Increasing the production of the bioactive compounds in medicinal mushrooms: an omics perspective

Macroscopic fungi, mainly higher basidiomycetes and some ascomycetes, are considered medicinal mushrooms and have long been used in different areas due to their pharmaceutically/nutritionally valuable bioactive compounds. However, the low production of these bioactive metabolites considerably limits the utilization of medicinal mushrooms both in commerce and clinical trials. As a result, many attempts, ranging from conventional methods to novel approaches, have been made to improve their production. The novel strategies include conducting omics investigations, constructing genome-scale metabolic models, and metabolic engineering. So far, genomics and the combined use of different omics studies are the most utilized omics analyses in medicinal mushroom research (both with 31% contribution), while metabolomics (with 4% contribution) is the least. This article is the first attempt for reviewing omics investigations in medicinal mushrooms with the ultimate aim of bioactive compound overproduction. In this regard, the role of these studies and systems biology in elucidating biosynthetic pathways of bioactive compounds and their contribution to metabolic engineering will be highlighted. Also, limitations of omics investigations and strategies for overcoming them will be provided in order to facilitate the overproduction of valuable bioactive metabolites in these valuable organisms.

A RESEARCH ON QUALITY EVALUATION OF EIGHT WILD EDIBLE MACROFUNGI COLLECTED FROM EAST MEDITERRANEAN REGION OF TURKEY

Eight edible macrofungal species ( Suillus collinitus, Rhizopogon roseolus, Lactarius sanguifluus, Lycoperdon molle, Ganoderma adspersum, Pleurotus cornucopiae, Lycoperdon perlatum, Macrolepiota procera ) grown in Osmaniye were studied. Besides the evaluation of fresh forms, the mushrooms were dried at 40˚C, and the color, texture, protein and mineral contents, and bioactivities (total phenolic content, (TPC) and antioxidant activities by DPPH, FRAP and ABTS techniques) were determined. The protein, macro and micro mineral contents of dried samples were in range of 11.31-55.31%, 132.75-50844.80 and 0.30-812.05 mg/kg, respectively. TPC of fresh samples were 10227.13-42216.89 mg gallic acid equivalent (GAE)/kg dry matter (DM) in methanolic solution, 3625.31-28809.99 mg GAE/kg DM in ethanolic solution, and decreased by drying process. ABTS method yielded higher results in fresh specimens, however DPPH method in ethanol and FRAP method in methanol were the superior in dried forms.

Ergothioneine: a potential antioxidative and anti-melanosis agent for food quality preservation

The global population increase has increased the demand for food products. However, post-harvest deterioration due to oxidation and discoloration results in a drastic loss of food quality and supply. Thus, research has focused on developing strategies to minimize such losses. One of those strategies includes the application of ergothioneine (ET), a potent hydrophilic antioxidant, to several food products so as to overcome their short shelf-life. ET can be synthetic or derived from several species of edible mushrooms and their extracts, which are known sources of natural ET. Given the reported potential of ET in food quality preservation, this review compiles the recent applications of ET as a preservative for maintaining the quality of food commodities.

Edible Mushrooms as a Natural Source of Food Ingredient/Additive Replacer

Although mushrooms have been exploited since ancient times because of their particular taste and therapeutic properties, the interest in edible species as a source of ingredients and bioactive compounds is recent. Their valuable nutritional contents in protein, dietary fiber and bioactive compounds make them ideal candidates for use in foods in efforts to improve their nutritional profiles. This trend is in line with the consumer's growing demand for more plant-based foods. The present review paper explores different studies focused on the use of common edible mushrooms as an ingredient and additive replacer by using them in fresh, dried, or even extract forms, as meat, fat, flour, salt, phosphates, and antioxidant replacers. The replacement of meat, fat, flour, and salt by mushrooms from commercial species has been successful despite sensorial and textural parameters can be affected. Moderate concentrations of mushrooms, especially in powder form, should be considered, particularly in non-familiarized consumers. In the case of antioxidant and antimicrobial properties, results are variable, and more studies are necessary to determine the chemical aspects involved.

Effects of ergothioneine-enriched mushroom extract on oxidative stability, volatile compounds and sensory quality of emulsified sausage

OBJECTIVE

The aim of this work was to assess the effect of ergothioneine (ESH)-enriched mushroom extract on oxidative stability, volatile compounds, and sensory quality of emulsified sausage.

METHODS

The ESH content was determined by high performance liquid chromatography. The antioxidant activity of Flammulina velutipes (F. velutipes) extract was determined through radical-scavenging activity of 1,1 diphenyl-2-picryl-hydrazyl, 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl radicals. Four different groups of emulsified sausage were manufactured: control, no antioxidants; BHA, 0.01% butylated hydroxyanisole; EEME, 0.8% ESH-enriched mushroom (F. velutipes) extract; AE, 0.012% authentic ESH, after storage for 14 days (at 4°C), the quality of sausage including oxidative stability (2-thiobarbituric acid reactive substances and protein carbonyls content), volatile compounds and sensory quality were studied.

RESULTS

It was demonstrated that adding ESH-enriched F. velutipes extract to sausage could effectively prevent lipid and protein oxidation, and its efficacy was equivalent with 0.01% BHA. During meat processing, the ESH mainly contributed to the antioxidative activity of F. velutipes extract. The flavor and sensory attributes of emulsified sausage were improved through adding ESH-enriched F. velutipes extract.

CONCLUSION

Accordingly, the extract of F. velutipes contained high-level of ESH and could be a good antioxidant candidate for processed meat production.

Functional identification of ergothioneine transporter in rainbow trout (Oncorhynchus mykiss)

(2S)-3-(2-sulfanylidene-1,3-dihydroimidazol-4-yl)-2-(trimethylazaniumyl)propanoate (ergothioneine, ET) is hydrophilic antioxidant produced only by certain low-level organisms, but has been reported in the organs of some animals upon dietary intake, facilitated by the ergothioneine transporter (ETT). In this study, it was hypothesised that ETT is involved in the uptake of ET from diet in salmonids. The mechanism of ET uptake was evaluated through knockdown of candidate gene encoding ETT in a cell line (RTG-2) from rainbow trout (Oncorhynchus mykiss). ETT gene expression in blood cells and certain tissues from rainbow trout was also investigated as ET from the diet is expected to be carried over to the muscle. Knockdown of an ETT candidate (E1) in RTG-2 cells resulted in a remarkable decrease in E1 mRNA expression; uptake of ET was lower in the knocked group than in the control group suggesting that E1 functions as an ETT for rainbow trout. Furthermore, the expression of ETT gene in different tissues including the muscle points to ET uptake from the diet to the muscle of salmonids. In conclusion, this study partly reveals the possible pathway underlying ET uptake from the diet and its deposition in the muscle of edible fish species.

Edible Mushrooms as Functional Ingredients for Development of Healthier and More Sustainable Muscle Foods: A Flexitarian Approach

Consumers are increasingly interested in nutritious, safe and healthy muscle food products with reduced salt and fat that benefit their well-being. Hence, food processors are constantly in search of natural bioactive ingredients that offer health benefits beyond their nutritive values without affecting the quality of the products. Mushrooms are considered as next-generation healthy food components. Owing to their low content of fat, high-quality proteins, dietary fibre and the presence of nutraceuticals, they are ideally preferred in formulation of low-caloric functional foods. There is a growing trend to fortify muscle food with edible mushrooms to harness their goodness in terms of nutritive, bioactive and therapeutic values. The incorporation of mushrooms in muscle foods assumes significance, as it is favourably accepted by consumers because of its fibrous structure that mimics the texture with meat analogues offering unique taste and umami flavour. This review outlines the current knowledge in the literature about the nutritional richness, functional bioactive compounds and medicinal values of mushrooms offering various health benefits. Furthermore, the effects of functional ingredients of mushrooms in improving the quality and sensory attributes of nutritionally superior and next-generation healthier muscle food products are also highlighted in this paper.

Effect of squid pen chitooligosaccharide and epigallocatechin gallate on discoloration and shelf-life of yellowfin tuna slices during refrigerated storage

This study evaluated the effects of treatments of squid pen chitooligosaccharide (COS) or epigallocatechin gallate (EGCG) or COS/EGCG mixture (1:1, w/w) at different concentrations (0, 200, and 400 mg/kg) on the discoloration and quality changes in yellowfin tuna slices stored at 4 °C for 12 days. Tuna slices added with 200 and 400 mg/kg of COS (C2 and C4, respectively) showed the lowest reduction in oxymyoglobin and a* value (redness) ascertained by the lower metmyoglobin formation than other samples. Additionally, C2 and C4 samples showed a lower total viable count and TBARS value than the remaining samples. EGCG alone and its mixture with COS exhibited lower efficacy in retaining the quality loss than COS alone. COS at both levels effectively reduced the metMb formation. It maintained the redness with sensory acceptability of slices up to 9 days, and C4 sample prolonged shelf-life for 12 days based on the microbiological limit.

The biology of ergothioneine, an antioxidant nutraceutical

Ergothioneine (ERG) is an unusual thio-histidine betaine amino acid that has potent antioxidant activities. It is synthesised by a variety of microbes, especially fungi (including in mushroom fruiting bodies) and actinobacteria, but is not synthesised by plants and animals who acquire it via the soil and their diet, respectively. Animals have evolved a highly selective transporter for it, known as solute carrier family 22, member 4 (SLC22A4) in humans, signifying its importance, and ERG may even have the status of a vitamin. ERG accumulates differentially in various tissues, according to their expression of SLC22A4, favouring those such as erythrocytes that may be subject to oxidative stress. Mushroom or ERG consumption seems to provide significant prevention against oxidative stress in a large variety of systems. ERG seems to have strong cytoprotective status, and its concentration is lowered in a number of chronic inflammatory diseases. It has been passed as safe by regulatory agencies, and may have value as a nutraceutical and antioxidant more generally.

Impact of mushroom (Pleurotus eryngii) flour upon quality attributes of wheat dough and functional cookies-baked products

The objective of this study was to create a healthier version of a commonly consumed baked food (cookies) by replacing some of the wheat flour with a nutraceutical-rich mushroom flour. The impact of incorporating different levels of powdered mushroom (Pleurotus eryngii) flour on the rheological properties of the cookie dough and the final cookies was therefore determined. The rheological properties of wheat dough supplemented with 0%-25% (w/w) of mushroom flour were analyzed using a Mixolab instrument and a shear rheometer. Increasing the ratio of mushroom-to-wheat flour in the doughs increased the peak and final viscosities, but decreased dough stability and elastic modulus. Sensory evaluation using an orthogonal test showed that 15% mushroom flour, 10% maltodextrin, and 1.5% sodium bicarbonate were the optimal composition for producing cookies with the best sensory score. In conclusion, our results showed that cookies with acceptable textures and appearances could be produced by replacing up to 15% of wheat flour with mushroom flour.

Effects of Rosemary Oil (Rosmarinus officinalis) on the Shelf-Life of Minced Rainbow Trout (Oncorhynchus mykiss) during Refrigerated Storage

The effects of three concentrations (0.2%, 1% and 3%) of rosemary oil (RO) on the freshness indicators, oxidative stability, fatty acid and biogenic amine (BA) contents of minced rainbow trout muscle (MTM) were investigated after different periods of storage (three and nine days) at 4 ± 1 °C. Moreover, the terpene and sesquiterpene contents in the treated MTM were also measured. RO treatment improves the pH, oxidative stability of the lipids and the FA profile, which resulted in a significant extension of MTM shelf-life. Storage time influenced all freshness indicators, with the exception of yellowness and chroma. Treatment with RO had a positive effect, leading to low BA content, especially putrescine, cadaverine, tyramine and histamine. Differences in BA were also found to be due to storage time, with the exception of spermidine, which was not influenced by time. Moreover, the presence of the terpenoid fraction of RO in MTM improved the quality of this ready-to-cook fish food.

Baking reduces prostaglandin, resolvin, and hydroxy-fatty acid content of farm-raised Atlantic salmon (Salmo salar)

The consumption of seafood enriched in n-3 polyunsaturated fatty acids (PUFA) is associated with a decreased risk of cardiovascular disease. Several n-3 oxidation products from eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (22:6n-3) have known protective effects in the vasculature. It is not known whether the consumption of cooked seafood enriched in n-3 PUFA causes appreciable consumption of lipid oxidation products. We tested the hypothesis that baking Atlantic salmon (Salmo salar) increases the level of n-3 and n-6 PUFA oxidation products over raw salmon. We measured the contents of several monohydroxy-fatty acids (MHFA), prostanoids, and resolvins. Our data demonstrate that baking did not change the overall total levels of MHFA. However, baking resulted in selective regioisomeric loss of hydroxy fatty acids from arachidonic acid (20:4n-6) and EPA, while significantly increasing hydroxyl-linoleic acid levels. The contents of prostanoids and resolvins were reduced several-fold with baking. The inclusion of a coating on the salmon prior to baking reduced the loss of some MHFA but had no effect on prostanoid losses incurred by baking. Baking did not decrease n-3 PUFA contents, indicating that baking of salmon is an acceptable means of preparation that does not alter the potential health benefits of high n-3 seafood consumption. The extent to which the levels of MHFA, prostanoids, and resolvins in the raw or baked fish have physiologic consequence for humans needs to be determined.

Edible mushroom (Flammulina velutipes) extract inhibits melanosis in Kuruma shrimp (Marsupenaeus japonicus)

This study compared the potential of an aqueous extract of an edible mushroom (Flammulina velutipes) to prevent melanosis in cultured Kuruma shrimp (Marsupenaeus japonicus) with other antimelanosic compounds in vivo. The mushroom extract contained 9.1 mg/mL ergothioneine (ESH). Immersion of live full-grown shrimp in a 0.5% w/v solution of mushroom extract significantly reduced PPO activity in shrimp hemolymph. In addition, expression of the prophenoloxidase (proPO) gene decreased in hemocytes, suggesting that the extract blocked the activation of the proPO cascade. Consequently, the development of melanosis in the treated shrimp was significantly suppressed during ice storage. Treatment with a 0.05% w/v solution of sodium ascorbate and 4-hexyl-1,3-benzenediol had the same effect. In vitro experiments showed that ESH effectively inhibited PPO activity and activation of the proPO cascade in hemocyte lysate supernatant. This study suggests that in vivo application of F. velutipes mushroom extract is an effective natural alternative to synthetic antimelanosic agents to inhibit postmortem melanosis in shrimp. Practical Application: The extract of an edible mushroom (F. velutipes) containing ergothioneine can be a promising natural alternative to synthetic antimelanosic agents used to prevent postharvest melanosis in shrimp and other crustaceans. Furthermore, utilization of the mushroom trimmings could also help address the growing concerns on the disposal of such agricultural wastes and instead use it into a novel purpose as a source of antimelanosic and antioxidants for food and industrial application.

Value-added use of mushroom ergothioneine as a colour stabilizer in processed fish meats

BACKGROUND

Ergothioneine (ESH), a potent antioxidant, has been found in certain edible mushrooms. Our previous research showed that ESH extracted from the edible mushroom Flammulina velutipes has a positive effect on the colour stability of beef and tuna meat. The purpose of the present study was to compare the efficacy and applicability of ESH extracts prepared from different mushroom species as a colour stabilizer in fish meats.

RESULTS

Levels of ESH higher than 2.8 mg mL(-1) were found in extracts prepared from the fruiting bodies of F. velutipes, Lentinula edodes, Pleurotus cornucopiae and Pleurotus eryngii and the processing waste of F. velutipes. When 1 mL of each of the extracts was added to 100 g of minced bigeye tuna and yellowtail meats, the bright-red colour remained after 5 and 2 days, respectively, of ice storage. The anti-discoloration efficacy of 1 mL of the extracts prepared from 10 g of the fresh waste portion of F. velutipes was similar to that of its fruiting body or 0.5 g kg(-1) of sodium ascorbate when added to 100 g of minced bigeye tuna meat under ice storage.

CONCLUSION

The results of this study clearly showed that ESH prepared from different mushroom species stabilized the colour of fish meats, and the extract from the F. velutipes was the most effective.

Antioxidative activities of hydrophilic extracts prepared from the fruiting body and spent culture medium of Flammulina velutipes

Antioxidative properties of hydrophilic extracts prepared from the fruiting body and spent culture medium of Flammulina velutipes were evaluated by monitoring the total reducing power ability (RPA) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity (RSA), together with antioxidative activities against lipid oxidation in homogenates of yellowtail dark muscle and autoxidation of oxymyoglobin (oxyMb) purified from yellowtail dark muscle. Generally, all of the extracts had RPA, RSA and antioxidative activities against lipid oxidation and oxyMb autoxidation. Extracts prepared from the fruiting body of F. velutipes with a higher ergothioneine (ESH) content exhibited a stronger delay of the autoxidation activity of oxyMb, whereas extracts prepared from the spent culture medium of F. velutipes with higher phenolics content showed more efficient antioxidant capacity against lipid oxidation. On the other hand, the amount of ESH was distributed highest in the inedible (base and mycelium) parts of the mushroom. These results suggest that the inedible parts and spent culture medium of F. velutipes could potentially be considered as a potent and readily available source of natural antioxidants.

Effects of ergothioneine from mushrooms (Flammulina velutipes) on melanosis and lipid oxidation of kuruma shrimp (Marsupenaeus japonicus)

The antimelanosic and antioxidative properties of a hot water extract prepared from the fruiting body of the edible mushroom (Flammulina velutipes) were evaluated by dietary supplementation in Kuruma shrimp (Marsupenaeus japonicus) for possible aquaculture application. The extract contained ergothioneine (ERT) at a level of 2.05 mg/mL. A commercial standard of l-ergothioneine (l-ERT) and the mushroom extract showed inhibitory activity against mushroom polyphenoloxidase (PPO). Feeding of the extract had no adverse effects on the immune systems of the shrimp under the present experimental conditions. Supplementation of the extract in the diet significantly suppressed PPO activities in the hemolymphs of the shrimp. Expression of the prophenoloxidase (proPO) gene decreased in the hemocyte of the Kuruma shrimp fed with the mushroom extract. Consequently, development of melanosis was significantly suppressed in the supplement fed shrimp during ice storage. Lipid oxidation was also effectively controlled in the supplement fed group throughout the storage period. In vitro experiments showed that l-ERT effectively inhibited the activation of proPO in the hemocyte lysate supernatant (HLS). The transcript of the proPO gene in the hemocyte showed lower expression in the l-ERT-treated HLS. It was concluded that dietary supplementation of the mushroom extract in shrimp could be a promising approach to control post mortem development of melanosis and lipid oxidation in shrimp muscles.