الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 103 |  |  |
| | | from | 103 | | |
Abstract
Cellulose is considerd to be one of the most renewable and abundant energy source on earth as it can be converted into renewable biofuels such as ethanol or butanol, using of nonrenewable fossil fuels lead to environmental problems so it was necessary to introduce an alternative energy sources.Conversion of cellulose into renewable biofuels require cellulases enzymes which used in many industries like cattle feed, pharmaceutical industry, food nutrition, agricultural industries and textile detergent. Many microorganisms like bacteria, fungi and mold are able to produce cellulases, thermotolerant bacteria are good and promising producers of this enzyme, in this study Rhodothermus marinus a thermophilic strain that was previously isolated and identified by by researchers in Bacteriology and Molecular Biology Lab, it was demonstrated for it is cellulytic activity.Physico-chemical parameters was optimized through central composite design ( CCD )to determine the best cultivation conditions for bacterial growth and activity of the cellulase enzyme produced, the optimum temperature, pH and incubation period were estimated by CCD to be 60oC , 7and 6 days respectively. Nitrogen is a primary component of protoplasm and a primary building block of proteins, it has an impact on bacterial growth and cellulase synthesis so six different nitrogen sources were screened using Plackett-Burman design to determine the best nitrogen source that help in increasing activity of cellulase produced and bacterial growth . It was found that malt extract was significant with positive effect for cellulytic activity and yeast extract was significant with positive effect for bacterial growth so yeast extract, malt extract and CMC ( carbon source) were subsequently used to detect the optimum level of each variable by central composite design (CCD) and the optimum cultivation medium carbon and nitrogen source was 10g/l CMC , 2g/l yeast extract, 2 g/l malt extract. Lignocellulosic biomass contains polymers of cellulose, hemicellulose and lignin bound together in a complex structure, chemically pretreatment was made for lignocellulosic biomass as the biomass pretreatment help in fractionating the hemicellulose and lignin contents to reduce the cellulose crystallinity and increase the porosity of the materials for subsequent depolymerization process, The effect of different solid loading (rice straw, wheat bran, sugarcane bagasse, sawdust (soft wood)) on the callulase produced by Rhodothermus marinus was investigated using untreated and treated lignocellulosic biomass which was used in the cultivation medium in replacement of CMC with the same concentration of it (1%),the untreated and pretreated soft wood show no cellulytic activity but treated sugarcane bagasse, rice straw, wheat bran show a good cellulytic activity of a cellulase produced by Rhodothermus marinus. Pretreated rice straw show the highest cellulytic activity, different concentrations of pretreated rice straw were made ( 0.5%, 1%, 3%, 5%), concentration of 5% show the highest cellulytic activity. Therefore, Rhodothermus marinus can be used for cost-efficient cellulase production for bioconversion of lignocellulosic biomass into biofuels.Placket-Burman Design ( PBD) was utilised to screen six minral sources for their effect on the activity of the cellulase produced by Rhodothermus marinus, and it was found that MnSO4 is statistically significant with a negative effect on cellulase activity.It means that activity of cellulase increase in presence of low concentration of MnSO4, then it was determined for the best concentration of it and it was (0.01 g/l)So cultivation medium composition that was optimized to enhance the activity of a cellulase produced by Rhodothermus marinus composed of CMC 10g/l , malt extract 2g/l, yeast extract2g/l, MnSO4. H2O 0.01g/l, KH2PO4 0.5g/l, MgSO4.7H2O 0.5g/l, NaCl 5 g/l.Using rice straw in the cultivation medium by replacing CMC with 5% treated rice straw.