الفهرس 
Heavy metals in the environmentOnly 14 pages are availabe for public view
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Abstract
1- The objective of the present investigation is to isolate and identify cadmium and chromium tolerance fungi from different polluted habitats and trying to know their optimum growth conditions in order to improve their tolerance for further application in the recovery of both metals from contaminated environment and using them for wastewater treatment. 2- Seventeen fungal species belonging to 7 genera were isolated from different industrial areas. 3- The most frequently isolated fungal species were Curvularia pallescence and Aspergillus fumigatus and exhibited the best tolerant fungal isolates to cadmium and chromium. 4- C. pallescence could tolerate cadmium and chromium in the growth medium up to 400 and 900 mgL-1 respectively, while A. fumigatus could tolerate cadmium and chromium in the growth medium up to 800 and 8000 mgL-1 respectively and above these concentrations both fungi failed to grow completely. 5- The growth of both fungal species was decreased by increasing cadmium and chromium concentrations in the growth medium. 6- The effect of different carbon sources on the fungal growth and metal tolerance indicated that sucrose and glucose were the most optimum carbon source for growth and also for cadmium and chromium tolerance by C. pallescence and A. fumigatus respectively.
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7- The effect of different nitrogen sources on the fungal growth and metal tolerance indicated that sodium nitrate and peptone were the most optimum nitrogen source for growth and cadmium and chromium tolerance by C. pallescence and A. fumigatus respectively. 8- The effect of different pH values on the fungal growth and metal tolerance indicated that the growth of both fungi and cadmium and chromium tolerance was increased with increasing pH value of the growth medium and reaching its maximum value at pH 6 and 5 for C. pallescence and A. fumigatus respectively. 9- The effect of different incubation temperatures on the fungal growth and metal tolerance indicated that the optimum temperature for growth and cadmium and chromium tolerance by C. pallescence and A. fumigatus was 30o. 10- The effect of different carbon/nitrogen ratio indicated that the optimum carbon/nitrogen ratio for growth and cadmium and chromium tolerance by both fungi was 60/2. 11- Total protein, lipids and carbohydrates content of whole mycelia and cell walls of C. pallescence grown in the presence of different cadmium and chromium concentrations were slightly increased at 300 mg CdL-1 and 400mg CrL-1 and then decreased above these concentrations. 12- Chitin content in the isolated cell walls of C. pallescence grown in the presence of different cadmium and chromium concentrations were slightly increased at 100 mg CdL-1 and 200mg CrL-1 and then decreased above these concentrations.
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13- Total protein and lipids content of whole mycelia and cell walls of A. fumigatus grown in the presence of different cadmium and chromium concentrations were slightly increased at 200 mg CdL-1 and 4000mg CrL-1 and then decreased above these concentrations. While, carbohydrates content increased at 500 mg CdL-1 and 6000mg CrL-1 and then decreased above these concentrations. 14- Chitin content in the isolated cell walls of A. fumigatus grown in the presence of different cadmium and chromium concentrations were slightly increased at 400 mg CdL-1 and 4000mg CrL-1 and then decreased above these concentrations. 15- Cadmium and chromium content in the mycelia of C. pallescence and A. fumigatus and their cell walls were increased with increasing both metal concentrations. 16- The biosorption of cadmium and chromium by fresh and dry biomass of C. pallescence and A. fumigatus was affected by several experimental conditions such as pH values, temperature, initial metal concentrations, biomass dosage and contact time. 17- C. pallescence and A. fumigatus biomasses grown in the presence of 200 mg Cd or CrL-1 could rebind different individual metals such as Pb, Cu, Zn, Co and Fe higher than control. 18- The fungal biomasses were treated physically and chemically for increasing their biosorption capacity. The maximum biosorption capacities of Cd and Cr by both fungi were resulted from sodium hydroxide treatment. While, acid treatment showed a decrease in metal uptake. 19- Electron microscopic studies of C. pallescence grown in the presence of both cadmium and chromium revealed that the cell
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wall was highly increased in its thickness also the apperance of electron dense areas in the cytoplasm which may be aggregation of both metal. 20- Electron microscopic studies of A. fumigatus grown in the presence of both cadmium and chromium revealed that cell damage was occurred in the cell wall, mitochondria and vacuoles. It was observed that black dense granules may occurred inside the cytoplasm which may be agregates of both cadmium and chromium granules.