Mushroom Biology and Mushroom Products. Sánchez et al. (eds). 2002
UAEM. ISBN968-878-105-3
MYCELIAL GROWTH OF GANODERMA LUCIDUM ON A SELENIUM-ENRICHED MEDIA
M. Stajic1, I. Brceski2, S. Duletic-Lausevic1, T.V. Djermanovic2, J. Vukojevic1 and I. Milenkovic1
1Institute of Botany and Botanical Garden “Jevremovac”, Faculty of Biology, University of Belgrade, Belgrade, Yugoslavia. 2Faculty of Chemistry, University of Belgrade, Belgrade, Yugoslavia. <
ABSTRACT
Ganoderma lucidum is a mushroom with high pharmacological value. About one hundred different kinds of triterpenoids and some polysaccharides can be isolated from its fruiting bodies and mycelia. Some of these compounds have been proven to have anti-tumor and immunostimulating properties. One of the most important roles of selenium is an antioxidant acting as a cellular protector against free radical oxidative damage. The aim of our research was to investigate the influence of selenium on the growth rate and biomass exchanges of mycelia and the ability of the mycelia to store this microelement when added to the growth medium. The medium used was potato-dextrose agar (PDA). Concentrations of selenium, in the form of sodium selenite, were as follows: 0.3 mg/l, 0.7 mg/l, 1 mg/l, 1.3 mg/l. PDA was used to analyze the growth rate of the mycelia, and the same medium without agar (liquid) was used for measuring mycelial biomass and accumulated selenium. The accumulation of selenium in the mycelia was measured using an atomic absorption spectrophotometer (graphite furnace). Analyzed concentrations of selenium did not show any significant influence on mycelial growth in comparison to the control. The results of selenium accumulation in the mycelia display higher concentrations in hyphae grown on enriched media.
INTRODUCTION
Ganoderma. lucidum has been collected for four thousand years in China and Japan as a symbol of good health, fortune and immortality (Wasser and Weis 1999). This species is a well known and highly regarded medicinal mushroom. Its fruiting bodies contain 51% polysaccharids, 5% proteins, amino acids, polypeptids, vitamins, steroids, sterols, triterpenoids (100 different kinds), lipids, alcaloids, minerals (Mg, Mn, Mo, Ca, Zn, K, Na, Fe, Cu, S, Ge), ergosterol, and the acid protease (Wasser and Weis 1997).
One hundred different kinds of triterpenoids and some polysaccharids isolated from fruiting bodies and mycelia of G. lucidum have antitumor (ganodermic acid T and Z) and immunostimulating activities. This mushroom contains other components which have a curative effect on: hypertension (ganodermic acid B and D), high blood sugar levels (ganoderal A and B glycans) and high blood cholesterol, allergic reactions (ganoderil acid C), etc. (Wasser and Weis 1997). G. lucidum has shown a high degree of activity against Staphyllococcus, Streptococcus species and Bacillus pneumoniae, perhaps because of increased immune system activity and antiviral effects induced by interferon production (Wasser and Weis 1999).
Selenium is a trace element which at nutritional levels has been shown to have numerous anticarcinogenic or preventative effects (against carcinogen-induced breast, colon, liver and skin cancers in animals), but at higher levels it is known to be toxic (Shamberger 1985). In the treatment of healthy persons selenium benefits the physical activity of whole organism, especially heart, kidneys and eyes. It is incorporated into a number of functionally active selenoproteins, including
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Mushroom Biology and Mushroom Products. Sánchez et al. (eds). 2002
UAEM. ISBN968-878-105-3
the enzyme glutathione peroxidase, which acts as a cellular protector against free radical oxidative damage. The amount of selenium available for assimilation by the tissues depends on the form and concentration of the element (Selenit and selenat are forms which are assimilated at the highest level). Selenium deficiency has been linked with numerous diseases, including endemic cardiomyopathy in Se-deficient regions of China and Australia, cancer, muscular dystrophy, malaria and cardiovascular disease (Foster and Sumar 1997).
The aim of our research was to investigate the influence of selenium on the growth rate and biomass changes of mycelia and the ability of the mycelia to store this microelement when added to the growth medium.
MATERIALS AND METHODS
Fruiting bodies of G. lucidum were collected at localities in Serbia. In this experiment a monosporic culture of mycelia was used. The culture was preserved in test tubes on slants of malt agar. Mycelia were cultivated on potato-dextrose agar (PDA) and on the same medium without agar (liquid) (Booth 1971).
Selenium was used in the form of sodium selenite (Na2SeO3). Before sterilization of the PDA, the following concentrations of Se were added : 0.3 mg/l, 0.7 mg/l, 1 mg/l, 1.3 mg/l., and then measured after sterilization The growth rate of mycelia was analyzed. A liquid medium containing the same concentrations of selenium was used to measure the mycelium biomass produced and accumulated selenium.
30 ml of PDA per petri dish was inoculated with G. lucidum, incubated at a room temperature of 202Cand the diameter of colonies were measured daily for 9 days. Two repetitions were performed with each concentration of selenium. The selenium-enriched liquid medium (50 ml and 100 ml per erlenmayer) was inoculated and incubated at room temperature for 28 days. Afterwards the mycelia was filtered, wieghed and dried.
The accumulation of selenium by mycelia was measured using an atomic absorption spectrophotometer (graphite furnace).
RESULTS AND DISCUSSION
The concentration of selenium in the selenium-enriched liquid medium was measured after sterilization and before inoculation as a control (Table 1).
Table 1. Concentration of selenium in liquid medium.
Before sterilization (g/ml) / After sterilization (g/ml)0.3 / 0.447
0.7 / 1.083
1 / 1.168
1.3 / 2.001
The analyzed selenium concentrations did not show any influence on the appearance of colonies, nor on their growth rate, compared to the control. Colonies of G. lucidum were white, dense and looked like carpet. The growth rates were similar, about 1.0 cm/day (Figure 1).
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Mushroom Biology and Mushroom Products. Sánchez et al. (eds). 2002
UAEM. ISBN968-878-105-3
After cultivation in the liquid medium, samples were filtered and fresh mycelia separated and measured. Biomass varied depending on selenium concentrations. Significant differences occurred at selenium concentrations of 1.0 and 1.3 mg/l. At 1.0 mg/l concentration, the biomass yield was the highest, while at a concentration of 1.3 mg a decrease of mycelial biomass was noticeable compared to the control (Figure 2).
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Mushroom Biology and Mushroom Products. Sánchez et al. (eds). 2002
UAEM. ISBN968-878-105-3
The mycelium of G. lucidum cultivated in liquid medium without selenium was found to contain 1.529 g/g selenium dry weight. Past studies have not reported that G. lucidum contains selenium, although many other elements have been found (Wasser and Weis 1997). Adding selenium in liquid medium considerably influenced the final selenium concentration in mycelia, but the concentration was not proportional to the amount of selenium added. Concentrations of selenium in the mycelia varied significantly depending on the concentration of selenium added. Selenium absorption was the highest at 1 mg/g concentration , while at 1.3, a decrease in the selenium concentration was observed (Figure 3).
These results are the first one describing selenium absorption by the mycelium of G. lucidum. In a previous investigation Pleurotus ostreatus cultivated on the same medium and with the same selenium concentrations showed significantly higher absorption of selenium by P. ostreatus mycelium (Stajic et al. 2002).
REFERENCES
Booth, C. 1971. Fungal Culture Media. In: C. Booth (ed.). “Methods in Microbiology” 4. Academic Press, London, New York. 49-94.
Foster, L. and S. Simar. 1997. Selenium in health and disease: a review. Critical Reviews in Food Science and Nutrition. 37(3): 211-228.
Shamberger, R. J. 1985. The genotoxicity of selenium. Mutation research. 154: 29-48.
Stajic, M., I. Milenkovic, I. Brceski, J. Vukojevic and S. Duletic-Lausevic. 2002. Mycelial growth of Pleurotus ostreatus (Jacq.: Fr.) P. Kumm. on the selenium-enriched media. Int. J. Med. Mush. issue N1 (in press).
Wasser, P. S., L.A. Weis and C. Chem. 1997. Medicinal mushroom Ganoderma lucidum-reishi mushroom. In:E. Nero (ed). San Antonio-Haifa-Kiev.
Wasser, P. S. and L. A. Weis. 1999. Medicinal Properties of Substances Occurring in Higher Basidiomycetes Mushrooms: Current Perspectives (Review). Int. J. Med. Mush. 1: 31-62.
Wasser, P. S., L. A. Weis. 1999. General Description of the Most Important Medicinal Higher Basidiomycetes Mushrooms. 1. Int. J. Med. Mush. 1: 351-370.
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