The effect of the operating conditions (temperature, time, pH, enzyme level and pulp consistency) used in the enzymatic step of a XP (Cartazyme-hydrogen peroxide) sequence for bleaching Kraft pulp from bagasse on various properties of the resulting pulp and paper sheet products was studied. The quality of bagasse used, was examined by its yield, brightness, viscosity and the Kappa number. Finally, the quality of paper sheets produced were examined by their brightness, breaking length, burst index and tear index. The total number of experiments required for five independent variables was calculated from N=2k+2k+1 equation, in which k is the number of independent variables. The results of 43 experiments performed, were processed using the MINITAB software suite which provided equations that reproduced the values of the dependent variables with less error. The application of the steepest ascent method has been carefully inserted in the experimental design section the identification of the most suitable conditions for optimizing the values of the dependent variables. Based on the results, using enzyme level 6 (IU/g), temperature 35°C, pH 5 and pulp consistency 12% for 2 hrs. in the enzymatic step provided paper sheets of acceptable quality.

The feasibility of using xylanase enzyme for prebleaching Beech kraft pulp, was investigated. A commercial xylananse from Trichoderma viride was added to pulp at various doses of 25,50 and 100 IU/g pulp for different reaction times of 12,16 and 20 h. Then, the enzyme – treated pulp was bleached in HEH sequences, namely, B1: hypochlorite 2% (1h) + extraction + hypochlorite 0.75% (1h), and B2: hypochlorite 2% (2h) + extraction + hypochlorite 1.5%(2h). The results indicated that enzyme-treated samples wich were bleached with B2 sequences, exhibited lower kappa number, higher brightness and lower yellowness, as scompared to those bleached with B1 sequences. Regardless of bleaching sequences, enzyme treatments using a Xylanase dose of 25 IU/g for 16h, showed the lowest kappa number, the highest brightness and the lowest yellowness. Kappa number, brightness and yellowness of control pulps (B1 and B2 sequences) were 11.2, 46.4 (ISO%), 34.3% and 8.9, 55.4(ISO%), and 29.7% respectively. Whereas, kappa number, brightness and yellowness of enzyme-treated samples using 25 IU/g in 16h bleached with B1 sequences, were 10.21, 27.4(ISO%) and 26.5% and those bleached with B2 sequences, were 7.3 , 65.5(ISO%) and 22.3% respectively. The increase of enzyme dose and reaction time decreased pulp yield. Enzyme-treated samples using a xylanase dose of 25 IU/g in 16h, had a medium level of variation. Therefore, regardless of bleaching sequences, a xylanase dose of 25 IU/g for 16h reaction time, could be suggested as optimal using condition of xylanase.

The effect of commercial xylanase enzyme in prebleaching of bagasse kraft pulp was investigated. Xylanase enzyme from Trichoderma viride was added to pulp at various doses of 5, 10, 25 and 50 IU/g pulp for reaction time 2h and then the enzyme treated pulp was bleached in D1ED2 sequences (using Dioxide chlorine 4, 6, 8, 10%+Alkaline extraction+Dioxide chlorine 2% as active chlorine). The results showed that enzymatic treatment improved brightness and opacity and decreased yellowness, kappa number and revolution of refiner for given freeness of bleached pulp significantly (P<0.01). Maximum of brightness and opacity and minimum of kappa number were related to 25 IU/g pulp treatment, which had about 13.1%, 1.46% and 2.23 unit significant differences in comparison with those of the control sample, respectively. Minimum of yellowness was related to 50 IU/g pulp treatment which had about 7.32% significant difference as compared with control sample. Regard to the obtained results, the 25IU/g pulp treatment could be suggested as optimum treatment.

The effect of using commercial xylanase enzyme in prebleaching of bagasse kraft pulp was investigated. Xylanase enzyme from Trichoderma viride was added to pulp at various doses of 10, 25 and 50 IU/g pulp for reaction time 2h and then the enzyme treated pulp was bleached in ADED sequences (Acid sulfuric +Dioxide chlorine 4, 6, 8, 10% + Alkaline extraction + Dioxide chlorine 2% as available chlorine). The results have shown that with increased dioxide chlorine in D1 bleaching sequence, final brightness of bleached pulp was increased significantly (P<0.01). Furthermore, in the case of treated samples by xylanase enzyme optical properties of bleached pulp such as brightness and opacity were increased significantly (P<0.01). For yellowness, revolution of refiner for distinct pulp freeness and kappa number have shown decreased significantly (P<0.01). Maximum of brightness and minimum of kappa number and yellowness were belong to 25 IU/g pulp treatment that about 10.8, 3.98% and 2.24 unit have difference significantly (P<0.01) as compared with control sample respectively. Maximum of opacity and minimum was belong to 50IU/g pulp treatment that about 3 and 13.24% have difference significantly as compared with control sample respectively. Regardless of obtained results 25IU/g pulp treatment could be selected as optimal treatment.

Background and Objective: Xylan the major portion of the hemicellulose of plant cell walls are heterogeneous polysaccharides. Xylanases (EC:3.2.1.8) are enzymes obtained from different species of microorganisms that degrade the xylosidic linkages of xylan’s backbone producing xylose with other monoresidues. In recent years, xylanases have many application in industry such as paper BIOBLEACHING and oil clearing.Materials and methods: In this study xylanase enzyme was purified from culture supernatant of Bacillus stearothermophilus (ATCC 12980) by ammonium sulfate precipitation, gel filtration on sephadex G- 100 followed by ion exchange chromatography on DEAE-cellulose. Also, the effect of pH and temperature on purified xylanase activity was studied.Results: In DEAE- cellulose column chromatography, three protein peaks F-1a, F-1b and F-1c were appeared. Among these peaks, only F-1b showed xylanase activity and the degree of purification attained 63.09 fold. The specific activity and purification fold of the purified xylanase was 87.7U/mg of protein and 17.45, respectively. The enzyme gave maximum activity against xylan as substrate at pH 7.0 and temperature at 60°C. In paper chromatography xylose was detected as the hydrolysis products of oat- spelt xylan by the xylanase at 16 h. These results indicate that xylanase of Bacillus stearothermophilus (ATCC 12980) was endoxylanase.Conclusion: These data includes, optimal pH and temprature suggested that purified xylanase can be suitable for industrial applications.