الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 136 |  |  |
| | | from | 136 | | |
Abstract
The present work aimed to study bioconversion of some agricultural residues by some lignocellulosic fungi that able to produce some lignocellulytic enzymes. fifteen fungal isolates were isolated from different agricultural residues. The most active fungus in cellulolytic enzyme production under SmF and SSF was Aspergillus niger Cultural conditions for production of cellulolytic enzymes from A.niger showed that the highest production of cellulolytic enzymes was recorded after 4 days of incubation on these types of straws. On the other hand, 40˚С was found to be the optimum incubating temperature for maximum production of these enzymes on wheat straw while on corn and rice straw the highest production of such enzymes were recorded at 30˚С. Also, Maximum enzyme production from A. niger was recorded at pH 5.5 at moderate moisture level about (75%) using 1.0gm of each type of straw. Factors affecting the activity of cellulolytic and xylanolytic enzymes have been investigated and it has been found that the optimum incubation period for maximum activity of cellulase and avicelase with their corresponding substrates was recorded after 75 min and for CMC-ase 60min however, in the case of xylanase, maximum activity was recorded after 30min only. 50˚С was found to be the most suitable temperature for maximum activity of all enzymes. The optimum pH level for cellulase and avicelase was at pH 4.5, for CMC-ase was at pH 4 and for xylanase was at pH 5 using 1.5% of their corresponding substrates. Thermal stability of cellulases and xylanase showed that CMC-ase was the most thermostable enzyme at 50˚С and 70˚С and recorded the highest half life time in the case of wheat straw. By studying the bioconversion rate of the studied straw by enzymes, it has been proved that wheat straw showed the highest rate of bioconversion, while rice straw showed the lowest rate. Then enzymes produced from A. niger under SSF technique using some types of agricultural straw have been used for bio-degrading of delignified samples of rice straw compared with the control sample. Results showed that the alkali pretreated rice straw has a higher rate of bioconversion and higher rate of production of reducing sugars.