Phenotypic analysis has significant potential for aiding breeding efforts. However, there is a notable lack of studies utilizing phenotypic analysis in the field of edible fungi. Pleurotus geesteranus is a lucrative edible fungus with significant market demand and substantial industrial output, and early-stage phenotypic analysis of Pleurotus geesteranus is imperative during its breeding process. This study utilizes image recognition technology to investigate the phenotypic features of the mycelium of P. geesteranus. We aim to establish the relations between these phenotypic characteristics and mycelial quality. Four groups of mycelia, namely, the non-degraded and degraded mycelium and the 5th and 14th subcultures, are used as image sources. Two categories of phenotypic metrics, outline and texture, are quantitatively calculated and analyzed. In the outline features of the mycelium, five indexes, namely, mycelial perimeter, radius, area, growth rate, and change speed, are proposed to demonstrate mycelial growth. In the texture features of the mycelium, five indexes, namely, mycelial coverage, roundness, groove depth, density, and density change, are studied to analyze the phenotypic characteristics of the mycelium. Moreover, we also compared the cellulase and laccase activities of the mycelium and found that cellulase level was consistent with the phenotypic indices of the mycelium, which further verified the accuracy of digital image processing technology in analyzing the phenotypic characteristics of the mycelium. The results indicate that there are significant differences in these 10 phenotypic characteristic indices ( P < 0.001 ), elucidating a close relationship between phenotypic characteristics and mycelial quality. This conclusion facilitates rapid and accurate strain selection in the early breeding stage of P. geesteranus.

Long-term high salt intake exerts a negative impact on human health. The excessive use of sodium substitutes in the food industry can lead to decreased sensory quality of food. γ-Glutamyl peptides with pronounced taste-enhancing effects can offer an alternative approach to salt reduction. However, the content and yield of γ-glutamyl peptides in natural foods are relatively low. Enzyme-catalyzed synthesis of γ-glutamyl peptides provides a feasible solution. In this study, Pleurotus geesteranus was hydrolyzed by Flavourzyme to generate protein hydrolysates. Subsequently, they were modified by Bacillus amyloliquefaciens γ-glutamyl transpeptidase to generate γ-glutamyl peptides. The reaction conditions were optimized and their taste-enhancing effects were evaluated. Their peptide sequences were identified by parallel reaction monitoring with liquid chromatography-tandem mass spectrometry and analyzed using molecular docking. The optimal conditions for generation of γ-glutamyl peptides were a pH of 10.0, an enzyme condition of 1.2 U/g, and a reaction time of 2 h, which can elicit a strong kokumi taste. Notably, it exhibited a remarkable taste-enhancing effect for umami intensity (76.07%) and saltiness intensity (1.23-fold). Several novel γ-glutamyl peptide sequences were found by liquid chromatography-tandem mass spectrometry, whereas the binding to the calcium-sensing receptor was confirmed by molecular docking analysis. Overall, γ-glutamyl peptides from P. geesteranus could significantly enhance the umami and salt tastes, which can serve as promising taste enhancers.

A water-soluble glucomannogalactan was isolated from P. geesteranus fruit bodies by hot water extraction and column chromatography method. The structure, chain conformation and immune effect of PGP-1c (20.9 kDa) were investigated comprehensively based on high purity and neutral sugar content (94.7 ± 0.5%). Confirmed by monosaccharide composition, methylation and NMR analysis, PGP-1c was composed of unsubstituted (1,6-α-Gal and 1,6-α-3-OMe-Gal) and monosubstituted (1,2,6-α-Gal and 1,2,6-α-3-OMe-Gal) galactose units in the backbone through α-(1 → 6) glycosidic bonds and the possible branches that a long-branched chain composed of →3)-Glc-(1 → Man and a few fucoses were connected at the O-2 of galactose with a branching degree of 48%. Through the conformational behavior of the molecular chain, it was observed that PGP-1c might have a long-branched or stacked macromolecular network caused by O-CH3 groups. Moreover, PGP-1c could promote the secretion of NO and cytokines significantly in a dose-dependent manner, which indicated a good immune-enhancing effect.

Pleurotus geesteranus is a promising source of bioactive compounds. However, knowledge of the antioxidant behaviors of P. geesteranus protein hydrolysates (PGPHs) is limited. In this study, PGPHs were prepared with papain, alcalase, flavourzyme, pepsin, and pancreatin, respectively. The antioxidant properties and cytoprotective effects against oxidative stress of PGPHs were investigated using different chemical assays and H2O2 damaged PC12 cells, respectively. The results showed that PGPHs exhibited superior antioxidant activity. Especially, hydrolysate generated by alcalase displayed the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (91.62%), 2,2-azino-bis (3-ethylbenzothia zoline-6-sulfonic acid) (ABTS) radical scavenging activity (90.53%), ferric reducing antioxidant power, and metal ion-chelating activity (82.16%). Analysis of amino acid composition revealed that this hydrolysate was rich in hydrophobic, negatively charged, and aromatic amino acids, contributing to its superior antioxidant properties. Additionally, alcalase hydrolysate showed cytoprotective effects on H2O2-induced oxidative stress in PC12 cells via diminishing intracellular reactive oxygen species (ROS) accumulation by stimulating antioxidant enzyme activities. Taken together, alcalase hydrolysate of P. geesteranus protein can be used as beneficial ingredients with antioxidant properties and protective effects against ROS-mediated oxidative stress.

The present work investigated the anti-inflammatory, antioxidant, and lung protection effects of acetylated Pleurotus geesteranus polysaccharides (AcPPS) on acute lung injury (ALI) mice. The acetylation of AcPPS was successfully shown by the peaks of 1737 cm-1 and 1249 cm-1 by FTIR. The animal experiments demonstrated that lung damage can be induced by zymosan. However, the supplementation of AcPPS had potential effects on reducing lung index, remitting inflammatory symptoms (TNF-α, IL-1β, and IL-6), inhibiting NF-κB signal pathway based on up-regulating the level of IκBα and down-regulating p-IκBα level by Western blotting and immunofluorescence assay, preventing oxidative stress (ROS, SOD, GSH-Px, CAT, T-AOC, and MDA), reducing lipid accumulation (TC, TG, LDL-C, HDL-C, and VLDL-C), and alleviating lung functions by histopathologic observation. These results demonstrated that AcPPS might be suitable for natural food for prevention or remission in ALI.

Pleurotus geesteranus has recently been gaining popularity due to its strong umami taste. In the present study, umami taste, energy level, and energy metabolism-related enzymes activity in harvested P. geesteranus, stored at 20, 10, 5, and 0 °C, were investigated to evaluate the relationship between umami taste and energy status. Results showed that the mushroom at 5 °C exhibited significantly higher (p < 0.05) equivalent umami concentration (EUC), higher content of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and higher activity of succinic dehydrogenase (SDH) and cytochrome c oxidase (CCO) in late storage. AMP, associating umami taste with energy, presented a significantly positive correlation with EUC and umami determined by electronic tongue at 5 °C. Furthermore, there were better correlations between umami taste and energy status of mushroom at 5 °C. The results suggest that higher energy status of post-harvest P. geesteranus contributes to better umami taste.