الفهرس 
Biology of mushroomsOnly 14 pages are availabe for public view
Abstract
The purpose of this study was to resolve the question of how high Se concentrations affect biomass production, defining the highest tolerant Se dose for mycelial growth of Pleurotus ostreatus, select the optimum growth condition for biomass production and selenium accumulation, Oyster mushroom (Pleurotus ostreatus) was also cultivated on different carbohydrate substrates as well as the capacity of Se absorption and accumulation in Pleurotus ostreatus.
The fungi species used in this research were isolated from sawdust by dump-site at Somosta village, Assiut Western Desert Road, Egypt. By use mycological identification keys and taxonomic description. The fungal specie isolated namely: Pleurotus ostreatus.
The obtained result can be summarized as follows:
1. Growth rate and biomass production of Pleurotus strain in PDA and two different fermentation media indicate that higher growth rate 4.3 ±0.03 cm/day give by the media which consists of (g/L); glucose 30g, yeast extract 3g, peptone 2g, KH2PO4 0.6g, MgSO4 • 7H2O 0.4g, vitamin B10.01 g l-1, 0.50 g ampicillin, 15 g agar; the initial pH of the medium was adjusted to 6.5.
2. The carbon sources type and concentration had significant effect on mycelial biomass production. When the cells were grown in the glucose as carbon source at 30 g/l, the mycelial biomass reached their highest level, which give (11.48) g/100ml and (1.83) g/100ml as fresh and dry weight respectively. The mycelium of Pleurotus ostreatus grew optimally at a temperature of 250C and pH of 6.5.
3. comparison between five growth media give that the most suitable media for mushroom growth and biomass production was corn flour extracts and glucose which give 12.62 g/100ml, 1.625 g/100ml as fresh and dry weight respectively and biological efficiency 3.15 % then the fermentation media witch give 12.19 g/100ml, 1.57 g/100ml as fresh and dry weight respectively and biological efficiency 3.05% follow by rice powder extract and glucose. The lower biomass obtain from rice powder extract witch give 10.93 g/100ml , 1.45g/100ml as fresh and dry weight respectively and biological efficiency 2.73% .These results suggest that a combination of corn flour extract and glucose had complementary effects in promoting the cell growth of Pleurotus ostreatus.
4. The effects of different concentration of inorganic selenium supplements (Na2SeO3) in all media biomass production decreased as Se concentration increased. The MIC of Se was determined to be 10.0 ppm /L.
5. In fermentation medium, Biomass production decreased from 12.13 g L−1 and 1.58 g L−1 as fresh weight and dry weight respectively with biological efficiency 1.52% in the control to 6.25g L−1 and 0.74g L−1 as fresh weight and dry weight respectively with biological efficiency 0.78% at an selenium concentration of 8.0 ppm L−1, while production was completely inhibited at a concentration of 10.0 ppm L−1.
6. In corn flour extract medium the biomass decreased from 11.49g L−1 and 1.53g L−1 as fresh weight and dry weight respectively in the control with biological efficiency 1.45% to 5.13 and 0.65 g L−1 as fresh weight and dry weight respectively with biological efficiency 0.64% at an selenium concentration of 8.0 ppm L−1, while production was completely inhibited at a concentration of 10.0 ppm L−1.
7. In rice powder extract medium biomass production decreased as Se concentration increased. Thus, biomass decreased from 10.84 and 1.45 g L−1 as fresh weight and dry weight respectively in the control with biological efficiency 1.35% to 5.01 and 0.61 g L−1 as fresh weight and dry weight respectively with biological efficiency 0.62% at an selenium concentration of 8.0 ppm L−1, while production was completely inhibited at a concentration of 10.0 ppm L−1..
8. In Corn flour glucose extract medium, Biomass production decreased from 12.62 and 1.63 g L−1 as fresh weight and dry weight respectively in the control with biological efficiency 3.15% to 7.15 and 0.76g L−1 as fresh weight and dry weight respectively with biological efficiency 1.78% at an selenium concentration of 8.0 ppm L−1, while production was completely inhibited at a concentration of 10.0 ppm L−1 .
9. In Rice powder glucose extract medium, Production decreased from 11.85 and 1.53 g L−1 as fresh weight and dry weight respectively in the control with biological efficiency 2.96 % to 6.53 and 0.68g L−1 as fresh weight and dry weight respectively with biological efficiency 1.63% at an selenium concentration of 8.0 ppmL−1, while production was completely inhibited at a concentration of 10.0 ppm L−1
10. Effect of selenium concentration in selenium absorption, the reactions of selenium with potassium iodide in acidic medium liberate iodine. The librated iodine bleaches the violet colour of azure B, which is measured at 644 nm. This decrease in absorbance is directly proportional to selenium concentration.
11. In all media type, the Na2SeO3 was good Se source absorption by mycelium and incorporation of Se compounds in the cell, in investigated Pleurotus strain. By the increased of Se concentration in the medium the selenium concentration increase in mycelium.
12. Among the investigated strain of Pleurotus ostreatus in fermentation medium The Pleurotus ostreatus which was cultivated in the Se-enriched medium with 3.0, 5.5, 6.5, 7.5 ppml—1, respectively, showed high Se concentrations in the mycelium (1.163µgml-1, 1.149µgml-1, 1.172µgml-1 , and 0.963µgml-1 of dry weight, respectively) when compared with the control sample witch give1.199µgml-1.
13. In Corn flour extract medium, The Pleurotus ostreatus which was cultivated in the Se-enriched medium with 3.0, 5.5, 6.5, 7.5 and 8 ppm/l, respectively, showed high Se concentrations in the mycelium (1.005µgml-1, 1.131µgml-1, 1.013µgml-1 , 0.935µgml-1 and 0.968 µgml-1 of dry weight, respectively) with selenium concentration increased in compared with the control sample witch give 1.132µgml-1.
14. In Rice powder extract the strain of Pleurotus ostreatus, The Pleurotus ostreatus which was cultivated in the Se-enriched medium with 3.0, 6.5, 7, ppml—1 and 7.5 ppml—1, respectively, showed high Se concentrations in the mycelium (1µgml-1, 0.972µgml-1, 0.891µgml-1 , 0.999µgml-1 of dry weight, respectively) with selenium concentration increased in compared with the control sample witch give 1.035µgml-1.
15. The effect of media composition in mycelium protein content of Pleurotus ostreatus in three different media by Bradford reaction method was studied. The corn flour medium give maximum protein content 0.172 g/L follow by fermentation media witch give 0.169 g/L and the rice powder extract media was the lower protein content witch give 0.153g/L.