Properties of modified chitosan-based films and coatings and their application in the preservation of edible mushrooms: A review.

Edible mushrooms are prone to deteriorate during storage. A Single chitosan film or coating has limitations in preservation. Therefore, this article focused on the improvement of modified chitosan-based films and coatings on properties related to storage quality of edible mushrooms (e.g.: safety, barrier, mechanical, antioxidant and antibacterial properties). Besides, the application of chitosan-based materials in the preservation of mushrooms was also discussed. The modified chitosan film and coating can slow down the respiration of mushrooms, inhibit the growth of microorganisms, protect antioxidant compositions, and regulate the activity of related enzymes, thus improving the quality and prolonging the shelf life of mushrooms. Meanwhile, the added ingredients improve the water and gas barrier properties of chitosan through volume and group occupation, and reduce the light transmittance of chitosan through light transmission, scattering and absorption. Essential oils and polyphenolic compounds had a better enhancement of antioxidant and antimicrobial properties of chitosan.

Effect of Different Cooking Methods on the Bioactive Components, Color, Texture, Microstructure, and Volatiles of Shiitake Mushrooms.

The effects of different cooking methods (steaming, boiling, air frying, and oven baking) and cooking times (0, 5, 10, 15, and 20 min) on the bioactive components (total phenol, total flavonoid, crude polysaccharides, and eritadenine), color, texture, microstructure, and volatiles in shiitake mushrooms were investigated in this study. Steaming, boiling, and air frying for 5-20 min could decrease the contents of all the four bioactive components in the shiitake mushroom. However, oven baking for 5 min and 10 min showed the highest contents of total phenolics and total flavonoids, respectively. Moreover, the lowest losses of crude polysaccharides and eritadenine were observed for oven baking for 5 min and 15 min, respectively. The lightness of shiitake mushrooms was decreased by all treatments; however, steaming could keep a higher brightness compared with other methods. The microstructure was damaged by all cooking methods, especially air frying for 20 min. Meanwhile, steaming for 20 min decreased the hardness mostly, and there was no significant difference with air frying for 20 min. All cooking treatments decreased the complexity of the flavors and the relative contents of volatile compounds; the lowest contents were found when boiling for 5 min. From these results it can be seen that the physical, histological, and chemical features in shiitake mushroom were influenced by cooking methods and times. In addition, our results provide valuable information for the cooking and processing of shiitake mushrooms and other fungi.

Mycelial biomass and intracellular polysaccharides production, characterization, and activities in Auricularia auricula-judae cultured with different carbon sources.

The carbon source, an essential factor for submerged culture, affects fungal polysaccharides production, structures, and activities. This study investigated the impact of carbon sources, including glucose, fructose, sucrose, and mannose, on mycelial biomass and the production, structural characterization, and bioactivities of intracellular polysaccharides (IPS) produced by submerged culture of Auricularia auricula-judae. Results showed that mycelial biomass and IPS production varied with different carbon sources, where using glucose as the carbon source produced the highest mycelial biomass (17.22 ± 0.29 g/L) and IPS (1.62 ± 0.04 g/L). Additionally, carbon sources were found to affect the molecular weight (Mw) distributions, monosaccharide compositions, structural characterization, and activities of IPSs. IPS produced with glucose as the carbon source exhibited the best in vitro antioxidant activities and had the strongest protection against alloxan-damaged islet cells. Correlation analysis revealed that Mw correlated positively with mycelial biomass (r = 0.97) and IPS yield (r = 1.00), while IPS antioxidant activities correlated positively with Mw and negatively with mannose content; the protective activity of IPS was positively related to its reducing power. These findings indicate a critical structure-function relationship for IPS and lay the foundation for utilizing liquid-fermented A. aruicula-judae mycelia and the IPS in functional food production.

Phenolic profile, antioxidation and anti-proliferation activity of phenolic-rich extracts from Sanghuangporusvaninii.

In this study, phenolic-rich extracts from Sanghuangporus vaninii (SHE) were prepared, the phenolic profile and main phenolic compound content of SHE were studied by UPLC-Orbitrap-MS, and the antioxidant and antiproliferation activities of SHE were evaluated. The results showed that the total polyphenol content and the total flavonoid content of SHE were 42.420 ± 0.011 mg GAE/g EW and 8.504 ± 0.205 mg RE/g EW, respectively. Moreover, 14 phenolic acids and 8 flavonoids in SHE were identified, among which, the major polyphenols were protocatechualdehyde (394.68 µg/g), protocatechuic acid (196.88 µg/g), caffeic acid (96.11 µg/g), L-phenylalanine (12.72 µg/g) and (+)-taxifolin (8.59 µg/g). SHE showed strong radical scavenging, anti-lipid peroxidation and anti-DNA damage capacity in vitro. SHE could effectively induce HepG2 cell apoptosis via the caspases-dependent mitochondrial apoptotic pathway and arrest the cell cycle in the G0/G1 phase. The present study suggested that S. vaninii could be a valuable source of natural antioxidative and antiproliferative ingredients.

The physicochemical, antioxidant, hypoglycemic and prebiotic properties of γ-irradiated polysaccharides extracted from Lentinula edodes.

In this study, the influence of γ-irradiation with different dose (0, 4, 8, and 16 kGy) on chemical composition, physicochemical features and bioactivities of polysaccharides extracted from Lentinula edodes (LEP) were investigated. The carbohydrate content (from 59.47 to 70.96%), the solubility, the ⋅OH and DPPH scavenging ability of LEP increased with the increased γ-irradiation dose, while the protein content, the weight-average and number-average molecular weight of LEP were significantly decreased with the increased γ-irradiation dose. Moreover, γ-irradiation treatment caused LEP color changes and surface topography destroyed. γ-Irradiated LEP showed higher hypoglycemic activities in vitro than that of non-irradiated LEP. Moreover, γ-irradiated LEP had better proliferation promoting effects on Lactobacillus rhamnosus and L. plantarum. These results showed that γ-irradiation treatment changes the physicochemical features of LEP, thus affects its antioxidant, hypoglycemic and prebiotic properties, which suggests that γ-irradiated LEP has potential application in the pharmaceutical industries and functional foods. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-022-01234-5.

Transcriptome analysis provides insight into gamma irradiation delaying quality deterioration of postharvest Lentinula edodes during cold storage.

To better determine how gamma irradiation (GI) improves abiotic stress resistance, a transcriptome analysis of postharvest L. edodes in response to 1.0 kGy GI was conducted, and further the underlying mechanism of GI in delaying quality deterioration over 20 d of cold storage was explored. The results suggested that GI was involved in multiple metabolic processes in irradiated postharvest L. edodes. In comparison with the control group, the GI group contained 430 differentially expressed genes, including 151 upregulated genes and 279 downregulated genes, which unveiled characteristic expression profiles and pathways. The genes involved in the pentose phosphate pathway were mainly upregulated and the expression level of the gene encoding deoxy-D-gluconate 3-dehydrogenase was 9.151-fold higher. In contrast, the genes related to other energy metabolism pathways were downregulated. Concurrently, GI inhibited the expression of genes associated with delta 9-fatty acid desaturase, ribosomes, and HSP20; thus, GI helped postpone the degradation of lipid components, suppress transcriptional metabolism and regulate the stress response. Additionally, the metabolic behavior of DNA repair induced by GI intensified by noticeable upregulation. These regulatory effects could play a potential and nonnegligible role in delaying the deterioration of L. edodes quality. The results provide new information on the regulatory mechanism of postharvest L. edodes when subjected to 1.0 kGy GI during cold storage.

Gastrointestinal digestion, probiotic fermentation behaviors and immunomodulatory effects of polysaccharides from Sanghuangporus vaninii.

In this study, the crude polysaccharides (CSVP) and the preliminary purified polysaccharides (PSVP) from Sanghuangporus vaninii were obtained. The physicochemical properties, gastrointestinal digestion, and probiotic fermentation behaviors of CSVP and PSVP as well as the immunomodulatory effects of PSVP in cyclophosphamide-treated mice were investigated. The results showed that PSVP had higher total polysaccharides content and solubility, but lower radical scavenging activity than CSVP. Moreover, PSVP showed lower hydrolysis degree and better probiotic effects than CSVP. In immunosuppression mice model, PSVP supplement increased the body weight, spleen and thymus index, improved the release of cytokines IFN-γ, immunoglobulins IgM and IgG, and enhanced the lysozyme activity. Moreover, PSVP supplement significantly prevented the oxidative stress in vivo, increased the level of beneficial gut microbiota, especially Bacteroidaceae and Lactobscillsceae, as well as the content of short-chain fatty acids (SCFAs). These results indicated that PSVP could recover the immune response in cyclophosphamide-treated mice by regulating gut microbiota and intestinal barrier. The findings will lay a theoretical foundation for equitable utilization of S. vaninii resources as well as the product development.

Physicochemical Properties and Antioxidant Activity of Natural Melanin Extracted from the Wild Wood Ear Mushroom, Auricularia auricula (Agaricomycetes).

In this study, melanin from wild Auricularia auricula (WAA) was isolated using an ultra-high pressure (UHP)-assisted extraction method, and the physicochemical properties and antioxidant activity of WAA melanin were investigated. Under the optimized extraction conditions of a solid/liquid ratio of 1:30, a UHP of 450 MPa, a 22-min pressure holding time, a 1-mol/L NaOH concentration, and acid precipitation for 8 h, the WAA melanin extraction yield was 7.9 ± 0.16%. Moreover, the results showed that the surface of WAA melanin lacked structural order. Most melanin showed an average diameter of 1000 nm. WAA melanin had strong absorption at a wavelength of 210 nm and displayed typical characteristic absorption peaks. Moreover, WAA melanin contained 48.51% C, 6.88% H, 5.26% N, 0.45% S, and 38.90% O and may be a 3,4-dihydroxyphenylalanine melanin. An analysis of physicochemical properties showed that WAA melanin had good stability toward heat, light, and low concentrations of reducing agents and oxidizing agents. Furthermore, WAA melanin presented certain free radical scavenging activity. This study demonstrates that wild A. auricula melanin may have potential applications in the cosmetic or food industries as a natural antioxidant.

Differences of gut microbiota composition in mice supplied with polysaccharides from γ-irradiated and non-irradiated Schizophyllum commune.

In this study, polysaccharides from normal (N-SFP) and γ-irradiated (I-SFP) Schizophyllum commune were supplied to Kunming mice for 30 days. The results showed that N-SFP and I-SFP supplementation prevent body weight gain, enhance kidney uric acid metabolism and increase the concentration of SCFAs to a certain extent. Moreover, N-SFP and I-SFP promote the growth of beneficial gut microbiota and inhibit the growth of harmful bacteria. Compared to N-SFP, I-SFP decreased the relative abundance of Muribaculaceae and Lactobacillaceae, and increased the beneficial gut microbiota, especially the family of Akkermansiaceae, Lachnospiraceae and Bacteroidaceae. In total, I-SFP showed better effects than N-SFP in preventing weight gain, and modulating the mice gut microbiota, which suggests that I-SFP could act as a potential health supplement in the prevention of obesity.

Effects of ultrasound and gamma irradiation on quality maintenance of fresh Lentinula edodes during cold storage.

Microbial infection, senescence and water losses result in serious quality deterioration of postharvest mushrooms. The aim of this study was to investigate the impact of ultrasound treatment (US), gamma irradiation treatment (GI) and their combination on quality maintenance of fresh Lentinula edodes during storage. The results showed that US + GI was the most effective approach to maintaining the quality of mushrooms. US + GI reduced natural microflora present on L. edodes, such as total number of colonies, molds, yeasts, Pseudomonas and Enterobacteriaceae. Furthermore, US + GI stimulated phenylalanine ammonia lyase, maintained the highest level of total phenolic content (733.63 mg GAE/kg on Day 4), and postponed the occurrence of reduced ascorbic acid (33.7% retention relative to the control), which contributed to strengthening the antioxidant capacity. Additionally, US + GI retarded water mobility and loss. In brief, the US + GI in this study is an effective hurdle technology for preserving the quality of fresh L. edodes during storage.

Evaluation of In Vitro Antioxidant and Antihyperglycemic Activities of Extracts from the Lion's Mane Medicinal Mushroom, Hericium erinaceus (Agaricomycetes).

To obtain activated fractions, the ethanol extract (EE) of Hericium erinaceus was fractionated to get petroleum ether fraction (PEF), chloroform fraction (CF), ethyl acetate fraction (EAF) and n-butanol fraction (NF). Total phenol content (TPC) and total flavonoid content (TFC) in the fractions were determined, and the phenolic compounds were characterized and quantitated using liquid chromatography-electrospray ionization-mass spectrometry. Meanwhile, in vitro antioxidant and antihyperglycemic activities of extracts were evaluated respectively based on their 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging abilities as well as α-amylase and α-glucosidase inhibitory abilities. Finally, the inhibition modes of extracts on α-amylase and α-glucosidase were detected by kinetic assay. The results showed that TPC, TFC, and the content of phenolic compounds in the extracts were different. EAF contained the highest contents of both TPC and TFC and exhibited strongest inhibitory effects on α-amylase and α-glucosidase, with half maximal inhibitory concentration (IC50) values of 0.47 ± 0.02 and 0.63 ± 0.01 mg/mL, respectively. However, CF showed the highest scavenging abilities on DPPH and ABTS radicals, with IC50 values of 2.30 ± 0.12 and 1.72 ± 0.06 mg/mL, respectively. Correlation analysis showed that the high antihyperglycemic ability of EAF may be related to ferulic acid, whereas cinnamic acid may be responsible for the high antioxidant ability of CF. Furthermore, all fractions were found to exert inhibition on α-amylase and α-glucosidase in mixed-type and competitive manners, respectively. Overall, these results suggest that H. erinaceus has a potential effect on antihyperglycemic and antioxidant activity.

The Impact of Mushroom Polysaccharides on Gut Microbiota and Its Beneficial Effects to Host: A Review.

Mushroom polysaccharides are a type of bioactive macromolecular which isolated from fruiting bodies, mycelia or fermentation broths of edible or medicinal fungus. Recently, mushroom polysaccharides have attracted a lot of attention for regulating gut microbiota via reducing the levels of pathogens and stimulating the growth of beneficial microorganisms, thus creating new possibilities for their use in nutraceutical and functional foods industries. The current review summarizes the isolation, purification and structural characterization methods of mushroom polysaccharides, the degradation of mushroom polysaccharides in intestine, the impacts of mushroom polysaccharides on gut microbiota community and short chain fatty acids (SCFAs) productivity, and the beneficial effects of mushroom polysaccharides to host by targeting gut microbiota. We hope this article can offer some theoretical bases and inspirations for the mechanism study of the bioactivity of mushroom polysaccharides.

Optimization of Fermentation Process and Its Impact on Gene Transcription of Intracellular Polysaccharide Synthesis in the Wood Ear Medicinal Mushroom Auricularia auricula-judae (Agaricomycetes).

To improve the production of mycelial biomass and intracellular polysaccharide (IPS), the culture medium composition and culture condition were respectively optimized by response surface methodology and one-factor-at-a-time methodology. The impact of fermentation process on the transcription of genes involved in IPS synthesis was evaluated using quantitative reverse transcription PCR (qRT-PCR). The yield of biomass and IPS were increased by 150% and 177% under the optimized fermentation process, respectively. Moreover, the optimization of fermentation process significantly increased the transcription of genes involved in IPS synthesis, especially pgm-1, ugp, and pgi. This is the first exploration of gene transcription profile for IPS synthesis of Auricularia auricula-judae under submerged fermentation. These results could provide a potential tool for fermentation process optimization and transcriptional regulation of IPS biosynthesis in A. auricula-judae.

Influence of high hydrostatic pressure pretreatment on properties of vacuum-freeze dried strawberry slices.

Effects of high hydrostatic pressure (HHP) (50, 100, 150, 200 and 250 MPa) pretreatment on water mobility and distribution, drying duration, microstructure, color, cell wall fraction and tissue structure of strawberry slices were investigated. HHP significantly increased water mobility of the strawberry slices, resulting in the reduction of drying duration by 9-24%. As the pretreatment pressure was increased, redness value and anthocyanin content continuously increased, soluble pectin (SBP) content increased and then decreased, while the contents of protopectin (PTP) and cellulose decreased. After the HHP pretreatment, chromoplasts and moisture was distributed more uniformly in the strawberry slices. Microscopy images showed the formation of microscopic holes or channels in the matrix and the breakdown of tissue structure by HHP. Results suggested HHP pretreatment disrupted the integrity of the fresh strawberry which enhanced the drying efficiency and migration of the chromoplasts during the vacuum-freeze drying process.

Effects of ultrahigh pressure and ultrasound pretreatments on properties of strawberry chips prepared by vacuum-freeze drying.

The present work investigated the influences of ultrahigh pressure (UHP), ultrasound (US) and their combination (UHP-US) as pretreatments on properties of vacuum-freeze dried strawberry slices. During vacuum-freeze drying, drying duration and total energy consumption of UHP sample, US sample and UHP-US sample was decreased. After the UHP or US pretreatments, a* value (redness), antioxidative substances (total anthocyanin content, total flavonoid content, total phenolic content, diphenyl picrylhydrazyl (DPPH), hydroxyl (-OH) radical-scavenging assay), hardness and cross-section areas of matrix in the dried slices were significantly (P < 0.05) increased. Transverse relaxation times and peak area corresponding to free water in the pretreated samples were obviously decreased, indicating lower mobility in the pretreated samples. As compared with UHP or US individually, UHP in combination with US increased those parameters more pronouncedly. Therefore, UHP and US are promising techniques for the vacuum-freeze drying processing of strawberry products.

Characterization of physicochemical and biological properties of Schizophyllum commune polysaccharide extracted with different methods.

Water-soluble polysaccharides from Schizophyllum commune (SPGs) were extracted using different methods including hot-water extraction (HWE), ultrasound-assisted extraction (UE), microwave-assisted extraction (ME) and high pressure extraction (HPE). The physicochemical characteristics, antioxidant activity and hypoglycemic activity of four different SPGs were investigated. The results indicated that the polysaccharides yield (8.26%), uronic acid content (3.0%), total polysaccharides content (67.96%) and molecular weight (52.7 kDa) of SPGs extracted by HWE were higher than those obtained by other methods. FT-IR spectra and conformation information of four SPGs were similar, however, the color characteristics, the monosaccharide species and molar ratios, the solubility and micro-structure of each SPGs were significantly different. Though the molecular weight (11.0 kDa) of UE-SPGs was lowest, it showed the highest antioxidant activity and hypoglycemic activity. It could be considered that the UE extraction method might be a good potential extraction technique for the SPGs with high bioactivities.

Identification and characterization of a novel light-induced promoter for recombinant protein production in Pleurotus ostreatus.

A lectin gene (plectin) with a high level of expression was previously identified by comparative transcriptome analysis of Pleurotus ostreatus. In this study, we cloned a 733-bp DNA fragment from the start codon of the plectin gene. Sequence analysis showed that the plectin promoter (Plp) region contained several eukaryotic transcription factor binding motifs, such as the TATA-box, four possible CAAT-box, light respon-siveness motifs and MeJA-responsiveness motifs. To deter-mine whether the Plp promoter was a light-regulated promoter, we constructed an expression vector with the fused egfp-hph fragment under the control of the Plp promoter and transformed P. ostreatus mycelia via Agrobacterium tunte-faciens. PCR and Southern blot analyses confirmed the Plp-egfp-hph fragment was integrated into the chromosomal DNA of transformants. qRT-PCR, egfp visualization, and intracellular egfp determination experiments showed the Plp promoter could be a light-induced promoter that may be suitable for P. ostreatus genetic engineering. This study lays the foundation for gene homologous expression in P. ostreatus.

Remediation and Mechanisms of Cadmium Biosorption by a Cadmium-Binding Protein from Lentinula edodes.

Cadmium bioremediation with metal-binding proteins is primarily conducted using metallothioneins (MTs). However, in the present study, we investigated a non-MT cadmium-binding protein from Lentinula edodes (LECBP) as a remediation tool for cadmium biosorption in Escherichia coli. The results indicated that the expression of LECBP significantly enhanced the cadmium biosorption capacity of transgenic E. coli. The secondary structure and conformation of LECBP were changed after binding with cadmium as evidenced by circular dichroism and fluorescence spectroscopy. The results of Fourier transform infrared spectroscopy indicated that carboxyl oxygen and amino nitrogen atoms were involved in the interaction between LECBP and cadmium. The results further demonstrated that glutamic acid and histidine residues are the potential binding sites. Our results have thus provided new insights into cadmium bioremediation in an aquatic environment.

Purification and Characterization of a Cadmium-Binding Protein from Lentinula edodes.

Many organisms possess the ability to produce metal-binding proteins to absorb cadmium. Metallothioneins, an important family of cysteine-rich metal-binding proteins, have been isolated and well characterized. However, Lentinula edodes may have a different type of cadmium-binding protein that contains fewer cysteine residues. In the present study, we purified a cadmium-binding protein from L. edodes (LECBP) by gel filtration and anion exchange chromatography and then identified LECBP by LC-MS/MS. We found LECBP to be a novel cadmium-binding protein, which contained 220 amino acid residues but no cysteine residue. LECBP had a high binding affinity for Cd(II) with a Kd value of 97.3 µM. The percentages of α-helix, ß-sheet, ß-turn, and random coil in LECBP were 15.7%, 39.4%, 8.0%, and 37.1%, respectively. In addition, high temperatures and an acidic environment influenced the conformation of LECBP. Our results will thus provide a new perspective to understand the mechanism of cadmium accumulation in L. edodes.

The Antioxidant Properties, Tyrosinase and α-Glucosidase Inhibitory Activities of Phenolic Compounds in Different Extracts from the Golden Oyster Mushroom, Pleurotus citrinopileatus (Agaricomycetes).

In this study, phenolic compounds that graded prepared from Pleurotus citrinopileatus using different solvents were obtained. The total content of phenolic and flavonoid, the phenolic profiles, the antioxidant activities, the tyrosinase, and α-glucosidase inhibitory activities of different extracts were determined. The results showed the phenolic and flavonoid content in different extracts ranging from 0.188 to 2.677 mg GAE/g DW and 0.137 to 0.445 mg QE/g DW, respectively. Six phenolic compounds were identified in different extracts by HPLC and the content range from 0.48 to 5778.59 µg/g DW. The water extracts showed strong scavenging activity of radicals and tyrosinase inhibitory activity, whereas acetone extracts showed obvious reducing power and high α-glucosidase inhibitory activity. These findings confirm that the P. citrinopileatus mushroom is a potential natural source of antioxidants for use in food and medicine industries along with their possible applications in ant-melanin and antidiabetic applications.