الفهرس 
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Abstract
lignocellulosic materials provide a great source for the production of cellulosic ethanol which is known as second generation biofuel. By using the emerging new technology of biofuel production, lignocellulosic waste materials provide a potential alternative to petroleum-based fuels. Cellulose is the major component of plant biomass and is the most abundant polysaccharide on earth. Cellulolytic microorganisms are widely distributed in diverse environments. Actinomycetes play a key role during composting, degradation lignocellulose, due to their thermo-tolerance and adaptability to extreme environments.
In this study, thermophilic actinomycetes were isolated from agricultural residues compost located at the Faculty of Agriculture, Minia University. Fifteen potential cellulose-degrading actinomycetes that have the ability to grow on two cellulosic carbon sources (CMC and avicel) as sole carbon source were isolated. Their cellulolytic activity was qualitatively determined using Congo red clearing zone assay on both CMC and Avicel. Only isolate no. 15 was able to degrade avicel and had the largest degradation zone on both CMC, therefore it was selected for further study and designated as SH15. It has the ability to degrade agricultural waste (wheat straw, rice straw and bagasse) as a sole carbon source with the highest production of reducing sugar was recorded for rice straw.
Highest growth and cellulase production from the isolated actinomycete SH15 was recorded at 40oC, pH 7.0 and after 6 days of incubation. The highest cellulase activity was obtained at 45oC, pH 7 after 70 minutes of incubation.
The isolated actinomycete was gnomically identified by 16S rRNA gene sequence determination, similarity to known sequences of the 16s ribosomal RNA for bacteria and archaea was determined through BLAST database at the National Centre for Biotechnology Information (NCBI - https://www.ncbi.nlm.nih.gov). A phylogenetic tree was constructed using Neighbor-Joining algorithm based on the 16S rRNA gene to determine the revolutionary relationship between the Streptomyces isolate SH15 and the closely related Streptomyces species. Phylogeny shows that isolate SH15 clusters with Streptomyces griseorubnes. Phenotypic classification of Streptomyces sp. SH15 isolate according the International Streptomycetes Project (ISP) also indicated it perfect similarity with Streptomyces griseorubnes, so the isolated actinomycete SH15 genomically and phenotypically identified to be Streptomyces griseorubnes SH15 strain. Two cellulase encoding genes, SCO1187 and SCO2838, were identified in the genome of Streptomyces coelicolor A3 (has a complete genome sequence) is SCO1187 is 1146 bp long gene that encodes a GH12 putative cellulase, whereas SCO2838 is 999 bp long gene that encodes a GH6 endoglucanase. They were cloned in pET47b (+) expression vector using EcoRI and HindII endonucleases. Induction to their expression in E. coli BL21(DE3) was failed which could be related to many reasons with the in appropriate usage of E. coli as expression host is the strongest. Many cloned streptomyces genes were successfully induced in i Streptomyces lividans as expression host.
One of the goals achieved in this study is the construction of a dichotomous key for species level identification of 485 Streptomyces species according to ISP criteria and other well established taxonomic features.