Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Microbiology

Egypt faces a high population growth rate nowadays, which demands for an increase in agricultural production efficiency. Consequently, agricultural field residues will increase. Rice straw is one of the main agriculture residues in Egypt. So this study was performed on rice straw as a resource for production of bioethanol. In a series of laboratory experiments, rice straw was pretreated with sodium hydroxide followed by biological treatments for bioethanol production. Both Aspergillus niger NRRL-3 and Trichoderma reesei NRRL-11460 were successfully grown on either cellulose, hemicellulose or holocellulose, byproducts of rice straw hydrolysis. Appreciable amounts of some extracellular enzymes were produced in these very special cultivating media. Among tested enzymes, xylanase was produced in the highest quantity (40.54 IU ml-1), while carboxymethyl cellulase ranked second (3.35 IU ml-1). Holocellulose seemed the pioneer byproduct supporting the enzyme production followed by cellulose, while hemicellulose was the inferior in this respect. Apart from substrate and enzyme type, the fungus T. ressei overcame A. niger for the enzyme formation. The enzymatic activity of introduced inocula obviously reflected on producing sugar pools. Compared to others, T. reesei acted more actively, where the produced reducing sugars could be arranged in the descending order: 2.62 mg ml-1 (T. ressei) > 2.52 mg ml-1 (A. niger + T. ressei) > 1.10 mg ml-1(A. niger).The optimal level of reducing sugars was scored at 8th day-interval in hollocellulose -amended fungal culture medium, the respective quantities of 22.90, 20.30 and 13.22 were produced in the presence of T. reesei, mixed inoculum and A. niger. Raising the ammonium sulphate over the recommended level in fungal culture medium significantly stimulated sugar production

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