本文關(guān)鍵詞：耐堿性纖維素酶的表達(dá)及其對(duì)紙漿改性和機(jī)制研究　出處：《山東大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 耐堿性纖維素酶 耐堿性木聚糖酶 共表達(dá) 紙漿 酶法改性 機(jī)制

【摘要】：由于草漿等紙漿存在濾水性差、強(qiáng)度低等缺點(diǎn),使其應(yīng)用受到限制,一般生產(chǎn)過程中需要對(duì)其進(jìn)行改性以改善濾水和強(qiáng)度性能。與化學(xué)法改性相比,采用纖維素酶(主要是內(nèi)切酶EG)處理對(duì)紙漿改性是一種環(huán)境友好的技術(shù),且已被證明在改善紙漿濾水性,提高成紙強(qiáng)度等方面具有良好效果。由于制漿造紙工藝往往在中、堿性條件下進(jìn)行,這就要求使用的酶能夠在高pH條件下維持酶活性,保證其催化作用有效進(jìn)行。但市場(chǎng)上已有的商品纖維素酶大多為酸性酶,在堿性條件下酶活很低。雖然國內(nèi)外對(duì)堿性纖維素酶的研究正逐漸深入,但目前仍存在很多問題,例如,已有產(chǎn)堿性纖維素酶菌株的產(chǎn)量低、酶系不合理、酶改性機(jī)理尚未完全清楚等。因此,設(shè)法提高堿性纖維素酶產(chǎn)量,合理優(yōu)化酶系,以降低纖維素酶生產(chǎn)成本和提高對(duì)紙漿的改性效果,同時(shí)深入研究酶法改性機(jī)制等,對(duì)促進(jìn)酶在造紙工業(yè)中的應(yīng)用,降低生產(chǎn)成本等具有重要意義�；谝陨媳尘�,本論文在實(shí)驗(yàn)室前期研究基礎(chǔ)上,通過構(gòu)建耐堿性纖維素酶菌株,以希望提高纖維素酶產(chǎn)量;同時(shí)通過構(gòu)建耐堿性纖維素酶與木聚糖酶共表達(dá)菌株,以達(dá)到優(yōu)化改性酶系、提高酶法改性效果的目的;同時(shí)從不同角度研究了紙漿酶法改性的機(jī)制。本論文主要研究?jī)?nèi)容和結(jié)果如下:1.耐堿性纖維素酶的表達(dá)及其對(duì)紙漿改性效果研究為獲得適合紙漿改性用的耐堿性纖維素酶,在實(shí)驗(yàn)室前期研究基礎(chǔ)上,擴(kuò)增來源于特異腐質(zhì)霉的三個(gè)耐堿性內(nèi)切纖維素酶H.EGⅠ,H.EGⅡ,H.EGⅤ的基因,并在畢赤酵母GS115中成功異源表達(dá);同時(shí)在大腸桿菌BL21中成功異源表達(dá)了來源于不同芽孢桿菌的三個(gè)內(nèi)切纖維素酶Y106-EG,z-16-EG及A30-EG。測(cè)定純化后重組耐堿性纖維素酶的性質(zhì),發(fā)現(xiàn)這六種內(nèi)切纖維素酶的最適pH在6.5-7.5左右,最適溫度在50℃-60℃之間,各酶在pH 6.0-8.0條件下放置1h能夠維持60%以上酶活性,其中Y106-EG、z-16-EG和H.EGV在pH 9.0條件下放置1 h可以維持60%以上酶活性。將六種耐堿性內(nèi)切酶應(yīng)用于麥草漿改性,發(fā)現(xiàn)Y106-EG在酶用量?jī)H為0.2 IU/g條件下,與對(duì)照相比,能夠降低12.5%的打漿度,抗張強(qiáng)度指數(shù),耐破指數(shù),撕裂指數(shù)分別提升14.6%、14.3%和10.7%。對(duì)紙漿的改性效果明顯優(yōu)于其它五種耐堿性內(nèi)切葡聚糖酶,顯示出良好的潛在應(yīng)用前景。2.重組菌Y106OE-EG粗酶液對(duì)不同紙漿改性時(shí)的酶處理?xiàng)l件優(yōu)化及與其它酶的協(xié)同作用研究為提高耐堿性纖維素酶Y106-EG的產(chǎn)量,利用基因工程方法,實(shí)現(xiàn)Y106-eg基因的同源過表達(dá),經(jīng)實(shí)驗(yàn)室前期優(yōu)化的發(fā)酵培養(yǎng)基發(fā)酵,所得發(fā)酵液的CMCase酶活達(dá)到8.45 IU/ml,是出發(fā)菌株的8.28倍。利用工程菌Y106OE-EG粗酶液對(duì)楊木CMP(楊木化學(xué)機(jī)械漿),松木CMP(松木化學(xué)機(jī)械漿),麥草CP(麥草化學(xué)漿)進(jìn)行改性研究發(fā)現(xiàn),改性效果依次為麥草CP楊木CMP松木CMP。對(duì)酶法改性時(shí)的酶處理?xiàng)l件(處理溫度、時(shí)間和pH等)進(jìn)行了優(yōu)化,發(fā)現(xiàn)當(dāng)酶用量?jī)H為0.2 IU/g漿,pH 7.0,溫度55 ℃條件下對(duì)麥草漿處理2 h,與未用酶處理的對(duì)照相比,紙漿的抗張指數(shù),耐破指數(shù),撕裂指數(shù)分別增加了15.4%、16.9%和 11.8%。研究了工程菌Y106OE-EG粗酶液與其它酶的協(xié)同改性效果,發(fā)現(xiàn)Y106OE-EG的內(nèi)切纖維素酶與纖維素膨脹因子SWO4的聯(lián)合處理,與單獨(dú)使用內(nèi)切酶或SWO4相比,反而降低了紙漿的強(qiáng)度和纖維素結(jié)晶度,而當(dāng)與β-葡萄糖苷酶(1.2 IU/g)或木聚糖酶(5IU/g)聯(lián)合處理時(shí),對(duì)紙漿的強(qiáng)度性質(zhì)(抗張指數(shù),撕裂指數(shù),耐破指數(shù))均有明顯改善,在溫度55 ℃C、pH 7.0條件下處理2 h,當(dāng)Y106OE-EG粗酶液用量為0.2IU/g,也β-葡萄糖苷酶1.2IU/g時(shí),與對(duì)照相比,麥草漿的抗張指數(shù)、撕裂指數(shù)、耐破指數(shù)分別提升23.68%、34.10%、20.82%。當(dāng)木聚糖酶加量為5 IU/g時(shí),與對(duì)照相比,麥草漿的抗張指數(shù)、撕裂指數(shù)、耐破指數(shù)分別提升32.65%、42.44%、25.00%。此外,木聚糖酶與SWO4或木糖苷酶的聯(lián)合處理,對(duì)麥草漿的改性也具有良好的協(xié)同作用效果。綜合而言,Y106OE-EG生產(chǎn)的內(nèi)切纖維素酶與短小芽孢桿菌生產(chǎn)的木聚糖酶Xyn30的協(xié)同處理對(duì)紙漿的改性效果最佳,為后續(xù)的共表達(dá)菌株構(gòu)建提供了理論依據(jù)。3.產(chǎn)耐堿性纖維素酶與木聚糖酶共表達(dá)菌株構(gòu)建及產(chǎn)酶條件優(yōu)化為實(shí)現(xiàn)耐堿性纖維素酶(Y106-EG)及木聚糖酶(Xyn30)在Y106-WT中的共表達(dá),采用順反子共表達(dá),融合酶表達(dá),串聯(lián)共表達(dá)三種方式,意在提高枯草芽孢桿菌Y106-WT的產(chǎn)酶能力,結(jié)果表明,以串聯(lián)共表達(dá)的方式能夠?qū)崿F(xiàn)兩酶的共表達(dá),對(duì)構(gòu)建的共表達(dá)工程菌Y106OE-EG-Xyl進(jìn)行液體發(fā)酵,發(fā)現(xiàn)該菌株在培養(yǎng)56 h后,CMCase酶活可達(dá)最高(8.20 IU/ml),木聚糖酶在菌株培養(yǎng)64 h時(shí)酶活達(dá)到最高(60.40 IU/ml),分析該菌株產(chǎn)粗酶液的酶系發(fā)現(xiàn),其濾紙酶活(0.12IU/ml),外切纖維素酶活性(0.02IU/ml),β-葡萄糖苷酶(未測(cè)到)均較低,說明對(duì)應(yīng)用于紙漿改性而言,共表達(dá)菌所產(chǎn)纖維素酶的酶系比較合理,在對(duì)紙漿進(jìn)行改性的同時(shí)不損害紙漿纖維。利用工程菌Y106OE-EG-Xyl粗酶液在最佳處理pH 7.0,最佳處理溫度55 ℃C,漿濃度10%(w/v)條件下處理麥草化學(xué)漿2 h,當(dāng)酶用量為纖維素酶0.2 IU/g木聚糖酶活1.5IU/g時(shí),與對(duì)照及單獨(dú)添加纖維素酶(0.2IU/g)及木聚糖酶(1.5 IU/g)相比,紙漿白度和強(qiáng)度性能都有改善,其中與不加酶的對(duì)照漿處理相比,紙漿白度增加2.0%ISO,抗張指數(shù)、耐破指數(shù)、撕裂指數(shù)分別增加8.7%、16.6%和9.3%,而打漿度降低了 15%。利用混料設(shè)計(jì)優(yōu)化了工程菌Y106OE-EG-Xyl發(fā)酵時(shí)培養(yǎng)基中的碳源及誘導(dǎo)劑比例,發(fā)現(xiàn)當(dāng)麩皮,玉米芯,乳糖配比為3.33%、0.83%、0.83%時(shí),液體發(fā)酵72 h,纖維素酶活可達(dá)7.9 IU/ml,木聚糖酶活可達(dá)74.5 IU/ml,木聚糖酶活比優(yōu)化前提升了 14.1個(gè)酶活單位,且木聚糖酶與內(nèi)切纖維素酶的比由原來的7.5提升至 9.4。4.紙漿的酶法改性機(jī)制研究通過對(duì)Y106OE-EG粗酶液處理前后纖維質(zhì)量變化,纖維結(jié)晶度(XRD)及紅外光譜(FITR-ATR)等的變化分析發(fā)現(xiàn),經(jīng)重組菌Y106OE-EG粗酶液處理后,楊木CMP和麥草CP的纖維質(zhì)量得到明顯改善,且改善效果好于松木CMP。Y106OE-EG粗酶液處理后,楊木CMP及麥草化學(xué)漿的結(jié)晶度與對(duì)照相比明顯提高,但松木CMP結(jié)晶度則提高不明顯,三種漿經(jīng)酶處理后紙漿中的氫鍵強(qiáng)度均有所提升。分別提取了麥草CP、松木CMP和楊木CMP中的木質(zhì)素組分,研究了木質(zhì)素對(duì)Y106OE-EG的酶蛋白吸附特征,發(fā)現(xiàn)松木CMP和楊木CMP的木質(zhì)素對(duì)纖維素酶蛋白的吸附能力明顯高于麥草漿中的木質(zhì)素,木質(zhì)素對(duì)蛋白的不可逆吸附將影響酶對(duì)纖維底物的作用,因此相對(duì)而言,Y106OE-EG酶液更適合用于麥草漿的改性。分別利用Y106OE-EG和Y106OE-Xyl及共表達(dá)菌株Y106OE-EG-Xyl的粗酶液(EG 0.2 IU/g、Xylanase 1.5 IU/g、EG 0.2 IU/g-Xylanase 1.5 IU/g)處理紙漿,發(fā)現(xiàn)與對(duì)照或只添加EG或木聚糖酶的樣品相比,共表達(dá)菌株的粗酶液處理后紙漿纖維的平均長(zhǎng)度增加,寬度幾乎不變,長(zhǎng)寬比變大,細(xì)小纖維含量減少,卷曲指數(shù)及扭結(jié)指數(shù)均有所降低,且共表達(dá)菌株的粗酶液處理效果優(yōu)于單獨(dú)酶的處理效果。利用紅外譜圖對(duì)共表達(dá)菌株Y106OE-EG-Xyl粗酶液處理前后草漿的吸收峰相對(duì)強(qiáng)度進(jìn)行分析,發(fā)現(xiàn)經(jīng)共表達(dá)菌株粗酶液處理后,氫鍵強(qiáng)度明顯提升。利用SEM觀察了重組菌Y106OE-EG及共表達(dá)菌株Y106OE-EG-Xyl的粗酶液處理前后草漿纖維表面形態(tài)變化,發(fā)現(xiàn)經(jīng)兩菌株的粗酶液處理后,與對(duì)照相比,紙漿中的細(xì)小纖維含量明顯減少,纖維變得平整。酶處理后紙漿在纖維質(zhì)量、纖維素結(jié)晶度、氫鍵強(qiáng)度、表面形態(tài)等方面發(fā)生的上述變化,是酶處理改善紙漿強(qiáng)度和濾水性能的內(nèi)在原因。分別從酶的結(jié)構(gòu)和性質(zhì)、蛋白表面電荷、蛋白的疏水性、蛋白在紙漿纖維上的吸附等角度,探討了 Y106-EG所產(chǎn)粗酶液與來源于特異腐質(zhì)霉的三個(gè)耐堿性內(nèi)切纖維素酶H.EGⅠ、H.EGⅡ和H.EGⅤ以及來源于其它芽孢桿菌的兩個(gè)耐堿性內(nèi)切纖維素酶z-16-EG和A30-EG對(duì)麥草漿的改性差異及內(nèi)在原因。研究發(fā)現(xiàn),與其它五種耐堿性內(nèi)切纖維素酶相比,Y106-EG由于酶蛋白對(duì)底物的親和力相對(duì)較大,且在pH 7.0時(shí),pH值低于其自身等電點(diǎn)使其氨基酸易被帶上正電荷,另外,蛋白表面的Zeta電位與其它幾種耐堿性內(nèi)切酶相比負(fù)值較小,且蛋白的疏水性小,這些都使得Y106-EG酶蛋白更易于與帶負(fù)電荷的細(xì)小纖維發(fā)生親水性結(jié)合,從而有利于酶降解細(xì)小纖維。此外,Y106-EG酶蛋白是典型的(β/α)8桶狀結(jié)構(gòu)特征,結(jié)構(gòu)穩(wěn)定性較好且開口寬闊的活性中心使其可以容納更多類型不同的多糖支鏈,在催化降解復(fù)雜底物時(shí)有較大優(yōu)勢(shì),該酶的CBM屬于A型CBM,易于結(jié)合于結(jié)晶型纖維素多糖上。這些特征使得Y106-EG在用于紙漿改性時(shí)表現(xiàn)出較好的優(yōu)勢(shì)。
[Abstract]:The straw etc. pulp drainability are poor, low intensity, so its application is limited, need to be modified to improve the drainage and strength properties of the general production process. Compared with chemical modification, cellulase (mainly enzyme EG) treatment on pulp modification is an environmental friendly the technology, and has been shown to improve pulp drainability, has good effect to improve paper strength and so on. Because of the pulping and papermaking process often in alkaline conditions, this requires the use of enzymes to maintain the enzyme activity in the condition of high pH, effectively guaranteeing the catalytic effect. But already on the market the goods are mostly acidic cellulase enzyme, in alkaline conditions, enzyme activity is very low. Although the domestic and foreign research on alkaline cellulase is deepening, but there are still many problems, for example, has a strain producing alkaline cellulase yield Low enzyme system is not reasonable, enzyme modification mechanism has not been fully understood. Therefore, to improve the yield of alkaline cellulase, optimizing cellulase enzyme system, to reduce production cost and improve the effect of modification of pulp, and studies on enzymatic modification mechanism, to promote the application of enzyme in papermaking industry, has important to reduce the production cost. Based on the above background, this paper based on the previous research in the laboratory, through the construction of alkaline cellulase strains, in the hope of improving yield of cellulase; at the same time through the construction of alkaline cellulase and xylanase co expression strain, to achieve the optimization of modified enzyme system, improve the effect of modified enzyme method; at the same time from different angles on the pulp enzymatic modification mechanism. The main research contents and results are as follows: 1. the expression of cellulase and alkali resistance of pulp modification effect for research For the pulp for modification of alkaline cellulase in the laboratory, based on the previous research of amplification from humicola insolens three alkaline endoglucanase H.EG I and H.EG II, H.EG V gene and heterologous expression in Pichia pastoris GS115; at the same time, the success of three endoglucanase Y106-EG heterologous expression. Different from Bacillus subtilis in Escherichia coli BL21, properties of z-16-EG and A30-EG. determination of purified recombinant alkaline cellulase, found that the optimum pH is about 6.5-7.5 in the six kinds of endoglucanase optimum temperature between 50, -60 DEG C, the enzyme 1h in pH placed under the condition of 6.0-8.0 can maintain more than 60% of the enzyme activity among them, Y106-EG, z-16-EG and H.EGV under the condition of pH 9 for 1 h can maintain more than 60% enzymes. Six kinds of alkali resistance enzymes used in wheat straw modified, Y106-EG found in the amount of enzyme is only 0.2 IU/g Under the condition, compared with the control, can reduce 12.5% of the beating degree, tensile index, burst index and tear index were increased by 14.6%, significantly higher than the other five kinds of alkaline endoglucanase 14.3% and 10.7%. of the pulp, showing good potential application prospect in recombinant.2. enzyme on Y106OE-EG optimization of enzyme treatment of different pulp modification and other enzymes to improve the synergistic effect of alkali cellulase Y106-EG production by genetic engineering method, the homology of Y106-eg gene overexpression, by fermentation laboratory optimization of fermentation medium, the enzyme activity reached 8.45 IU/ml CMCase fermentation liquor, is 8.28 times the starting strain. The engineering strain Y106OE-EG crude enzyme of poplar CMP (Yang Mu chemical mechanical pulp), CMP pine (pine chemical mechanical pulp (CP) of wheat straw, wheat straw chemical pulp) was modified to study found that modification effect The fruit followed by wheat straw CP poplar CMP pine CMP. on enzymatic modification of enzyme treatment conditions (temperature, time and pH) were optimized, when the enzyme dosage is 0.2 IU/g pulp, pH 7, temperature 55 degrees under the condition of wheat straw treatment for 2 h, compared with the control without enzyme the pulp tensile index, burst index and tear index were increased by 15.4%, 16.9% and 11.8%. to study the effect of modified engineering strain Y106OE-EG crude enzyme solution with other enzymes, it is found that the combined treatment with endo cellulase cellulose Y106OE-EG expansion factor SWO4, compared with the single use enzyme or SWO4, but reduce the strength and crystallinity of cellulose pulp, while beta glucosidase and glucose oxidase (1.2 IU/g) or xylanase (5IU/g) combined treatment, the strength properties of the pulp (tensile index, tear index, burst index) were significantly improved, at a temperature of 55 DEG C, pH 7 Under 2 h, when the Y106OE-EG crude enzyme dosage is 0.2IU/g, or beta glucosidase 1.2IU/g when compared with the control, the tensile index, tear index of wheat straw pulp, bursting index were increased by 23.68%, 34.10%, 20.82%. when xylanase dosage was 5 IU/g, compared with the control, anti the tensile index, tear index of wheat straw pulp, bursting index were increased by 32.65%, 42.44%, 25.00%. in the combined treatment of xylanase and xylosidase or SWO4, modification of wheat straw has good synergistic effect. In general, the production of Y106OE-EG fiber endo cellulase and Bacillus pumilus production xylanase Xyn30 co processing is the best modifier of pulp for strain construction provides a theoretical basis for.3. producing alkaline cellulase and xylanase expression strain construction and optimization of fermentation conditions for alkaline cellulase co expression of follow-up (Y106- EG) and xylanase (Xyn30) were expressed in Y106-WT, the cistron expression, fusion enzyme expression, series co expression in three ways, in order to improve the enzyme producing ability of Bacillus subtilis Y106-WT results show that co expression in series co expression way to achieve the two enzyme, liquid fermentation on the establishment of co expression engineering bacteria Y106OE-EG-Xyl, found that the strain in the culture after 56 h, CMCase activity was the highest (8.20 IU/ml), xylanase strain was cultured in enzyme activity reached the maximum of 64 H (60.40 IU/ml), found that the enzyme production of the strain analysis of crude enzyme, the filter paper activity (0.12IU/ml), cellobiohydrolase activity (0.02IU/ml), beta glucosidase (not detected) were low, indicating the corresponding modification for pulp, co expression of enzymes of bacteria producing cellulase is reasonable, in the pulp modified with no damage to the pulp fiber. By using engineering bacteria Y106 OE-EG-Xyl crude enzyme solution in the optimal treatment of pH 7, the optimum processing temperature is 55 DEG C, plasma concentration of 10% (w/v) under the condition of wheat straw chemical pulp processing 2 h, when the dosage of enzyme was 0.2 IU/g cellulase and xylanase activity of 1.5IU/g, and the control and the addition of cellulase and xylanase (0.2IU/g) (1.5 IU/g) compared have, improve pulp brightness and strength properties of the pulp, compared with the control treatment without enzyme, the whiteness of pulp increased 2.0%ISO, tensile index, burst index and tear index were increased by 8.7%, 16.6% and 9.3%, and the beating degree is reduced by using 15%. mixture design optimization of engineering bacteria Y106OE-EG-Xyl fermentation the medium carbon source and inducer ratio, when the wheat bran, corn cob, lactose ratio was 3.33%, 0.83%, 0.83%, 72 h liquid fermentation, cellulase activity was 7.9 IU/ml, the xylanase activity was up to 74.5 IU/ml, the activity of xylanase than before optimization improved 14.1 enzyme activity Unit, and xylanase and CMCase by enzyme method than the original 7.5 to 9.4.4. pulp modification mechanism through the study on the change of fiber quality of Y106OE-EG before and after enzyme treatment, the crystallinity of the fiber (XRD) and infrared spectroscopy (FITR-ATR) and other changes after analysis found that recombinant Y106OE-EG enzyme treatment after the fiber quality of poplar CMP and wheat straw CP was obviously improved, and the improvement effect is better than the pine CMP.Y106OE-EG crude enzyme solution after crystallization of poplar CMP and wheat straw pulp were significantly increased compared with the degree of crystallinity of CMP, but the pine increase is not obvious, three kinds of pulp by hydrogen bond strength were enzyme treatment after the upgrade. In the pulp were extracted from wheat straw CP, CMP and CMP in pine poplar lignin fractions, of lignin on Y106OE-EG enzyme protein adsorption characteristics, found that pine CMP and poplar CMP lignin on cellulase protein The adsorption capacity was significantly higher than that of wheat straw pulp lignin, lignin on protein irreversible adsorption will affect the effect of enzyme on fiber substrates, so relatively speaking, Y106OE-EG is more suitable for wheat straw pulp enzyme modification. Y106OE-EG enzyme and Y106OE-Xyl and co expression strain Y106OE-EG-Xyl (EG 0.2 IU/g, respectively, by Xylanase 1.5 IU/g, EG 0.2 IU/g-Xylanase 1.5 IU/g) treatment of pulp, we found that compared with the control or only adding EG or xylanase samples, the average length of total crude enzyme strains after the expression of pulp fibers increased, the width is almost unchanged, the ratio of length to width becomes larger, reduce the fines content, curl index and kink index decreased, and co expression of treatment effect of crude enzyme treatment effect is better than that of the strains. The infrared spectra of co expression strain Y106OE-EG-Xyl crude enzyme solution before and after the treatment of straw pulp and the absorption peak is relatively strong The degree of analysis, found by co expression strain of crude enzyme treatment, hydrogen bond strength significantly improved. Using SEM surface morphology changes were observed before and after the straw fiber and co expression of recombinant Y106OE-EG strain Y106OE-EG-Xyl crude enzyme treatment, found that the crude enzyme treatment of strain two, compared with the control, the content of fine fiber pulp the fiber becomes smooth. Significantly reduced after enzyme treatment in pulp fiber quality, cellulose crystallinity, hydrogen bond strength, the change of surface morphology occurred, is the inherent reason of enzyme treatment improve the pulp strength and drainage performance. From the structure and properties of the enzyme, protein surface charge, hydrophobic protein, protein in the pulp fiber adsorption angle, discusses the Y106-EG production and the crude enzyme from humicola insolens three alkaline endoglucanase H.EG 1, H.EG 2 and H.EG V and from the other The two Bacillus alkaline endoglucanase z-16-EG and A30-EG on wheat straw pulp modified difference and internal reasons. The study found that, compared with other five kinds of alkaline endoglucanase, Y106-EG as affinity enzyme protein of substrate is relatively large, and in pH 7, pH value is lower than the isoelectric point of the amino acid easy to be with a positive charge, in addition, Zeta protein negative surface potential is lower compared with other several alkali resistant enzymes, and protein hydrophobicity, which makes Y106-EG protein more easily and negatively charged fine fiber hydrophilic combination, which is beneficial to the enzymatic degradation of fine fiber. In addition, Y106-EG protein is a typical (alpha / beta) 8 barrel structure characteristics, good structure stability and wide opening activity center which can accommodate more different types of branched polysaccharides, in catalytic degradation of complex substrate is bigger The advantage of this enzyme, CBM belongs to A CBM, easy binding to crystalline cellulose polysaccharides. These characteristics make Y106-EG used in pulp modification showed better advantage.

【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TS727;Q55

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