Investigation the nutritional properties of Auricularia auricula pulp fermented with Lactobacillus strains and their effects on gut microbiota

BACKGROUND

Auricularia auricula is rich in bioactive components, and microbial fermentation can further dramatically increase its content and bioavailability. However, there are few studies on the relationship between fermented A. auricula pulp (FAAP) and gut microbiota. In this study, standard strains Lactobacillus plantarum 21801 and 21805 purchased from the China Center of Industrial Culture Collection were used to ferment A. auricula pulp at a ratio of 2:1, with an inoculum of 5%, a fermentation temperature of 31 °C, and a fermentation time of 22 h. The nutritional properties, aroma, and color of FAAP and their effects on the body characteristics of mice and the structure and abundance of gut microbiota are discussed.

RESULTS

The results showed that, compared with A. auricula pulp, FAAP significantly increased the nutritional properties while maintaining favorable sensory quality and flavor profiles. Among them, the content of total polyphenols and total flavonoids reached 22.04 μg mL-1 and 20.56 μg mL-1 respectively, and the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid free-radical scavenging rate increased to 73.21%. The consumption of FAAP had no negative effects on weight or liver and kidney function in mice and dramatically enhanced the antioxidant capacity in the liver and serum. The production of short-chain fatty acids in the gut was promoted, the relative abundance of beneficial bacteria (Lactobacillus, Bifidobacterium, norank_f__Muribaculaceae and unclassified_f__Lachnospiraceae) increased, and the growth of some pathogenic bacteria (Helicobacter, Mucispirillum, and Alloprevotella) was inhibited.

CONCLUSION

These findings demonstrate that FAAP is rich in nutrients and has unique functional properties that promote host health and regulate the gut microbiota. © 2023 Society of Chemical Industry.

Characterization and biological activities of polysaccharides extracted from Auricularia auricula with different extraction methods

Polysaccharides derived from Auricularia auricula exhibit diverse biological activities and hold significant potential for commercial utilization as functional food ingredients. In this investigation, polysaccharides from A. auricula were obtained using six extraction techniques (ammonium oxalate solution extraction, sodium hydroxide solution extraction, hot water extraction, pectinase and cellulase-assisted extraction, ultrasonic-assisted extraction, and microwave-assisted extraction). Subsequently, a comprehensive comparison was conducted to evaluate their physicochemical properties and biological functionalities. The ammonium oxalate solution extraction method yielded a higher extraction rate (11.76%) and polysaccharide content (84.12%), as well as a higher uronic acid content (10.13%). Although the six Auricularia polysaccharides had different molecular weight distributions, monosaccharide molar ratios, similar monosaccharide compositions, and characteristic functional groups of polysaccharides, they exhibited different surface morphology. In vitro assays showed that polysaccharides extracted by ammonium oxalate solution possessed good scavenging ability against DPPH free radical, hydroxyl free radical and superoxide anion free radical as well as reduction power of iron ion. At the same time, both polysaccharides extracted by ammonium oxalate solution and sodium hydroxide solution promoted NO production in mouse macrophages along with the secretion of cytokines TNF-α, IL-1β, and IL-6. These results indicated significant differences in the structure and characteristics among Auricularia polysaccharides prepared by various extraction methods, which may be related to the variety or origin of A. auricula; furthermore, their bioactivities varied accordingly in vitro assays where the ammonium oxalate solution extraction method was found more beneficial for obtaining high-quality bioactive Auricularia polysaccharides.

Auricularia auricula polysaccharides attenuate obesity in mice through gut commensal Papillibacter cinnamivorans

INTRODUCTION

Auricularia auricula is a well-known traditional edible and medical fungus with high nutritional and pharmacological values, as well as metabolic and immunoregulatory properties. Nondigestible fermentable polysaccharides are identified as primary bioactive constituents of Auricularia auricula extracts. However, the exact mechanisms underlying the effects of Auricularia auricula polysaccharides (AAP) on obesity and related metabolic endpoints, including the role of the gut microbiota, remain insufficiently understood.

METHODS

The effects of AAP on obesity were assessed within high-fat diet (HFD)-based mice through obesity trait analysis and metabolomic profiling. To determine the mechanistic role of the gut microbiota in observed anti-obesogenic effects AAP, faecal microbiota transplantation (FMT) and pseudo-germ-free mice model treated with antibiotics were also applied, together with 16S rRNA genomic-derived taxonomic profiling.

RESULTS

High-fat diet (HFD) murine exposure to AAP thwarted weight gains, reduced fat depositing and enhanced glucose tolerance, together with upregulating thermogenesis proteomic biomarkers within adipose tissue. Serum metabolome indicated these effects were associated with changes in fatty acid metabolism. Intestine-dwelling microbial population assessments discovered that AAP selectively enhanced Papillibacter cinnamivorans, a commensal bacterium with reduced presence in HFD mice. Notably, HFD mice treated with oral formulations of P. cinnamivorans attenuated obesity, which was linked to decreased intestinal lipid transportation and hepatic thermogenesis. Mechanistically, it was demonstrated that P. cinnamivorans regulated intestinal lipids metabolism and liver thermogenesis by reducing the proinflammatory response and gut permeability in a JAK-STAT signaling-related manner.

CONCLUSION

Datasets from the present study show that AAP thwarted dietary-driven obesity and metabolism-based disorders by regulating intestinal lipid transportation, a mechanism that is dependent on the gut commensal P. cinnamivorans. These results indicated AAP and P. cinnamivorans as newly identified pre- and probiotics that could serve as novel therapeutics against obesity.

The Current State and Future Prospects of Auricularia auricula's Polysaccharide Processing Technology Portfolio

Auricularia auricula polysaccharides (AAP) have been widely studied in the field of medicine and healthcare because of their unique structure and physiological activity. Many species of Auricularia auricula polysaccharides have been extracted, isolated, and purified by different methods, and their structures have been analyzed. Auricularia auricula polysaccharides have been proven to have beneficial effects on the human body, including slowing the aging process, controlling the intestinal system, and treating cardiovascular disorders. In this paper, the extraction, isolation, and purification of AAP from Auricularia auricula, as well as research in the field of medicine and healthcare, have pointed to the shortcomings and limitations of these methods. We also suggest future research directions for Auricularia auricula polysaccharides; standardized processing methods must be confirmed, and officially approved AAPs are needed for commercial applications. Finally, an optimistic outlook on the development of AAPs is given.

Enhancement of nutritional, sensory and storage stability by lactic fermentation of Auricularia auricula

BACKGROUND

Auricularia auricula is of important nutritional value, although its utilization or consumption are mainly under the original form with no further processing. Indeed, its liquid or other fermented products contribute to improved digestion and absorption of nutrients.

RESULTS

The present study used Lactiplantibacillus plantarum to ferment A. auricula juice after an initial processing comprising superfine grinding and high-pressure homogenization. The content of probiotic bacteria in the juice of A. auricula reached 8.48 log colony-forming units mL^-1 after 24 h of fermentation under 37 °C, with the addition of 3% carbon and 0.3% nitrogen source. Meanwhile, the antioxidant activity was increased approximately two-fold, as well as the enriched volatile flavors, both effectively cover up the unwelcoming earthy smell of A. auricula. Furthermore, the storage stability was also strengthened up to 28 days.

CONCLUSION

In summary, the introduced fermentation process not only realized the purpose of improving the nutritional value of A. auricula, but also effectively upgraded the sensory evaluation of A. auricula products. © 2022 Society of Chemical Industry.

Studies on the biosynthetic pathways of melanin in Auricularia auricula

Melanin is a natural pigment ubiquitously present in living organisms, including bacteria, fungi, plants, and animals. Melanin produced by the edible mushroom Auricularia auricula has a remarkable potential for resource development. Several A. auricula strains planted across China were collected and analyzed for mycelial growth rate and colony RGB value for color block. Further, the effects of various nutrients on melanin formation, including different carbon and nitrogen sources were evaluated to optimize medium for submerged fermentation. The pathways involved in the biosynthesis of melanin in A. auricula were investigated using an enzyme inhibitor assay and intermediate determination. In addition, the functional activity of purified A. auricula melanin was assessed. The highest melanin yield (1.797 g/L) was displayed by strain AU-3 in medium I. A. auricula melanin was composed of eumelanin, pheomelanin and 1,8-dihydroxynaphthalene melanin, and the biosynthetic pathways involved were Raper-Mason and 1,8-dihydroxynaphthalene melanin pathway. In addition, melanin purified from A. auricula exhibited substantial antioxidant, antibacterial, and antitumor activities. This article is protected by copyright. All rights reserved.

Delivery of Phenolic Compounds, Peptides and β-Glucan to the Gastrointestinal Tract by Incorporating Dietary Fibre-Rich Mushrooms into Sorghum Biscuits

Sorghum biscuits were enriched with mushroom powders (Lentinula edodes, Auricularia auricula and Tremella fuciformis) at 5%, 10% and 15% substitution levels. An in vitro gastrointestinal digestion was used to evaluate the effect of this enrichment on the phenolic content and soluble peptide content as well as antioxidant activities of the gastric or intestinal supernatants (bio-accessible fractions), and the remaining portions of phenolic compounds, antioxidants and β-glucan in the undigested residue (non-digestible fraction). The phenolic content of the gastric and intestinal supernatants obtained from digested mushroom-enriched biscuits was found to be higher than that of control biscuit, and the phenolic content was positively correlated to the antioxidant activities in each fraction (p < 0.001). L. edodes and T. fuciformis enrichment increased the soluble protein content (small peptide) of sorghum biscuits after in vitro digestion. All mushroom enrichment increased the total phenolic content and β-glucan content of the undigested residue and they were positively correlated (p < 0.001). The insoluble dietary fibre of biscuits was positively correlated with β-glucan content (p < 0.001) of undigested residue. These findings suggested that enriching food with mushroom derived dietary fibre increases the bioavailability of the non-digestible β-glucan and phenolic compounds.

Effects of Polysaccharides From Auricularia auricula on the Immuno-Stimulatory Activity and Gut Microbiota in Immunosuppressed Mice Induced by Cyclophosphamide

Recently, the immuno-enhancing potential of polysaccharide from Auricularia auricula (AAP) has been an area of research interest. However, the immune-stimulatory activity and mechanisms of AAP in immunosuppressive mice treated with cyclophosphamide (CTX) are still poorly understood. This study aimed to evaluate the immuno-enhancing effects of AAP and mine its possible mechanisms. Firstly, polysaccharides were isolated from A. auricula and purified. Secondly, the immune-stimulatory activities of the first AAP fraction (AAP1) were evaluated in the CTX-treated mice. Results showed that AAP1 significantly enhanced immune organ indexes, remarkably stimulated IFN-γ, IL-2, IL-4, IL-10, and TNF-α levels in the serum, and dramatically up-regulated the mRNA levels of Claudin-1, Occludin and ZO-1. Compared to the CTX group, AAP1 administration restored the gut microbiota composition similar to that of the control group by decreasing the ratio of Firmicutes/Bacteroidetes and increasing the relative abundances of short-chain fatty acid-producing microbiota. This study provides useful information for its further application as an immune-stimulator in foods and drugs.

Isolation, purification, characterization, and immunomodulatory effects of polysaccharide from Auricularia auricula on RAW264.7 macrophages

Auricularia auricula polysaccharide (AAP) was isolated by hot-water extraction and purified to evaluate its structural and immunomodulatory effects on RAW264.7 macrophages. The results show that three kinds of Auricularia auricula polysaccharides (c-AAP) were obtained and named as AAP-I, AAP-II, and AAP-III Their further purification found that AAP-I and AAP-II were glycoproteins, and only AAP-III was a pure polysaccharide, which we named AAP for further experiments. Structural characteristics revealed that AAP was a homogeneous galactan comprising mannose, rhamnose, gluconic acid, glucose, galactose, arabinose, and fucose in a molar ratio of 5.02:0.9:0.12:4.48:0.37:1.0:0.36, and the average molecular weight is approximately 23.51 kDa. Methylation analysis revealed that AAP mainly consisted of 1,4-linked-Glcp, 1,4,6-linked-Glcp, terminal Glcp, 1,4-linked-Manp, 1,2,6-linked-Manp, and terminal Arap. Furthermore, the in vitro immunomodulatory activities of AAP were evaluated by cell proliferation, NO production, and phagocytic ability using RAW264.7 macrophage cells. The results show that AAP not only promoted the activation of macrophages but also provided a scientific basis for the further use of AAP. PRACTICAL APPLICATIONS: Three water-soluble polysaccharides were extracted from Auricularia auricula of Changbai Mountain, two of which contained binding proteins. Determination of molecular weight, structure, and immunoreactivity of pure polysaccharide components. The result clearly demonstrated the benefits of this plant as a healthy functional food.

Effect of Auricularia auricula aqueous extract on survival of Lactobacillus acidophilus La-5 and Bifidobacterium bifidum Bb-12 and on sensorial and functional properties of synbiotic yogurt

The effect of Auricularia auricula aqueous extract (AAE) on the survival of Lactobacillus acidophilus La-5 and Bifidobacterium bifidum Bb-12, and on chemical and sensory properties of yogurt was investigated during 28 days of storage at 4°C. The use of 0.05% of AAE improved the survival of L. acidophilus La-5 and B. bifidum Bb-12 about 0.35 and 0.58 log CFU/g, respectively. However, AAE in 0.1% concentration enhanced the survival of L. acidophilus La-5 and B. bifidum Bb-12 about 0.43 and 0.51 log CFU/g, respectively. Moreover, 0.1% concentration of AAE drastically increased antioxidant activity and total phenolic content to 115.30 mg BHT eq./kg and 1,057.6 mg Gallic acid/kg after 28 days, respectively. Addition of AAE to the yogurt significantly decreased sensorial acceptance while increased syneresis compared to the control group (p < .05). In conclusion, the results of this study showed that addition of AAE improved probiotic protection and functional properties of the yogurt recommending its application in symbiotic yogurt.

Comprehensive utilization of edible mushroom Auricularia auricula waste residue-Extraction, physicochemical properties of melanin and its antioxidant activity

In order to promote the comprehensive utilization of the Auricularia auricula waste residue, the extraction process and the physicochemical properties of melanin from A. auricula waste residue were studied. Furthermore, the chemical antioxidant activity of waste residue melanin and its protective effect on cell oxidative injury induced by H2O2 were investigated. The results indicated that the ultrasonic-assisted extraction process could be used to extract the melanin from A. auricula waste residue. Melanin had a good solubility in alkali solution and exhibited a certain stability to thermal. There was no significant difference between A. auricula melanin control group and waste residue melanin on ABTS, DPPH, and hydroxyl radical scavenging activity. Waste residue melanin significantly inhibited the cell death caused by H2O2, and the cell viability was restored to 98.09 ± 5.97% when the melanin concentration was 1.6 mg/ml. Cell morphology observation confirmed that the melanin ameliorated the morphological changes of cells induced by oxidative stress.

Anti-Disuse Osteoporosis Activity of a Complex of Calcium-Binding Peptide from Auricularia auricula Protein Hydrolysates

Osteoporosis is a common metabolic bone disease that is often seen in bedridden patients and astronauts. Long-term bed rest and nonweight bearing tend to induce disuse osteoporosis. Calcium supplements are commonly used to help treat disuse osteoporosis along with medications, most of which are calcium carbonate based, but they have poor absorption effects. In this study, we prepared a novel Auricularia auricula peptide-calcium complex (AP-Ca) and evaluated its protective effects on disuse osteoporosis. In vitro assays showed that AP-Ca significantly increased the contents of calcium (P < 0.05) and the activity of alkaline phosphatase (AKP; P < 0.05) of osteoblasts cultured in a two-dimensional-rotating wall vessel. Meanwhile, supplementation with AP-Ca also inhibited the production of pro-inflammatory factors induced by the loss of stress, especially TNF-α (P < 0.05). In vivo, a mouse tail suspension (TS) model was established, and the results showed that AP-Ca helped to improve bone mineral density, bone mineral content, and bone organic content in TS mice and effectively alleviated the alteration of enzymes related to bone metabolism, including AKP (P < 0.05) and serum tartrate-resistant acid phosphatase (P < 0.05), to avoid more serious bone loss induced by TS. Furthermore, we found that AP-Ca downregulated the bone resorption-associated pro-inflammatory genes interleukin-1 (IL-1), tumor necrosis factor-α, and IL-6 by 59.53 ± 3.55%, 48.01 ± 5.68%, and 40.00 ± 5.89%, respectively (P < 0.05). In conclusion, AP-Ca showed potential to suppress bone loss induced by disuse and might be considered a new alternative to reduce the risk of disuse osteoporosis. PRACTICAL APPLICATION: This peptide-calcium complex supplement exhibited protective effects on the bone loss induced by disuse, which provided a new alternative for patients and astronauts to reduce the risk of disuse osteoporosis.

The effects of polysaccharides from Auricularia auricula (Huaier) in adjuvant anti-gastrointestinal cancer therapy: A systematic review and network meta-analysis

The aim of this study was to assess the comparative efficacy and safety of polysaccharides from Auricularia auricula (Huaier) for patients with gastrointestinal cancers (GICs) through a systematic review and network meta-analysis. We performed a network meta-analysis to identify evidence from clinical trials. We searched databases for publications up to February 2018. The prespecified primary efficacy outcomes were clinical therapeutic effects, which included the treatment response rate, 0.5-year overall survival rate, 1-year overall survival rate, 2-year overall survival rate, KPS improved rate and AFP decreased rate. The safety outcomes were the side effects of Huaier. The secondary efficacy outcome was immune function. Subgroup analyses and meta-regression were performed according to the various cancer types in all of the efficacy and safety outcomes. The study is registered with PROSPERO (CRD42018086481). A total of 33 trials, involving 2884 patients and 10 treatment arms, were eligible. Huaier significantly increased the treatment response rate (2.48, 1.83-3.35) and survival rate (0.5-year, 1-year and 2-year) and improved immune function without increasing the incidence of adverse effects. Significant efficacy was observed in most subgroups. Network meta-analysis revealed that Huaier was very suitable for combination therapy with TACE and ¹²⁵I particle implantation. Similarly, Huaier also had a good adjuvant therapeutic effect on enhancing platinum (L-OHP and DDP) and adriamycin (ADM). Huaier offers clear advantages for patients with GICs. Moreover, patients should be encouraged to accept Huaier treatment, especially HCC patients undergoing combination therapy with TACE and ¹²⁵I particle implantation.

Production of natural edible melanin by Auricularia auricula and its physicochemical properties

Fermentation conditions of natural edible melanin by Auricularia auricula were optimized to obtain a high melanin yield and physicochemical properties of melanin were firstly investigated. The results indicated that yeast extract, tyrosine and lactose have significant effects on melanin production. Under the proposed optimized conditions, the melanin experimental yield (2.97 g/L) closely matched the value (3.04 g/L) predicted by the second-order model, which provided a statistically prediction of media in submerged fermentation of A. auricula. The yield achieved was 2.14-fold higher compared to the control. It was firstly revealed that tyrosine could stimulate melanin synthesis in A. auricula. The results showed that this melanin had better thermostability and light resistance, and its solubility was relatively high under alkaline conditions. Zn(2+) and Cu(2+) could result in melanin precipitation. The results should be useful for the efficient production of melanin and enable numerous applications in food, cosmetics, pharmacology, medicines and other fields.

Structural Characterization of Melanin Pigments from Commercial Preparations of the Edible Mushroom Auricularia auricula

Many of the most widely consumed edible mushrooms are pigmented, and these have been associated with some beneficial health effects. Nevertheless, the majority of the reported compounds associated with these desirable properties are non-pigmented. We have previously reported that melanin pigment from the edible mushroom Auricularia auricula can protect mice against ionizing radiation, although no physicochemical characterization was reported. Consequently, in this study we have characterized commercial A. auricula mushroom preparations for melanin content and carried out structural characterization of isolated insoluble melanin materials using a panel of sophisticated spectroscopic and physical/imaging techniques. Our results show that approximately 10% of the dry mass of A. auricula is melanin and that the pigment has physicochemical properties consistent with those of eumelanins, including hosting a stable free radical population. Electron microscopy studies show that melanin is associated with the mushroom cell wall in a manner similar to that of melanin from the model fungus C. neoformans. Elemental analysis of melanin indicated C, H, and N ratios consistent with 5,6-dihydroxyindole-2-carboxylic acid/5,6-dihydroxyindole and 1,8-dihydroxynaphthalene eumelanin. Validation of the identity of the isolated product as melanin was achieved by EPR analysis. A. auricula melanin manifested structural differences, relative to the C. neoformans melanin, with regard to the variable proportions of alkyl chains or oxygenated carbons. Given the necessity for new oral and inexpensive radioprotective materials coupled with the commercial availability of A. auricula mushrooms, this product may represent an excellent source of edible melanin.

Impacts of drought stress on soluble carbohydrates and respiratory enzymes in fruit body of Auricularia auricula

In order to study the survival mechanisms to drought stress for fruit body of Auricularia auricula, soluble carbohydrates and respiratory enzymes were investigated. Fruit bodies were exposed to sunlight and were naturally dehydrated. Samples were taken at different levels of water loss (0%, 10%, 30%, 50% and 70%) to measure the content of soluble sugars and polysaccharides. The activities of phosphoglucose isomerase (PGI), combined glucose-6-phosphate dehydrogenase (G-6-PDH) and 6-phosphogluconate dehydrogenase (6-PGDH), and malate dehydrogenase (MDH), were also determined. The results showed that with the increase in water loss, soluble sugars and MDH activity declined, whereas the activities of G-6-PDH and 6-PGDH increased. Soluble polysaccharides content and PGI activity decreased with water loss up to 30% and increased afterwards. These results suggested that the pentose phosphate pathway (PPP), as demonstrated by activities of G-6-PDH and 6-PGDH, could be one of the mechanisms for survival during drought stress in the fruit body of A. auricula. Moreover, soluble polysaccharides may play a part in protecting the fruit body in further drought stress.

Chemical properties of a polysaccharide purified from solid-state fermentation of Auricularia auricular and its biological activity as a hypolipidemic agent

A water-soluble crude polysaccharide was extracted by hot water from Auricularia auricular mycelium grown under solid-state fermentation (SSF). The crude polysaccharide was purified by DEAE Sephadex A-50 and Sephadex G-200 chromatography. Fourier transform infrared spectroscopy and nuclear magnetic resonance ((1) H NMR) spectroscopy were used to investigate the structure of the purified A. auricular polysaccharide (AAP-I) and revealed that it is α-glycosidically linked. After 14 and 28 days of AAP-I orally administered, the AAP-I significantly decreased the levels of total cholesterol, triglyceride, and low-density lipoprotein cholesterol in mice in which hyperlipidemia had been induced by a high fat diet (P < 0.05). The results revealed that AAP-I from SSF of A. auricular mycelium possesses potent hypolipidemic properties. The polysaccharide may be useful as a functional food additive and a hypolipidemic agent.

Hypocholesterolemic effects of Auricularia auricula ethanol extract in ICR mice fed a cholesterol-enriched diet

The cholesterol-lowering properties of Auricularia auricula are commonly attributed to the presence of polysaccharides based on previous research. The present study was designed to investigate the effects of ethanol extract of A. auricula (AAE) on hypercholesterolemia in ICR mice. AAE contained more than 16% (g/g) polyphenolic compounds, excluding other interfering factors such as polysaccharides, water-soluble fibre and protein. Thirty-six mice were randomly assigned to three groups (n = 12). The experimental group was fed cholesterol-enriched diet (CED) with oral administration of AAE (150 mg/kg/d b.w.) for 8-week, normal control group and CED control group received either a regular diet (RD) or CED along with oral administration of equal volume distilled water. Serum lipid profiles and antioxidant status were measured in addition to fecal neutral cholesterol and bile acids. AAE showed a remarkable hypocholesterolemic effect, improving antioxidant status, decreasing the level of total cholesterol and atherosclerosis index, increasing the level of high-density lipoprotein cholesterol and fecal excretion of bile acids. No apparent effects on serum triglycerides, low-density lipoprotein cholesterol, fecal excretion of neutral cholesterol and feeding efficiency were observed among all groups. These results indicated that A. auricula functional components, which prevented hypercholesterolemia contained polyphenolic compounds, in addition to polysaccharides.