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Paenibacillus campinanesis BL11 xylanase assisted ECF bleaching for hardwood kraft pulp
No full text微生物在各種不同的環境下，有著相當豐富的多樣性。而微生物能產生在高溫或強鹼下具有活性的酵素，這些酵素在工業上有著強大的應用潛力。耐高溫之強鹼木聚醣酶，能協助去除紙漿表面木質素，有效減少氯系漂白劑使用量。本研究針對由漂前黑液中分離之耐高溫強鹼Paenibacillus campinanesis BL11菌株，進行木聚醣酶誘導，以找出生產的最適條件，並將之應用於硫酸鹽闊葉樹紙漿無元素氯漂白製程，以期探討其減少漂白藥劑使用量之效益。
Paenibacillus campinanesis BL11，能生存在pH 11.5之稀釋硫酸鹽紙漿黑液中。且其木聚醣酶在pH 8，溫度60oC環境下，木聚醣酶熱穩定性可達4 小時。基質誘導結果顯示，以1 % 木聚醣 (Birchwood xylan) 與1 % 酵母抽出物(Yeast extract)，溫度37oC，pH 8之液態培養基培養2天能獲得最大酵素活性14.3 IU/ml；為開發廉價生產酵素方式，以不同比例之碳源米殼 (Re husk)、米糠(Rice bran) 與氮源硫酸銨((NH4)2SO4)、尿素(Urea)、大豆粉(Soy bean powder)、玉米浸漬液(Corn steep liquor)進行基質誘導，其中以2 %米殼與0.5 %米糠培養8天也能得到較佳活性12 IU/ml之木聚醣酶。
本試驗進行木聚醣酶輔助無元素氯漂白(OXDED)，分析全漂漿化學紙漿性質，結果顯示氧漂後硫酸鹽紙漿以木聚醣酶處理之最佳條件以pH 8，50oC，活性3 IU/g o.d.p.處理，反應3 小時，能改善黏度與白度。
由分析XDEDD與OXDEDD全漂漿化學性質來看，木聚醣酶處理可以減少二氧化氯使用量，提升紙漿白度與黏度，以氧漂漿提升效果較明顯。於相同白度下，木聚醣酶處理使氧漂前與氧漂後紙漿漂白二氧化氯使用量各降低9.6、14.6 %；黏度分別增加6.0-6.5%、5.6-6.1 %。
就XDEDD與OXDEDD全漂漿物理性質而言，木聚醣酶處理可以改善物理性質，而氧漂前與氧漂後紙漿結果相近。木聚醣酶處理使抗撕指數各增加0-11、0-10 %。破裂指數分別增加0-18、0-26 %，抗張指數各降低0-17、8-21 %。
綜合以上所述，木聚醣酶助漂能在不影響目標白度下，有效減少二氧化氯使用量，並實証微生物多樣性在工業上強大的應用潛力。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.Index
Page
Index ………………………………………………………………………….. I
Table index …………………………………………………………………. IV
Figure index …………………………………………………………………. V
中文摘要 …………………………………………………………………… VII
Abstract ........................................................................................................... IX
I Introduction ………………………………………………………………. 1
II Literature reviews ……………………………………………………….. 4
2.1 Potential of Biodiversity utilization …………………………...…….… 4
2.2 Developing of bleaching technology ………………………………….. 5
2.3 Prebleaching with xylanase …………………………………………… 6
2.3.1 Origin of xylanase in bleaching …………………………………... 6
2.3.2 Proposed mechanism of xylanase aided bleaching ……………….. 7
2.3.3 Factors affecting treatment efficiency …………………………... 10
2.3.4 Effect on chemical requirements ………………………………... 11
2.3.5 Effect on pulp properties ………………………………………... 12
2.3.6 Effect on bleaching effluents .…………………………………… 13
III Objectives ……………………………………………………………... 14
IV Material and Methods …………………………………………………. 15
4.1 Strain ..................................................................................................... 15
4.2 Media ……………………………………………………………….... 16
4.3 Cell growth curve ……………………………………………………. 16
4.4 Medium optimization ………………………………………………… 17
4.5 Cultivation pH and temperature ………………………..…………….. 17
4.6 Thermal stability ……………………………………………………... 18
4.7 Enzyme activity …………………………………………..………….. 18
4.8 Pulp sources ………………………………………………………….. 19
4.9 Xylanase pretreatment ……………………………………………….. 20
4.10 Conditions in bleaching …………………………………………...... 21
4.11 Analytical techniques .......................................................................... 24
4.12 Hand sheet properties ………………………………………………. 24
V Results and Discussions …………………………………………...…… 27
5.1 Xylanase production by BL11 ……………………………………….. 27
5.1.1 Growth curve of strain BL11 ……………………………………. 27
5.1.2 Effect of culture temperature and pH conditions ………………... 28
5.1.3 Effect of carbon and nitrogen sources …………………………... 29
5.1.4 Temperature stability of the xylanase …………………..……….. 32
5.2 Effect of xylanase dosage ……………………………………………. 33
5.3 Effect of xylanase treating time …………………………………...…. 34
5.4 Effect of Active chlorine multiple ……………………………….…... 35
5.4.1 Effect of xylanase on viscosity ……………………………..…… 36
5.4.2 Effect of xylanase on kappa number …………………………..... 37
5.4.3 Effect of xylanase on brightness …………………………..…….. 37
5.4.4 Saving of xylanase on chlorine dioxide …………………...…….. 38
5.5 OXDEDD bleaching …………………………………….…....……… 41
5.5.1 Effect on chemical properties of full beached pulp …..…………. 41
5.5.2 Effect on sheet properties of full beached pulp …………....……. 43
5.6 XDEDD bleaching ……………………….…………………...……… 51
5.6.1 Effect on chemical properties of full beached .pulp ………...…... 51
5.6.2 Effect on sheet properties of full beached pulp …………………. 53
VI Conclusions ……...………..……………...………...………....………. 61
VII References ………………………………………….……….......……. 6
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