User:Csolene/Draft Hericium erinaceus

Hericium erinaceus (also called lion's mane mushroom, monkey head mushroom, bearded tooth mushroom, satyr's beard, bearded hedgehog mushroom, pom pom mushroom, or bearded tooth fungus) is an edible and medicinal mushroom and belongs to the tooth fungus group. Erinaceus literally means “hedgehog” in Latin which is also reflected by the German name “Igel-Stachelbart” and some of its common English names, such as “bearded hedgehog” and “hedgehog mushroom”. Native to North America, Europe and Asia, it can be identified by its long spines, its occurrence on hardwood trees and its tendency to grow as a single clump of dangling spines. The fruit bodies can be harvested and used for culinary or medicinal practices. Hericium erinaceus can be mistaken for other species of Hericium, which are all popular edible fungi that grow across the same range. In the wild, these mushrooms are common during late summer and fall on hardwoods, particularly American beech. Usually H. erinaceus is considered saprophytic as it mostly feeds on dead trees. However, it can also be found on living trees, so it can be considered a weak tree parasite as well. This could indicate an endophytic lifestyle.

Distribution
Hericium species can be found throughout the northern hemisphere. Hericium erinaceus has been used in traditional Chinese medicine for centuries and its production is widespread within Asia, mostly using extensive production practices on wood logs or stumps.

Despite its higher prevalence in Asia, H. erinaceus was first described in North America. Its production there occurs only on a small scale. Most of it is intensive indoor production with only a few small outdoor sites where log cultivation is practiced. Three Hericium species can be found in eastern North America, one being H. erinaceus, the other two H. Americanum and H.coralloides.

Although H. erinaceus is native to Europe, it has been red listed in 13 European countries due to poor germination and establishment. This specific genus fruits between August and December in the United Kingdom, and will continue to produce spores until as late as February in the following year. It is able to withstand cold temperatures and frost conditions.

Strains and yield
In fungi cultivation, fungal strains are analogous to plant varieties in crop breeding. Fungal strains comprise clonal descendants of a single isolation from one fungal colony in a pure culture. Hericium spp. grow in the wild in North America, Europe and Asia and, although there is considerable scientific research about them, they are not commonly industrially produced. Accordingly, there are few commercially available strains in the USA or Europe and little or no breeding for higher yield or other favorable traits has occurred.

A study conducted at Cornell (college of agriculture and life sciences) has shown no statistical significance in yield difference between different strains of H. erinaceus. The same study showed that yield varied significantly depending on the number of years after inoculation, with peak production during the third and fourth years. Peak production levels were similar to the commercial yield of forest cultivated shiitake mushrooms, one of the only economically viable mushrooms that can be produced in the forest. Production trials in Egypt report yields of H.erinaceus averaging at 165g per 1kg medium.

Product use
Hericium erinaceus produces edible fruiting bodies that have both culinary and traditional medicinal uses. The mycelium is also used medicinally.

Culinary uses
Hericium erinaceus is popular with chefs in gourmet cooking, however the mushroom is largely unknown and the demand for it is small despite increasing consumer interest. Alongside shiitake (Lentinus edodes) and oyster (Pleurotus ostreatus) mushrooms, H. erinaceus can be classified as a specialty mushroom and culinarily utilized in a similar fashion as these other, more prevalent edible mushrooms, e.g. by pan-frying in butter. Its flavor is said to be comparable to that of lobster. The production of specialty mushrooms in the USA increased by about 23% between 2010 and 2018 from 16.4 to 20.1 million lbs (7.4 to 9.1 million kg). This increasing consumer interest in specialty mushrooms has encouraged the improvement of shiitake strains.

Medicinal uses
Hericium erinaceus has been used in traditional Chinese medicine to treat gastritis for over a millennium. It is also employed to reduce inflammation and boost the immune system whereby it is often administered as tablets of dried and powdered fruiting bodies. It can also be purchased as H. erinaceus extract. This is produced by first cooking pulverized, dried fruiting bodies in water and/or alcohol to break down fungal cell walls and release both water soluble and insoluble compounds from within the cells. The liquid is then removed, leaving behind a powder that can be purchased and consumed in loose form or in capsules.

In an experiment in which compounds from a H. erinaceus culture broth were extracted and given to mice, the compounds appeared to have antitumor effects. The test group of mice showed to have an increased amount of T cells and macrophages than the control group, indicating an immuno-enhancing effect of these compounds. Another study indicated that the consumption of H. erinaceus extract could induce apoptosis of human monocytic leukemia cells.

Research suggests that certain compounds in H. erinaceus stimulate the biosynthesis of nerve growth factor (see Chemistry) which could have preventative and therapeutic effects on degenerative neuronal disorders, including Alzheimer’s disease. Furthermore, research suggests the intake of H. erinaceus could potentially reduce depression and anxiety.

Nutritive value
The nutritive value of H. erinaceus fruiting bodies is relatively high, containing 57% carbohydrates, 3.52% fats, 7.81% fiber, 22.3% protein and 9.35% ash of dry matter. Depending on the study, the number of amino acids detected in the fruiting bodies has varied between 14 and 19,. Potassium and phosphorus occur in large concentrations of 254 and 109 mg/100 g dry matter, respectively.

Chemistry
There are bioactive, medicinally interesting compounds in both the fruiting body and the mycelium of H. erinaceus. The fungus contains a number of polysaccharides, such as β-glucan, heteroglucans, and heteroxylans, as well as several cyathane derivative diterpenoids known as hericenones and erinacines. Hericenones and erinacines have shown to have positive effects on the biosynthesis of nerve growth factor (see Medicinal uses). Different analyzes of the aroma compounds in lion’s mane fruiting bodies have determined different dominant compounds, including 1-octen-3-ol, 2-methyl-3-furanthiol, 2-ethylpyrazine and 2,6-diethylpyrazine.

Morphology
The fruitbodies of H. erinaceus are large, irregular bulbous tubercules. They are 5-40 cm in diameter and are dominated by crowded, hanging, spore-producing spines, which are 1-4 cm long. Fruitbodies and spines colour is white to cream, but can turn yellowisch brown when they get older.

The hyphal system is monomitic, amyloid, and comprises thin to thick-walled hyphae that are about 3 – 15 um wide. The hyphae also contain clamped septa and gloeoplerous elements (filled with oily, resinuous substances), which can come into the hymenium as gloeocystidia.

The basidia are 25-40 um long and 5-7 um wide, contain four spores each and possess a basal clamp. The white amyloid basidiospores measure around 5-7 um in length and 4-5 um in width. The spore shape is described as subglobose to short ellipsoid and the spore surface is smooth to finely roughened.

Development
The fruitbodies of H. erinaceus are mainly produced annually from August to November in Europe. It was observed that H. erinaceus could fruit intermittently for 20 years on the same dead tree. It is hypothesized that H. erinaceus can survive for 40 years. The mating system of H. erinaceus species found in the USA was shown to be bifactorially heterothallic.

The monokaryotic mycelium growth of H.erinaceus is slower than dikaryotic growth and only about a low percentage of monokaryotic cultures yield fruitbodies. Monokaryotic fruitbodies are also smaller than dikaryotic fruitbodies. The monokaryotic mycelium was found to produce fusoid to subglobose chlamydospores of 6-8 x 8-10 um size. These spores can stay viable more than 7 years and be stored under anaerobic conditions. Chlamydospore germination requires 30 to 52 hours, with a germination success rate of 32 to 54%.

Spore production is highest at midday, relative to temperature increase and relative humidity decrease. Daily trends towards lower relative humidity can favor sporulation, however levels of relative humidity that are too low do not favor high total spore production.

Disease
Brennandania lambi (Acari: Pygmephoroidea) is a mite pest of fungi culture in China. This mite can develop and reproduce on the mycelium of H. erinaceus. Farm hygiene and heating treatments are the most important pest management strategies that should be done to counter this acari.

Biocontrol agent
The use of H.erinaceus to control tomato diseases has been studied. Fungus extract inhibited the mycelial growth of tomato pathogenic fungi, including Phytophthora capsici, and the growth of the bacteria Ralstonia solanacearum.

Competition with other fungi
Hericium species are good competitors against other wood colonisers. They show the ability to maintain their place on dead wood, also when confronted with secondary colonizers like Trametes versicolor and Stereum hirsutum. Hericium erinaceus has shown to be slightly more competitive than other fungi tooth species including Creolophus cirrhatus and Hericium coralloides.

Substrate requirements
As a saprophyte that occurs on dead wood, H. erinaceus requires an adequate substrate. This substrate has to provide suitable carbon and nitrogen sources, a certain pH value and ideal carbon/nitrogen ratio.

Many different substrates have been successfully utilized for this mushroom cultivation. Depending on the type of cultivation, the substrate can be either solid (artificial log) or liquid (submerged culture and deep submerged culture). The solid substrate is most commonly a mixture of sawdust and different complements. The sawdust is made up of hardwood or conifer. It can be enriched with wheat bran, wheat straw, soybean meal, corn meal, rice bran and rice straw. For example, H. erinaceus strains grow on beech sawdust substrate enriched with wheat bran (20%), rye grain (25%), soybean meal (7%), rape meal (10%) or meat-osseous flour (6%). An example of a liquid substrate composition can be: glucose for the carbon source, soybean powder, corn powder, and wheat bran powder as a complex nitrogen source.

The pH values most suitable for the favorable growth of H. erinaceus were observed in the range of 5.0 - 9.0 and the best was pH 6.0.

Climate requirements
H. erinaceus requires a humid environment for its growth: 85 to 90% of relative humidity in the air and daily water spraying when grown indoors.

The incubation temperature most suitable for the mycelial growth of H. erinaceus was found to be 25°C and the optimum temperature for vegetative growth was observed to be 26°C.

H. erinaceus is unable to grow with a water potential lower than -5 Mpa.

Cultivation techniques
The artificial cultivation of H. erinaceus was first reported in China in 1988. It is cultivated using artificial logs, bottles and polypropylene bags. However, this type of artificial cultivation is not suitable for industrialized production due to its low yield and long the cultivation cycle takes.

Submerged culture is another type of artificial cultivation of H. erinaceus whereby the fungus is grown in a liquid medium. Using this method, a large number of mycelia can be obtained in a short period of time. Bioactive compounds can be sourced from the fruiting bodies, submerged-cultivated mycelial biomass or liquid-cultivated broth. Growers optimize the culture medium composition, so as to obtain simultaneously high yields of H. erinaceus mycelial biomass, exopolysaccharides, and intracellular polysaccharides.

For the production of mushroom fruiting bodies, various forms of solid substrate are employed. On the other hand, submerged fermentation is preferable for the production of mycelial biomass and biologically active metabolites in order to produce a more uniform biomass and pharmaceutical products.

Growth regulators, e.g., 2,4-Dichlorophenoxyacetic acid and gibberellin, were observed to have an advantageous impact on spore germination. Other technologies, like red and green laser light of low intensity, stimulated spore germination as well as the vegetative growth of mycelium. Argon and helium lasers also contributed to the acceleration of fructification so that the weight of a single fruitbody was increased and the yield of the fruitbodies were increased by 36–51%.

Isolation of wild strains for cultivation
Wild strains of Hericium spp. can be isolated and cultivated by first gathering fruiting bodies from fallen trees in the mushroom’s natural habitat. The fruiting bodies can then be opened to attain pieces of their inner spore-producing tissue. This tissue is then placed onto petri dishes with agar to cultivate fungal colonies at 25 °C. After several transfers to new petri dishes to verify the purity of the strain, it can be kept at -80 °C for long-term storage.

Genetic & breeding
A lack of genetic and molecular knowldege prevent the development of elite cultivars of H. erinaceus. Breeding targets in mushrooms are quantitaty of bioactive compounds, higher yields, better quality and higher pest and disease resistance. It was shown that a lot of traits of interest might by governed by QTLs (quantitative traits loci).