Dynamic changes in the mineral composition within the fruiting body of Volvariella volvacea bull ex Fr. singer from the Philippines.
Mushrooms are generally terrestrial saprobic macrofungi which derived their nutrients from decomposing organic substrates of plants or animal origin. Others which are ectomycorrhizal species have symbiotic relationship with the roots of living trees while very limited species may have synergistic interaction with insects. Saprobic type of mushrooms depending on their enzyme system and the organic substrates they attack may be considered as either leaf litter decomposing or wood rotting.
Edible mushrooms have been regarded as excellent sources of culinary ingredients in the different parts of the world. A number of species are grown commercially while most of the species are still being hunted in the wild by mushroom gatherers, enthusiasts and researchers. One of the most preferred by mushroom aficionados particularly in the tropical and subtropical regions is Volvariella volvacea, an example of a leaf litter decomposing mushroom. V. volvacea which is the most popular mushroom in the Philippines is traditionally regarded as culinary ingredient due to its texture and strong aroma. It is locally called as uong by the Ilocanos, kabute payong/dayami by the Tagalogs and kuat by the Pampangos. Filipinos traditionally consumed this species as part of their viand. Recently, it was reported to be a nutraceutical mushroom due to its medicinal attributes . Being cellulolytic, this mushroom usually grows in the wild on piles of decomposing rice straw, banana leaves, water lily or in any substrates rich in organic matter while others grow on lawns, meadow and fallen logs. During the onset of rainy season, wild edible mushrooms together with their poisonous counterparts usually emerge from their substratum . Community dwellers usually go out in the field in search of wild V. volvacea on rice straw barn or piles of dried banana leaves. Mushrooms in general are known to accumulate macro and micro elements which may be absorbed from the substratum or may be inherently present in their thalli which ultimately bio magnify in the fruiting bodies. In this paper, we describe the dynamic changes in the mineral composition of the fruiting bodies of the wild species of V. volvacea in our desire to provide baseline data regarding the mineral composition of our wild edible species of mushrooms in the Philippines.
MATERIALS AND METHODS
Collection of Samples:
Naturally growing stage 3 (emergence of the pileus) samples of fruiting bodies of V. volvacea were collected from a dumping site of household wastes in Sapang Kawayan, Science City of Munoz, Nueva Ecija, Philippines in July 2015. Fruiting body (Fig 1) was divided into several sections starting from the substratum and each section was marked as follows: A -soil, B--volva, C--stipe, 10 mm from the substratum, D--stipe, 20 mm from the substratum, E--stipe, 30 mm from the substratum, F--stipe, 40 mm from the substratum, G--stipe, 50 mm from the substratum, H--stipe, 60 mm from the substratum, I-stipe, 70 mm from the substratum, J--pileus at the center of the stipe, K--10 mm away from the center of the pileus, L--20 mm away from the center of the pileus, M--margin of the pileus. Fruiting bodies were air dried at 29[degrees]C prior to mineral analysis.
Analysis of Mineral Composition:
For the determination of minerals, the air-dried fruiting bodies were subjected to elemental analysis using Thermo EDX System (Noran System 6, Ultra Dry, 10mm2 SDD crystal, 129eV resolution, NORVAR window, LN2-Free Type Detector) installed in Hitachi SU1510 Scanning Electron Microscope.
RESULTS AND DISCUSSION
Mushrooms are excellent uptakers of any elements available in the substrates in which they are associated. This has been previously demonstrated on some mushrooms such as Pleurotus pulmonarius and Agaricus bisporus [3, 4, 5, 6]. Due to this inherent characteristic of mushrooms, elements are absorbed and become ultimately integrated in the system of mushroom. V. volvacea is a type of edible mushroom that has a volva which encapsulates the immature stipe and pileus at the early stage of fruiting body development. The volva ultimately ruptures that freely liberates the elongated stipe and pileus. In this investigation, the dynamic changes in the mineral composition within the naturally growing stage 3 (emergence of the pileus) of V. volvacea which was obtained from a dumping site of household wastes was demonstrated (Fig 1).
V. volvacea being a cellulolytic mushroom is a leaf litter decomposing mushroom that usually grows on decomposing piles of agro-industrial and forestry wastes . As shown in Fig 2, eleven elements were detected and are distributed within the fruiting body. These elements include Ca, Cl, Fe, K, Mg, Na, P, S, Si, Ti and Mn. Among these elements, Mn, S, and Cl were not detected in the soil which implies that these elements are inherently present in the fruiting body of V. volvacea. However, Mn was only located in the volva while Ti was only detected in the soil but not in any part of the fruiting body. Most of the elements are translocated in the different parts within the fruiting body. Minerals present in the substrate are taken up by growing mycelia and translocated to the sporophore . Ca, Fe, Mg, Na, P, Si were detected in the soil, stipe and pileus but absent in the volva. Moreover, Cl, K, Mg, Na, and S were present in all parts of the stipe regardless of the distance from the substratum. On the other hand, Cl, K, Na, P, and S were detected in all parts of the pileus regardless of the distance from center. Among the elements, K was the most abundant. Elements are concentrated in the stipe with at least 10 elements and in the pileus with at least 8 elements. Volva contained the least number of elements which only includes Cl, K, and Mn.
Mushrooms are good sources of minerals  and other nutraceuticals [9, 10, 11, 12]. In human, some elements in small amount are needed for normal functioning of the body which includes Ca, P, S, K, Na, Cl, Mg, Cu, I, Mn, Fe Zn, Se, Co, Cr, and Mo. In the present study, nine elements were found present in the fruiting body of V. volvacea namely; Ca, P, S, K, Na, Cl, Mn, Mg, and Fe. These important minerals were also present in other mushrooms. For instances, Laetiporus suphureus strain MFLUCC12-0546 from Northern Thailand contain Fe, Zn, Mg, Cu, Na, Ca, and Mg  while Termitomyces sp, Russula sp, Pleurotus tuber-regium possess K, Mg, Na, Mn, Fe, Cu, Zn, and P . With this ability of mushrooms to uptake minerals from the substrate, some studies evaluated the translocation of minerals and its effect on the production and functional activity of mushroom. Yokota et al.  found that iron translocation increased the ash and protein, reduced antioxidant activity, and enhanced aroma and flavor characteristics of Pleurotus ostreatus. Thus, minerals can be used as supplements in the substrate to enhance the fruiting body production and nutritional values of mushrooms.
[FIGURE 1 OMITTED]
Legend: A -soil, B--volva, C--stipe, 10 mm from the substratum, D--stipe, 20 mm from the substratum, Estipe, 30 mm from the substratum, F--stipe, 40 mm from the substratum, G--stipe, 50 mm from the substratum, H--stipe, 60 mm from the substratum, I-stipe, 70 mm from the substratum, J--pileus at the center of the stipe, K10 mm away from the center of the pileus, L--20 mm away from the center of the pileus, M--margin of the pileus
[FIGURE 2 OMITTED]
The partially opened fruiting body of V. volvacea contains 11 elements with potassium as the most ubiquitous. Most of the elements are concentrated in the stipe of the fruiting body. The distribution of the different elements within the fruiting body is very dynamic.
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(1) Michael R. Umagat, (2,4) Rich Milton R. Dulay, (3) John Closter F. Olivo, (4) Marcelino D. Abon, (4) Bismark E. Francisco, (2,4) Sofronio P. Kalaw and (1,2,4) Renato G. Reyes
(1) Electron Microscopy Laboratory, (2) Department of Biological Sciences and (3) Department of Statistics, College of Arts and Sciences, (4) Center for Tropical Mushroom Research and Development, Central Luzon State University, Science City of Munoz, Nueva Ecija, Philippines
Address For Correspondence:
Michael R. Umagat, Electron Microscopy Laboratory, Department of Biological Sciences, College of Arts and Science, Central Luzon State University, Science City of Munoz, Nueva Ecija 3120, Philippines.
Tel: 63-44-4560-9405; E-mail: firstname.lastname@example.org
This work is licensed under the Creative Commons Attribution International License (CC BY).
Received 22 March 2016; Accepted 28 May 2016; Available online 12 June 2016
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|Author:||Umagat, Michael R.; Dulay, Rich Milton R.; Olivo, John Closter F.; Abon, Marcelino D.; Francisco, Bi|
|Publication:||Advances in Environmental Biology|
|Date:||May 1, 2016|
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