported in such cultivation yet. The study investigated the effect of nano-urea added in two different doses (3 g and 5 g per kg substrate), once (at spawning or after first flush) or twice (at spawning and after first flush) to the growing substrate consisting of wheat straw and spent oyster substrate (1:1, w/w). Results showed that the application of nano-urea once has induced the highest number of mushroom flushes (four flushes) despite the dose applied. Contrarily to early findings, where high doses of nitrogen have caused inhibition of mushroom growth and production, nano-urea application has had better effects when applied twice. With 5 g/kg, it induced the shortest period between the first and the third flush (15 days). With 3 g/kg, it resulted in the highest biological and economic yields at the third flush (332.7 g/bag and 283.1 g/bag respectively), in total (973.4 g/bag and 854.0 g/bag respectively), the highest biological efficiency (109.6%), and pileus diameter/stipe length ratio (2.8). Experimental findings of the current study may be potentially applied at commercial scale.

The work investigated the effect of Lithovit-Urea50 on the composition of Pleurotus ostreatus (Jacq. Ex Fr.) P. Kumm. (1871) cultivated on spent oyster substrate mixed with wheat straw (1:1, w/w mixture). The product was applied in different doses (C₁: 3 g kg⁻¹ and C₂: 5 g kg⁻¹) at three distinct timings (t₁: at spawning, t₂: after first harvest, t₃: at spawning and after first harvest). Protein and fiber contents increased respectively by 0.64 and 0.2% in C₁t₁ and by 0.46 and 0.8% in C₂t₂ compared to control (C₀t₀). Total carbohydrates increased by 0.48–3.76%. Sucrose and glucose contents decreased in the majority of treatments, while fructose increased in C₂t₁ (by 0.045%). Essential amino acids were the highest in C₁t₁, wherein respective improvement of 0.31, 0.10, 0.05, 0.21, 0.18, and 0.09% compared to C₀t₀. Similarly, C₁t₁ was superior in non-essential amino acids. Potassium, sodium, calcium, iron, and copper contents decreased in all treatments, with minor exceptions, zinc decreased in C₁t₁ and C₂t₁, while nickel and lead increased in all treatments. Conclusively, despite important ameliorations in the mushroom nutritional value, mostly in C₁t₁, the product should be further tested in lower doses (< 3 g kg⁻¹) to counteract its effect on heavy metal bioaccumulation.

The capacity of Pleurotus ostreatus to degrade the lignocellulose of spent coffee grounds (SCG) and its resultant nutrient composition is not yet studied. The study tested four SCG/wheat straw mixtures, containing 0, 33, 67, or 100% SCG. Initial lignin content was higher, and lignin loss was lower in mixtures containing SCG, compared to control revealing lower substrate degradation. Biological yield was negatively correlated with initial lignin content, and positively with the lignin loss from substrates. The nutritional value of mushrooms was improved by a general increase in carbohydrates, a decrease in sodium content with 33% and 67% SCG, and lower fat content with 33% SCG. Polyunsaturated fatty acids of mushrooms (PUFA) increased with 67% SCG; while saturated ones (SFA) increased with 33 and 67% SCG. All mushrooms had a close PUFA/SFA, ranging between 7.4 and 8.1. The study suggests using SCG as a nutritional supplement to the commercial wheat straw. Graphical abstract

Supplementation of the spent oyster substrate enhances its nutritional properties to produce a new mushroom cropping cycle. The study investigated the potential of a nano-fertilizer (Lithovit^®-Amino25) with an admixture of 25% l-amino acids on Pleurotus ostreatus production, proteins, and amino acid contents. The product applied at spawning (t1), after the first harvest (t2), and at both timings (t3), in two doses: 3 g/kg (C1) or 5 g/kg (C2). Compared with control (C0t0), the first harvest was earlier by 2.3–3.3 days in C1t1 and C2t1. The biological yield of the second harvest was improved by 28.0% in C2t2. Superior results were in C1t3 where the number of crops increased to four, biological efficiency was optimized (117.3%) at the third harvest, and biological and economic yields increased by 36.7% and 36.4%, respectively. Lignin was the most degraded in C1t3, while residual cellulose, hemicellulose, neutral detergent fiber, and acid detergent fiber were higher in all treated substrates than in control. In C2t1, mushrooms were the richest in proteins, while in C1t1, they were the richest in the essential amino acids threonine, valine, isoleucine, leucine, and histidine. Lithovit^®-Amino25 has a high potential for use in P. ostreatus production.

In several Mediterranean countries, olive pruning residues (OLPRs) are abandoned or burned leading to several environmental problems. Valorization of these agrowastes could be a challenge for the primary decomposer Pleurotus ostreatus, turning them into edible biomass. The OLPR was used alone (OLPR), or in mixtures with wheat straw (WS : OLPR 1 : 3 v/v and WS : OLPR 3 : 1 v/v). Mycelial colonization was hastened by 3.7 days in WS : OLPR 1 : 3 (v/v). Yields were comparable to control (WS) in WS : OLPR 3 : 1 (v/v). Organic matter loss decreased with increasing proportions of OLPR in substrates. The nutritional value of mushrooms was improved by lower fat and sodium contents, in WS : OLPR 1 : 3 (v/v) and WS : OLPR 3 : 1 (v/v), and higher total protein, crude fiber, iron, and total carbohydrates contents in WS : OLPR 3 : 1 (v/v), compared with those of control. Polyunsaturated fatty acids, mainly linoleic acid, were the most abundant in mushrooms. Monounsaturated fatty acids increased in mushrooms of the substrates containing OLPR. A good predictive model of partial least square regression analysis showed different relationships of mushroom palmitic, oleic, linolenic, palmitoleic, and stearic acids with substrate composition. Findings suggested the use of OLPR as a supplement to commercial wheat straw and as a tool to reduce the negative impacts of their hazardous disposal on the environment.