Quantification of the bioactive compound eritadenine in selected strains of shiitake mushroom (Lentinus edodes)

Enhancing Eritadenine Production in Submerged Cultures of Shiitake (Lentinula edodes Berk. Pegler) Using Blue LED Light and Activated Charcoal. Revealing Eritadenine's Novel In Vitro Bioherbicidal Activity Against Chrysanthemum morifolium

Eritadenine from shiitake mushroom is a secondary metabolite with hypocholesterolemic, hypotensive and antiparasitic properties, thus promising for pharmaceutical and agricultural applications. Eritadenine is obtained from submerged mycelial cultures of shiitake, but the actual yields remain unsatisfactory to explore potential applications or industrial-scale production. In this study, green and blue LED lights were tested to increase yields of eritadenine in submerged cultures of shiitake. Notably, blue LEDs increased yields by 13-14 times, reaching 165.7 mg/L, compared to darkness (11.2 mg/L) and green light (12.1 mg/L) (p < 0.05, Tukey test). Nitrogen sources yeast extract (YE) and peptone (at 2 g/L) increased eritadenine production. YE promoted 22.6 mg/L, while peptone 18.3 mg/L. The recovery of eritadenine was evaluated using amberlite and activated charcoal (AC) adsorption isotherms. AC demonstrated the highest adsorption rate, with 75 mg of eritadenine per gram of AC, according to the Freundlich isotherm. The desorption rate reached 93.95% at pH 10. The extract obtained from submerged cultures had eritadenine content of 63.31%, corresponding to 87.86% of recovery, according to HPLC analysis. Furthermore, the novel bioherbicidal potential of eritadenine was tested on in vitro Chrysanthemum morifolium plants. The cultures extract containing eritadenine had a detrimental impact on plant development, generating mortality of 100% at 3%, 0.5%, and 0.25%. Moreover, pure eritadenine exhibited a phytotoxic effect similar than glyphosate on leaves, stems and roots. These findings highlight the significant bioherbicidal properties of eritadenine. Further studies are needed to understand the biosynthetic pathway of eritadenine and its bioherbicidal properties on weeds and illicit crops.

Emerging technologies for the extraction of bioactives from mushroom waste

Extraction of bioactive compounds for application in nutraceuticals is gaining popularity. For this, there is a search for low-cost substrates that would make the end product and the process more economical. Mushroom waste (stalk, cap, stem etc.) is one such high valued substrate that has received much attention recently due to its rich reserves of terpenoids, polyphenols, sesquiterpenes, alkaloids, lactones, sterols, antioxidative vitamins, anthocyanidins, glycoproteins and polysaccharides, among others. However, there is a need to identify green and hybrid technologies that could make the bioactive extraction process from these substrates safe, efficient and sustainable. To this effect, many emerging technologies (supercritical fluid, ultrasound-, enzyme- and microwave-assisted extraction) have been explored in the last decade which have shown potential for scale-up with high productivity. This review systematically discusses such technologies highlighting the current challenges faced during waste processing and the research directives needed for further advancements in the field.

Medicinal Mushrooms as Multicomponent Mixtures-Demonstrated with the Example of Lentinula edodes

Medicinal mushrooms are multicomponent mixtures (MOCSs). They consist of a large number of individual compounds, each with different chemical structures, functions, and possible pharmacological activities. In contrast to the activity of an isolated pure substance, the effects of the individual substances in a mushroom or its extracts can influence each other; they can strengthen, weaken, or complement each other. This results in both advantages and disadvantages for the use of either a pure substance or a multicomponent mixture. The review describes the differences and challenges in the preparation, characterization, and application of complex mixtures compared to pure substances, both obtained from the same species. As an example, we use the medicinal and culinary mushroom Lentinula edodes, shiitake, and some of its isolated compounds, mainly lentinan and eritadenine.

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.

Antibacterial activity and antibacterial mechanism of ethanol extracts of Lentinula edodes (Shiitake) and Agaricus bisporus (button mushroom)

The aim of the present work was the comparison of antimicrobial activity, mechanism and components of the ethanol extract (EE) from Lentinula edodes Berk (Pegler) and Agaricus bisporus Sing (Lange). The main component of EE of A. bisporus was dianhydromannitol (20.1%), while isosorbide/dianhydromannitol (21.8%) was detected at a high rate in L. edodes ethanol extract by GC-MS . The common phenolic acids were determined as chlorogenic acid, syringic acid, rutin, p-coumaric acid, ferulic acid, 2-hydroxy cinnamic acid, protocatechuic acid, abscisic acid, and trans-cinnamic acid in both mushroom extract by HPLC-MWD . The MICs (minimum inhibitory concentration) of L. edodes EE on Klebsiella pneumoniae, Staphylococcus aureus, Enterococcus faecalis and Acinetobacter baumannii were between 5.1 mg ml^-1 and 6.01 mg ml^-1, while MICs of A. bisporus EE on the pathogens were between 5.8 mg ml^-1 and 9.54 mg ml^-1. The highest DRA decrease was in E. faecalis (69.1%) for L. edodes and S. aureus (71.0%) for A. bisporus in the 20th minute. As a result, L. edodes and A. bisporus have a similar antibacterial effect on the pathogens, and this inhibition effect caused DNA, protein leakage and destruction of permeability of bacterial cell membrane by bioactive molecules in mushroom extract.

Edible Mushrooms: A Comprehensive Review on Bioactive Compounds with Health Benefits and Processing Aspects

Mushrooms are well-known functional foods due to the presence of a huge quantity of nutraceutical components. These are well recognized for their nutritional importance such as high protein, low fat, and low energy contents. These are rich in minerals such as iron, phosphorus, as well as in vitamins like riboflavin, thiamine, ergosterol, niacin, and ascorbic acid. They also contain bioactive constituents like secondary metabolites (terpenoids, acids, alkaloids, sesquiterpenes, polyphenolic compounds, lactones, sterols, nucleotide analogues, vitamins, and metal chelating agents) and polysaccharides chiefly β-glucans and glycoproteins. Due to the occurrence of biologically active substances, mushrooms can serve as hepatoprotective, immune-potentiating, anti-cancer, anti-viral, and hypocholesterolemic agents. They have great potential to prevent cardiovascular diseases due to their low fat and high fiber contents, as well as being foremost sources of natural antioxidants useful in reducing oxidative damages. However, mushrooms remained underutilized, despite their wide nutritional and bioactive potential. Novel green techniques are being explored for the extraction of bioactive components from edible mushrooms. The current review is intended to deliberate the nutraceutical potential of mushrooms, therapeutic properties, bioactive compounds, health benefits, and processing aspects of edible mushrooms for maintenance, and promotion of a healthy lifestyle.

Molecular identification of Shiitake [Lentinula edodes Berk (Pegler)] and production of secondary metabolites with biotechnological potential

The Shitake mushroom (Lentinula edodes) is the second most-consumed mushroom in the world; in Colombia, it is cultivated and commercialized on a small scale in some supermarkets. Little is known about the precedence, nutritional and medicinal properties of Shiitake produced in Colombia. In this study, four shiitake isolates were grown in Colombia (LEUCO1, LEUCO2, LEUCO3, and LEUCO4) were sequenced in their ITS genes and evaluated for the production of three medicinal metabolites, eritadenine, ergotioneine and β-glucans (1,3-1, 6), using submerged culture. Genetic analysis revealed that all the isolates were close and related to the Japanese strain Cr62. LEUCO1 and LEUCO2 showed a distance of 0.000, as well as LEUCO3 and LEUCO4. All four isolates produced erythadenin in a range of 26.3-8.6 mg / L, with the best performance of LEUCO1 at 26.3 mg / L (p <0.05). Ergotioneine was produced with similar statistical yields in all the isolates with an average of 0.7 mg / g of dry weight biomass (DW). Β-glucans (1.3-1.6) were produced with yields of 5.6 - 3.8% of DW biomass, with the best values ​​for LEUCO2 and the lowest for LEUCO4 (p <0.05). In conclusion, we identified low genetic diversity in the four isolates, corresponding to two haplotypes with minimal genetic difference between them, related to the Japanese strain Cr62, indicating that Colombian farmers cultivate almost the same strains of shitake. Secondary metabolites, eritadenine, β-glucans and ergotioneine were found in promising yields useful for the pharmaceutical and food industries. More studies should be conducted to improve the yield of shitake metabolites through new growing conditions for industrial production and to find metabolic pathways and related genes.

Effect of traditional and modern culinary processing, bioaccessibility, biosafety and bioavailability of eritadenine, a hypocholesterolemic compound from edible mushrooms

Eritadenine is a hypocholesterolemic compound that is found in several mushroom species such as Lentinula edodes, Marasmius oreades, and Amanita caesarea (1.4, 0.7 and 0.6 mg per g dry weight, respectively). It was synthesized during all developmental stages, being present in higher concentrations in the skin of shiitake fruiting bodies. When subjected to traditional cooking, grilling followed by frying were more adequate methodologies than boiling or microwaving to maintain its levels. Modern culinary processes such as texturization (with agar-agar) and spherification (with alginate) also interfered with its release. Grilling and gelling using gelatin enhanced eritadenine's bioaccessibility in an in vitro digestion model. An animal model (where male and female rats were administered 21 and 10 mg per kg animal per day of eritadenine) indicated that intake of the compound was safe under these concentrations; it reached the liver and reduced the atherogenic index (TC/HDL) in rat sera. Thus, it might be used to design a functional food.

Extraction of bioactive compounds against cardiovascular diseases from Lentinula edodes using a sequential extraction method

Three extraction methods were sequentially combined to obtain fractions from Lentinula edodes (shiitake mushrooms) containing bioactive compounds against cardiovascular diseases (CVDs). Fruiting bodies were first extracted with plain water, obtained residue was then submitted to supercritical fluid extraction (SFE) and remaining residue submitted to hot water extraction. Sequential design allowed reutilization of the nonextracted material as raw material for the successive extractions increasing extraction yields and separating interesting compounds. Obtained fractions contained different amounts of ß-glucans, chitins, eritadenine, lenthionine, ergosterol, proteins/peptides and phenolic compounds conferring them different bioactivities. Water soluble fractions showed high antioxidant activities (ABTS^+• and DPPH^• scavenging capacity and reducing power), they were also able to inhibit one of the main enzymes involved in hypertension (angiotensin-I converting enzyme) and the key enzyme of cholesterol metabolism (3-hydroxy-3-methylglutaryl coenzyme A reductase). The latter inhibitory activity was also noticed in SFE extracts although ergosterol and other lipid-like molecules were isolated. Dietary fibers were separated in the third extraction. Therefore, with this sequential extraction procedure bioactive compounds against CVDs can be selectively separated from a single batch of shiitake powder. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:746-755, 2018.

Eritadenine from Edible Mushrooms Inhibits Activity of Angiotensin Converting Enzyme in Vitro

The inhibition of angiotensin converting enzyme (ACE) activity was determined in vitro by mushroom-derived eritadenine (EA), which was analyzed in 11 principal Korean edible mushrooms. EA inhibited ACE activity with 0.091 μM IC50, whereas the IC50 of captopril (CP), which is a reference compound, was 0.025 μM. Kinetic measurements of ACE reaction in the substrate of hippuryl-l-histidyl-l-leucine (HHL) with or without EA revealed that the Vmax (0.0465 O.D/30 min) was unchanged, but the the Km increased from 2.063 to 3.887 mM, indicating that EA competes with HHL for the active site. When EA was analyzed by HPLC, Lentinus edodes with a soft cap contained the highest amount EA (642.8 mg%); however, Phellinus linteus with a hard cap contained the least amount of EA (9.4 mg%). These results indicate that EA was a strong competitive inhibitor for ACE, and edible mushrooms with soft caps contained a significant amount of EA.

Water-Soluble Compounds from Lentinula edodes Influencing the HMG-CoA Reductase Activity and the Expression of Genes Involved in the Cholesterol Metabolism

A water extract from Lentinula edodes (LWE) showed HMG-CoA reductase inhibitory activity but contained no statins. NMR indicated the presence of water-soluble α- and β-glucans and fucomannogalactans. Fractions containing derivatives of these polysaccharides with molecular weight down to approximately 1 kDa still retained their inhibitory activity. Once digested LWE was applied to Caco2 in transport experiments, no significant effect was noticed on the modulation of cholesterol-related gene expression. But, when the lower compartment of the Caco2 monolayer was applied to HepG2, some genes were modulated (after 24 h). LWE was also administrated to normo- and hypercholesterolemic mice, and no significant lowering of serum cholesterol levels was observed; but reduction of triglycerides in liver was observed. However, LWE supplementation modulated the transcriptional profile of some genes involved in the cholesterol metabolism similarly to simvastatin, suggesting that it could hold potential as a hypolipidemic/hypocholesterolemic extract, although further dose-dependent studies should be carried out.

Plasma Cholesterol-Lowering Activity of Lard Functionalized with Mushroom Extracts Is Independent of Niemann-Pick C1-like 1 Protein and ABC Sterol Transporter Gene Expression in Hypercholesterolemic Mice

Interest in food matrices supplemented with mushrooms as hypocholesterolemic functional foods is increasing. This study was to (i) investigate the hypocholesterolemic activity of lard functionalized with mushroom extracts (LF) including fungal β-glucans, water-soluble polysaccharides, or ergosterol and (ii) examine the LF influence on transcriptional mechanisms involved in cholesterol metabolism. mRNA levels of 17 cholesterol-related genes were evaluated in jejunum, cecum, and liver of high cholesterol-fed mice. The four tested LFs decreased plasma cholesterol by 22-42%, HDLc by 18-40%, and LDLc by 27-51%, and two of them increased mRNA levels of jejunal Npc1l1 and Abcg5 and hepatic Npc1l1. mRNA levels of other cholesterol-related genes were unchanged. These findings suggest that LF may have potential as a dietary supplement for counteracting diet-induced hypercholesterolemia and could be a source for the development of novel cholesterol-lowering functional foods. However, the cholesterol-lowering effect was unrelated to transcriptional changes, suggesting that post-transcriptional mechanisms could be involved.

A high-dose Shiitake mushroom increases hepatic accumulation of triacylglycerol in rats fed a high-fat diet: underlying mechanism

Shiitake mushroom have been shown to have health benefits including lowering plasma lipids and preventing body weight gain. However, their underlying mechanisms are largely unknown. The study aim was to assess the potential underlying mechanism of Shiitake mushrooms in lowering plasma triacylglycerol (TAG) in rats fed a high fat diet (HFD). Forty Wistar rats were divided into control group were given HFD and treatment group were fed HFD, enriched with Shiitake mushroom powder at a low dose (LD-M): 0.7%, medium dose (MD-M): 2%, or high dose (HD-M): 6% (wt:wt) for six weeks. Diets were isocaloric containing ~50% energy from fat. After six weeks' dietary intervention, the rats were sacrificed, and blood and tissue samples were collected. The HD-M group showed a significantly higher ratio of liver weight to 100 g body weight (p < 0.05), a more severe hepatic steatosis marker, such as hepatocyte ballooning (p < 0.0001), and more liver triacylglycerol content than LD-M and MD-M (p < 0.05). HD-M also showed a significantly decreased ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) compared to HFD (p < 0.05), however, there were no differences compared to HD-M and MD-M. Our results also showed a positive association between the dosage, liver TAG, and liver ballooning histology. A negative association was found between the mushroom dosage and the ratio of liver PC to PE. This study showed the mechanism of how high-dose Shiitake mushroom (HD-M) prevents obesity by increasing TAG accumulation in the liver, rather than adipose tissue.

Lentinus edodes promotes fat removal in hypercholesterolemic mice

Lentinus (L.) edodes (shiitake mushroom) is used as a traditional medicine in Asia. One of the components of L. edodes, eritadenine (an adenosine analog alkaloid), has been shown to reduce cholesterol levels. The hypocholesterolemic action of eritadenine appears to be achieved through the modification of hepatic phospholipid metabolism. In the present study, the effects of L. edodes in a mouse model of hypercholesterolemia were investigated. Hypercholesterolemia was induced by the consumption of a high-fat diet (HFD). The animals were divided into six groups, which were fed a normal diet, HFD alone, HFD containing eritadenine [10 mg/kg of body weight (BW)] or HFD with 5, 10 or 20% L. edodes, respectively, for 4 weeks (from 5 to 9 weeks of age). The mice in the six groups had similar BW gains. Total serum cholesterol (T-CHO), low-density lipoprotein (LDL) and triglyceride (TG) levels were increased in the HFD-fed group compared with those in the normal diet group. However, the levels of high-density lipoprotein (HDL) were not significantly altered. In mice treated with L. edodes (5, 10 or 20%), the T-CHO, LDL and TG serum levels were reduced in a dose-dependent manner. The mRNA expression of cholesterol 7-α-hydroxylase 1 (CYP7A1) was decreased in hypercholesterolemic mice and increased by eritadenine and L. edodes (5, 10 and 20%) supplementation. In liver tissues, it was observed that lipid accumulation was reduced by treatment with eritadenine and L. edodes. In addition, it was revealed that the formation of atherosclerotic plaques due to the HFD was also suppressed by eritadenine and L. edodes. The results of the study indicated that the consumption of an HFD may inhibit CYP7A1 expression in the liver by increasing serum T-CHO, LDL and TG levels. L. edodes may help regulate lipid metabolism, suggesting that this fungus ameliorates hypercholesterolemia in mice by regulating CYP7A1 expression in the liver.

Comparative studies on chemical parameters and antioxidant properties of stipes and caps of shiitake mushroom as affected by different drying methods

BACKGROUND

Shiitake, the second most cultivated mushroom, is famous for its high nutritional value and medicinal properties. In this study, various chemical parameters and antioxidant properties of caps and stipes of shiitake mushroom dried by different methods (freeze-drying, shade drying and hot air drying) were comparatively investigated by spectrophotometric assays, high-performance liquid chromatography, 1,1'-diphenyl-2-picrylhydrazyl assay, ferric reducing power assay and lipid peroxidation inhibition assay.

RESULTS

The contents of amino acids, neutral sugar and total phenolics in stipes were higher than those in caps of shiitake, while caps showed advantages in terms of their contents of protein and eritadenine. The chemical parameters and antioxidant activities of shiitake were significantly affected by the drying method used.

CONCLUSION

The contents of total phenolics, amino acids and neutral sugar in stipes were higher than those in caps of shiitake, which suggested that stipes were more nutritional than caps in some respects. Hot air drying at 50 °C resulted in high total phenolic, amino acid, uronic acid and neutral sugar contents and antioxidant activities, which could be useful for the application of shiitake and related products in the food industry.

Preventive effects of Lentinus edodes on homocysteinemia in mice

Homocysteinemia is associated with cardiovascular and neuronal degenerative diseases. Deficiencies of the B vitamins lead to high homocysteine serum levels. Lentinus edodes (L. edodes) is also known as the Shiitake mushroom and may have beneficial effects on vascular and lipid metabolic diseases, including hypertension, homocysteinemia and lipidemia. In this study, we induced a homocysteinemia-like condition in mice by the administration of a folate- and vitamin B12-deficient diet and evaluated the effect of L. edodes on the homocysteinemia-like condition. Homocysteinemia was induced by the administration of a diet deficient in folate and vitamin B12 (DFV) for 6 weeks to mice aged 4–10 weeks. The homocysteinemic mice were treated with L. edodes flour (5, 10 and 20%), eritadenine (10 mg/kg) or DFV only (negative control) for 2 weeks. The DFV induced a significant increase in serum homocysteine levels. The increased homocysteine serum levels were reduced by eritadenine and L. edodes flour (5, 10 and 20%). Hepatic levels of S-adenosyl-L-homocysteine hydrolase (SAH) were significantly higher under DFV administration and the elevated SAH levels were reduced by treatment with L. edodes in a dose-dependent manner. The mRNA expression levels of DNA methyl transferases, DNMT1 and DNMT3a, were reduced in the DFV group, and the reduced levels of DNMT1 and DNMT3a mRNA expression were recovered in the eritadenine and L. edodes (5, 10 and 20%) groups. These results suggest that components of L. edodes, including eritadenine may have beneficial effects on hyperhomocysteinemia and its therapeutic effects may be involved in the regulation of DNA methylation-related genes in mice.

Isolation of natural products by ion-exchange methods

The primary goal of many natural products chemists is to extract, isolate, and characterize specific analytes from complex plant, animal, microbial, and food matrices. To achieve this goal, they rely considerably on highly sophisticated and highly hyphenated modern instrumentation. Yet, the vast majority of modern instrumentation typically found in the laboratories of natural products chemists is founded on the simple principles of intermolecular forces to achieve separation. Ion-exchange chromatography (IEC) is, at heart, the most fundamental, and strongest, of these interactions and is considered a relatively inexpensive and effective medium in which to "clean-up" a sample. Additionally, IEC offers high recoveries of key analytes and offers the ability to modify the stationary and mobile phases in order to selectively "catch and release" compounds of interest.

Dietary Shiitake Mushroom (Lentinus edodes) Prevents Fat Deposition and Lowers Triglyceride in Rats Fed a High-Fat Diet

High-fat diet (HFD) induces obesity. This study examined the effects of Shiitake mushroom on the prevention of alterations of plasma lipid profiles, fat deposition, energy efficiency, and body fat index induced by HFD. Rats were given a low, medium, and high (7, 20, 60 g/kg = LD-M, MD-M, HD-M) Shiitake mushroom powder in their high-fat (50% in kcal) diets for 6 weeks. The results showed that the rats on the HD-M diet had the lowest body weight gain compared to MD-M and LD-M groups (P < 0.05). The total fat deposition was significantly lower (-35%, P < 0.05) in rats fed an HD-M diet than that of HFD group. Interestingly, plasma triacylglycerol (TAG) level was significantly lower (-55%, P < 0.05) in rats on HD-M than HFD. This study also revealed the existence of negative correlations between the amount of Shiitake mushroom supplementation and body weight gain, plasma TAG, and total fat masses.

Production of the bioactive compound eritadenine by submerged cultivation of shiitake (Lentinus edodes) mycelia

Fruit bodies and mycelia of shiitake mushroom ( Lentinus edodes) have been shown to contain the cholesterol-reducing compound eritadenine, 2( R),3( R)-dihydroxy-4-(9-adenyl)butyric acid. In the search for a production method for eritadenine, shiitake mycelia were investigated in the present study. The mycelia were cultivated both in shake flasks and in bioreactors, to investigate the effects of pH, stirring rate, and reactor type on the production and distribution of eritadenine. Both the biomass and the culture broth were examined for their eritadenine content. In the shake flasks, the final concentration of eritadenine was 1.76 mg/L and eritadenine was equally distributed between the mycelia and the growth media. In the bioreactors, the shiitake mycelia were found to contain eritadenine in relatively low levels, whereas the majority, 90.6-98.9%, was detected in the growth media. Applying a stirring rate of 250 rpm during bioreactor cultivation resulted in the highest eritadenine concentrations: 10.23 mg/L when the pH was uncontrolled and 9.59 mg/L when the pH was controlled at 5.7. Reducing the stirring rate to 50 rpm resulted in a decreased eritadenine concentration, both at pH 5.7 (5.25 mg/L) and when pH was not controlled (5.50 mg/L). The mycelia in the shake flask cultures appeared as macroscopic aggregates, whereas mycelia cultivated in bioreactors grew more as freely dispersed filaments. This study demonstrates for the first time the extra- and intracellular distribution of eritadenine produced by shiitake mycelial culture and the influence of reactor conditions on the mycelial morphology and eritadenine concentrations.