Paenibacillus campinanesis BL11木聚醣酶應用於闊葉樹硫酸鹽紙漿無元素氯漂白之硏究

Abstract

Microbial diversity is abundant under various environments. Alkaline and thermophilic enzymes from these bacteria are with great potentials for industrial application. Alkali-thermophilic xylanase can assist removing lignin from pulp fiber surfaces and reduce usage of chlorine and related agents. Optimum conditions for xylanase inducement from Paenibacillus campinanesis BL11 was studied by using various conditions and nutrient. Induced xylanase was applied on elemental-chlorine-free (ECF) bleaching for hardwood kraft pulp to investigate its benefit on reducing bleaching agent usage. Growth of Paenibacillus campinanesis BL11 was observed under diluted black liquor, pH 11.5. Activity of its xylanase remained in pH 8, 60oC for 4 hours. The result showed P. campinanesis BL11 can produce high xylanase activity (14.3IU/ml) under alkaline medium with 1 % birchwood xylan and 1 % yeast extract. To develop a low-cost method for xylanase production, P. campinanesis BL11 was cultivated with various carbon and nitrogen source, including rice husk, rice bran, (NH4)2SO4, urea, soy bean powder and corn steep liquor. Results showed the maximum xylanase activity (12 IU/ml) could be achieved with 2 % rice husk and 0.5% soy bean cultivation. For the properties of the full-bleached OXDED pulps, it revealed that the optimum treatment condition for oxygen-delignified pulps was 50oC, 3 h, pH 8, dosage 3 IU/g oven dried pulp. After xylanase treatment, lower kappa number, higher brightness and viscosity were achieved for bleached pulps than control groups. For the properties of both full-bleached XDEDD and OXDDD pulps, it showed xylanase pretreatment could reduce chlorine dioxide usage and improve the pulp brightness and viscosity (significantly observed in the oxygen-delignified pulp). With identical target brightness, XDEDD and OXDEDD sequence make the chlorine dioxide amounts decreased 9.6 %, 14.6 % and increased viscosity by 6.0-6.5, 5.6-6.1 %. From the chemicals properties of both full-bleached XDEDD and OXDDD pulps, it reveals that xylanase pretreatments could enhance the physical properties of pulps. It make the tear index increase by 0-11, 0-10 % , burst index increase by 0-18,0-26 %, tensile index decreased by 0-17, 8-21 %. In summary, pretreatment by xylanase from Paenibacillus campinanesis BL11 could significantly reduce the chlorine bleaching chemicals usage without affecting the target brightness of pulps. Its industrial applicability was validated.