洛阳理工学院毕业设计（论文）

[20]盛清等.香菇脚的成分分析及其产品开发.食品研究与开发，1999，

(4):48一50

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洛阳理工学院毕业设计（论文）

外文资料译文

Mushroom strains able to grow

at high temperatures and low pH values

S.A. Furlan,* L.J. Virmond, D.A. Miers, M. Bonatti, R.M.M. Gern and R. Jonas

Abstract：Seven strains of edible mushrooms were studied with regard to mycelial growth on different growth media and culture conditions. Medium WDA (wheat/dextrose/agar) promoted higher rates of mycelial growth for all the mushrooms investigated. The majority of the strains presented higher growth rates at 30° C, but only Lentinus edodes kept maximum rates at low pH (pH 4.0), followed by Stropharia rugosoannulata and Pleurotus ostreatus (pH 5.0). Absence of light favoured rapid mycelium development in all the strains tested.

Key words: Agricultural wastes, mushrooms, mycelial growth.

Developing countries, such as Brazil, have a predomi-nantly agricultural economy. A prominent characteristic of the agricultural sector is that by-products and wastes greatly exceed the harvestable or marketable compo-nents. These wastes consist largely of lignocellulosic materials, an abundant and renewable source of carbo-hydrates that can be converted into added-value prod-ucts. It is estimated that 60 ′ 10 9 tons of cellulose are generated by photosynthesis each year worldwide, but only about 20% are used for conversion into energy and feed (Tsao 1986). Food and by-products are the indus-try's only current products, but feeds and pharmaceuti-cals are possible products now being studied.Macromycetes and a few other related organisms seem to be the most suitable organisms for the conversion of cellulosics (Kurtzman 1979). The material remaining after the mushroom crop has been harvested can be used as a valuable additive for the soil, increasing

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洛阳理工学院毕业设计（论文）

its potential for the production of further agricultural and horticultural crops.

Although mushrooms have long been appreciated because of their ˉavour, texture or medicinal properties, he recognition of their nutritional importance is recent. Mushrooms have a high content of good quality protein,19±35% (w/w) on dry weight basis, containing all the ssential amino acids. Further- more, mushrooms have a high proportion of unsaturated fatty acids, several vitamins and minerals, have low fat and cholesterol contents and are low in calories.

For colonization of agricultural and forest wastes by mushrooms, it is necessary to ensure the best conditions for growth. Tan & Chang (1989) pointed out that high yields of mushroom fruit bodies of Lentinus edodes have been associated with good mycelial growth. Further-more, Zadrazil (1974), investigating the mycelial growth of Pleurotus ostreatus , reported that higher rates of mycelial growth increase the rate of penetration of the substrate by the fungi. In studies on Pleurotus growth, it was observed that addition of nitrogen during mycelia growth increased the pH, favouring contamination and leading to a decrease in productivity. The present work deals with the selection of mushroom strains able to grow at high temperatures and low pH values, in order to have a successful mycelia growth in tropical regions and to avoid contamination, respectively.

Materials and Methods Microorganisms

Fungal cultures were obtained from DSM (Deutsche Sammlung von Mikrorganismen und Zellkulturen GmbH) and numbered as follows: 1 ± DSM 1655, Stropharia rugosoannulata; 2 ± DSM 1658, Flammulina velutipes; 3 ± DSM 1684, Kuehneromyces mu-tabilis ; 4 ± DSM 1833, Pleurotus ostreatus; 5 ± DSM 1899, Lent-inula (Lentinus) edodes ; 6 ± DSM 3279, Volvariella

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洛阳理工学院毕业设计（论文）

volvacea;7±DSM 4135, Agaricus bitorquis . The strains were maintained at environmental temperature on agar slants and Petri dishes containing potato/dextrose/agar (PDA) medium. Growth Media

Three different growth media were tested: WDA (20 g dextrose,15 g agar/l wheat infusion); PDA (20 g dextrose, 15 g agar/l potato infusion); and MPA (30 g malt extract, 3 g soya peptone,15 g agar/l distilled water). Wheat infusion preparation: 500 g of washed wheat grains were boiled in 1l of water for 10 min and ?ltered through gauze. Potato infusion preparation: 200 g of pricked potato were boiled in 1l of water for 20 min and ?ltered through gauze. The culture media were sterilized in an auto-clave at 1 atm at least for 20 minutes.

Growth Conditions and Evaluation of Mycelial Growth

Cells were grown on agar plates inoculated in the centre with an agar disk (8 mm diameter), containing the mycelium. Based on the literature (Zadrazil 1974; Tan & Chang 1989), rapid mycelia growth on agar plates was the criterion used in our work for strain selection. Growth was evaluated periodically by measur-ing colony radius. The Petri dishes were incubated in absence of light (except for the experiment on light inˉuence). Tempera-tures tested were 20, 25 and 30 ° C, except for strain 6 (30, 35 and 40° C) which presents better growth at higher temperature (Kurtzman & Chang-Ho 1982; Santiago 1983). All strains were tested at different pH values (4.0, 5.0, 5.6 and 6.4). The experi-ments were carried out in triplicate and standard deviations and errors were calculated.

Results and Discussion Growth Medium

Mycelial growth of the different strains was evaluated in the absence of light, at pH 6.4 and 30 ° C, except for strains 2 and 3 which were tested at 25 ° C. Figure 1 shows the global rates of mycelial growth (mm/day) using media

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