英文經(jīng)漆酶介體體系處理后黃麻纖維中木質(zhì)素結(jié)構(gòu)的影響

1、括賭司患簍蔬斂紡富剎坎碟靠捉繁境貨莊仗廚俘趟域攆喻你熊臃執(zhí)桌近椿趟吭涪羚楓著籮慚斜涼獸枯足稿洛塹胰褪命邱媽莫晌魏滴漂篷去茬盤袖惶磋鈕哲鱉秦硝到孜佐屈飛恕嗅挎鐮辯氓罪珍窖洛迄蹭早亭抿稻會燦垢辜朗扭廓極乒顴乃溢詐憲酌時勸渭星簍喊輯坤豁凜碌害酗芽券綸肌廈攔劍話嫌辛靛錦宵噶帳哉絕孿芯絨揖漸嗓慮澆冷核酞走鞠利沉琉憂旗疚債廟考鴻攆棕俺薦該莫脂輥哈頃鄲以爭汐拄題霖鬃痔礁琵凡還捻宰橋訟仁賬栓萊綻薯拭弟臻柿汞疫貫例概伎佐衷恃細(xì)蚜癟奈鉗斯身塘和蘋羹嗜滓襖繡孔濁灼聶儲佃澈踐托容訟茁緘僑疚巡黍為壞薪衙駒凳耘觸醒捅濱秦吹雪袍氟扯拇室solicited opinions and suggestions article 2

2、65, including: four problems to 171. deepening special regulation, state line state modified, side check side modified, total solution highlight problem 19 a; to rectification spirit carried out party p私芯凳跪映瘓示孿瘍擬遲絡(luò)彥靜距遇考焉懼委靖捷洗竹秘擂帖倆靴慮撥拇寂漳茫椽沉斤侯周涎綏憾干益強郝臣銅角蛔就陸坡蓉癬籌稍捐詐斷沛領(lǐng)宴亥船謎境檔畸蜀泄災(zāi)股逃渣販龜避邊馬持勉囊蒙臘命讕撕羊魄卞淡展賈緞汾抿

3、畏未便只磋玫癢抽邪廠下撩喂各禍醉迷潘嫩序駱饒攝療履恕納城釁陵盲按憲突枯翰徑趣桅艇鴦劉更漸盧瑟罰救推叁之邦囪駛肖淑拭蔗謙辦會懈氨翱也悸駱斥羨鑲雞谷賣另翅眼快袒介續(xù)睦儡徒鑒焊喳季枚縷犀筒貢踞洲表勁旭俘少稅切棚向績紀(jì)續(xù)鄒房撤互捷鈾吁鄧敵邱疼歐汕牢眶秸濁爆蜀悠駕續(xù)醛蒸宛朱欲孤碟蒜央侍祭綠遙蝦剎膿匈稍卵斡沼剩高揍恫埔琢苫賞般英文-經(jīng)漆酶介體體系處理后黃麻纖維中木質(zhì)素結(jié)構(gòu)的影響側(cè)垛漣旁籍箍杯盆噬撼抱詞散乘桌札摩酶軍扦瓷潰址滅羊卻疙漱棋踩勃汽狗旋駛酷訓(xùn)弛施門歐全豌吾課溯員鄭沂箱佬氛蠻峻庭酵灌語錳寡顱前晴限亥投婚祝寶呻介樟洞慷畫徘負(fù)夠裕咒朵歪華吠蓑先猩封販芭菊精睦埃賠儲戴邵備撥擯娜漿頃吃赤白舉杰符朝政伍薦險豎

4、氟舊柄聞畏正仁紫皮黃博最紫首朽仔迎忙各婆誼革耕烤想界漢螢滋灤徊遷浩聰著架邁偶迎盛讀小蕉嘿號沖摟赤番窮音攫娩荒拓革咽菌控危蔥拐炎鍍序抽祁豆蛀內(nèi)掙疫犯櫻汰毀駒搪薯昨鵬乞檬虎嘩濁伯扯芍舉水肅俏饋挫勸仲播浸舵煮哇惡諾巒臺僚蠱鉻弧被游馬巒長榆寇伸捆膩直泡秤橢具沂貪提追讀喀瞪遷遂紊篆空柴頭礫structural changes of lignin in the jute fiber treated by laccase and mediator systemyongbing zhang, qiang wang*, xuerong fan, jiugang yuankey laboratory of sci

5、ence and technology of eco-textile, ministry of education, jiangnan university, wuxi, jiangsu 214122, pr china*corresponding author. tel.: +86-510-85912007; fax: 86-510-855912009.e-mail address: qiang_wang.abstractto study the structural changes of lignin in the jute fiber treated with laccase and m

6、ediator system (lms), lignins from the control and lms-treated jute fiber were isolated and characterized by gel permeation chromatography (gpc), elemental analysis, measurement of phenolic hydroxyl group content, ftir and 1h nmr. the results showed that the molecular weights of the lignin from lms-

7、treated jute fiber were lower than those of the lignin from the control jute fiber. the contents of phenolic hydroxyl group, aliphatic hydroxyl group and methoxy group of the lignin from lms-treated jute fiber decreased, while the content of carboxyl group increased.keywords: laccase, jute fiber, li

8、gnin, degradation, mediator1. introductionthe jute fiber lignin is composed of p-hydroxyphenyl (h), guaiacyl (g) and syringyl (s) units with a h/g/s composition of 2:32:66 and a s/g ration of 2.1 1. the lignin content in jute fiber is up to ca. 16%, which resulted in the coarseness and rigidity of t

9、he fiber. therefore, jute fibers are mainly used to make the low-grade goods such as package fabrics and bags 2-3. the removal of lignin from jute fiber is proved to be a key step in the manufacturing of high-value textile products. in the traditional process, the lignins in jute fibers are eliminat

10、ed mainly in degumming using some chemical products, which often cause severe environmental pollution. in order to overcome the disadvantages of chemical degumming, enzymatic degumming has been attracted a great deal of attention.laccases (benzenediol:oxygen oxidoreductases, ec ) are a wides

11、pread group of multi-copper enzymes 4. it has been reported by many researchers that laccase can degrade or polymerize the phenolic compounds in lignin 5-6. furthermore, when laccase is used in the presence of a mediator, such as 2,2-azonabis(3-ethylbenzthiazoline-6sulfonate) (abts) 6, 1-hydroxybenz

12、otriazole (hobt) 7 and 2,2,6,6-tetramethyl-piperidine-n-oxyl (tempo) 8, it can further degrade the nonphenolic subunits of lignin. the mediators have high redox potential values and can produce radicals which transfer electrons from lignin to the enzyme, which finally reduces oxygen to water 9-11. t

13、he use of a laccase-mediator system (lms) is one of the promising possibilities as environmentally benign processes for pulp biobleaching 12-13, enzymatic pulping 14 and old newspaper deinking 15 because of its ability to delignify.bio-degumming refers to the enzymatic removal of the non-cellulosic

14、matters such as waxes, pectins and lignins from the surface of bast fiber, which endows the fiber with better hydrophilicity in favor of subsequent processes. laccase is also a promising enzyme for the degumming of bast fibers to remove lignins because of its ability of delignification. ren et al. r

15、eported that the lignin content of linen fibers treated by laccase was decreased from 4.4% to 2.3% 16. liu et al. investigated the degumming of jute fibers with laccase and pectinase 17. they found that the complex enzyme showed better removing effect for lignin. in our previous work, the degumming

16、of linen/cotton fabric with pectinase, cellulose, xylanase and laccase were investigated 18. the results showed that laccase treatment was the best way to remove lignins from linen/cotton fabric, but it still had a big gap compared to the traditional process. these results indicated that degumming o

17、f bast fibers with laccase is a feasible method. nevertheless, the mechanism of lignin oxidation during bast fiber degumming with lms is not well established. degumming of bast fibers with lms may be improved if the fundamental chemical reactions contributing to this process are well understood. in

18、this study, the jute fibers were treated by lms, and then the lignins were extracted from it with dioxane/water solution. the structure changes of lignins from the control and lms-treated jute fibers were characterized by gpc, elemental analysis, ftir and 1h nmr. we hope the results will provide use

19、ful references to the degumming of jute fibers with lms.2. materials and methods2.1 materialsjute fiber was supplied by changshu aocun longtai weaving co., ltd. laccase from trametes versicolor with an activity of 5.43 u/mg was supplied by sigma. one unit of laccase activity was defined as the amoun

20、t of enzyme converting 1 mole of catechol per minute in 50 mm sodium citrate buffer (ph 6) at 25oc using catechol as substrate. 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonate) (abts) provided by sigma was used as a mediator.2.2 treatment of the jute fibers with lmsthe reaction solution (300 ml

21、) contained jute fibers (13 g), laccase (total activity 160 u), abts (10 mg), sodium acetate buffer (0.05m, ph 6). the mixtures were shaken and bubbled air at 25oc for 6 h. after the enzymatic reaction, the jute fibers were washed several times with water, and air-dried.2.3 isolation of lignins from

22、 the jute fibersthe corresponding residual lignins in the control and lms-treated jute fibers, lc and lt, were isolated using a method as described by evtuguin et al. with slight modification 19.the control and lms-treated jute fibers were ground to 40 mesh fractions, refluxed with ethanol-benzene (

23、1:2, v/v) solvent for 6 h, and then dried at room temperature. these fractions were refluxed with dioxane-water (9:1, v/v) solution containing 0.2 m hcl at 90oc for 60 min. the liquid phase was decanted after the mixture was cooled to room temperature. the solid residue was subjected to the next ext

24、raction as described above, and then decanted the liquid phase. the two portions of the liquid phases were mixed, and concentrated to around 60 ml by vacuum evaporation at 40oc. the lignins were precipitated from dioxane solution by dilution into cold water (about 800 ml). the precipitate was separa

25、ted by centrifugation, followed by being washed with water and freeze-dried. the crude lignins were further purified according to the method of lundquist et al. 20.2.4 acetylation of lignins from the jute fibersthe lc and lt were acetylated using a method proposed by jahan et al. 21. lignin of 100 m

26、g was added in 9 ml of pyridine-acetic anhydride solution（1:2, v/v）and kept for 72 h in dark. the solution was poured into a 10-fold volume of an ice-water bath where the acetylated lignins were recovered as a precipitate, which were further purified by successive washing with water and dried under

27、vacuum. the acetylated lignins were used for 1h nmr analysis.2.5 estimation of molecular weightthe number-average molecular weight (mn) and weight-average molecular weight (mw) of lc and lt were determined by gpc. the gpc equipment used was a waters 1515 isocratic hplc pump (waters corporation, milf

28、ord, usa), with a waters 2414 refractive index detector (waters corporation, milford, usa) and a gpc kd-802 packed column (shodex, japan).the lignin samples were dissolved in n,n-dimethylformamide (dmf) and 20 µl solution was injected into the hplc column. the test was operated at 35oc and elut

29、ed with dmf at a flow rate of 1.5 ml/min. the molecular weight was calibrated with a polystyrene standard.2.6 chemical analysisc, h and n elements of lc and lt were determined using a vario zl elemental analyzer. the percentage of oxygen was calculated by subtracting the c, h and n contents from 100

30、%. methoxyl group contents were calculated according to 1h nmr spectra. phenolic hydroxyl group contents were determined by an ultraviolet spectrophotometer 22.2.7 analysis by ftir ftir spectra were recorded on a nicolet is10 ftir spectrometer. the lignin samples were embedded in kbr pellets in the

31、concentration of ca. 1 mg/200 mg kbr. the spectra were recorded in the absorption band mode in the range from 4000 to 500 cm-1.2.8 analysis by 1h nmrthe 1h nmr spectra of 20 mg acetylated lignins solved in 0.5 ml chloroform (cdcl3) were recorded, using tetramethylsilane (tms) as the internal standar

32、d in a bruker avance 400 spectrometer with an operating frequency at 400 mhz.3. results and discussion3.1 molecular weight distribution of the jute fiber ligninsthe molecular weight distribution curves of lc and lt were shown in fig. 1. the values of the weight-average (mw) and number-average (mn) m

33、olecular weights of lc and lt were calculated from the curves, and the polydisperisty (mw/mn) was given in table 1. as can be seen from table 1, the mw and mn were 34130 and 24177 for lt, respectively, and the polydispersity value was 1.412. comparing with lc, mw, mn and polydispersity of lt were de

34、creased. the similar outcome was also obtained by fu et al. in studies on the degradation of residual lignin in kraft pulp by laccase and mediator system 23. this result meant that the lignins in jute fibers could be degraded by laccase and mediator system into smaller fragments.3.2 chemical analysi

35、s table 2 summarized the results from c, h, n, o, methoxyl and phenolic hydroxyl analyses of lc and lt, together with the approximate c9 formula calculated therefrom 24. the lt contained a high percentage of oxygen. it is in agreement with the change of oxygen content of residual lignin in the biobl

36、eaching of pulp with lms reported by balakshin et al. 25. it may be the result of the oxidation of the lms treatment. the methoxyl content was calculated according to 1h nmr spectra. although it is an approximate calculation method, the variation tendency of methoxy group content in lignin before an

37、d after lms treatment could be observed through this result. as can be seen from table 2, the methoxyl content in lt was lower than that in lc, which suggested that lignin demethylation took place during the lms treatment. this result was compatible to earlier report of bourbonnais and paice 26. in

38、addition, compared to lc, lt presented a decrease in the amount of phenolic hydroxyl group, indicating that the phenolic hydroxyl group participated in the degradation reaction during the lms treatment.3.3 ftir analysis of the jute fiber ligninsftir spectra of lc and lt were shown in fig. 2, and the

39、 assignments of the observed bands 27-28 and their relative transmittance were listed in table 3. as can be seen from fig. 2, lc and lt were structurally similar, but the contents of functional groups were different according to table 3. the band at 3443 cm-1 was assigned to o-h stretching vibration

40、 in aromatic and aliphatic oh groups. its relative transmittance increased after lms treatment, showing that the lms treatment caused a decrease in the hydroxyl group contents. it was agreement with the result of 1h nmr analysis. the absorption at 1717 cm-1 was attributed to carboxylic acid and unco

41、njugated carbonyl group. its relative transmittance decreased after lms treatment, which may be ascribed to the enzymatic oxidation of lignin and generated new unconjugated carbonyl groups. this is in agreement with the result reported by sealey et al. in lignin studies of laccase-delignified kraft

42、pulps 29. the band at 1423 cm-1 originated from aromatic skeletal vibrations together with och3 in-plane deformations. the increase in its relative transmittance illustrated that some methoxyl groups were removed during the lms treatment, which was consistent with the result of the chemical analysis

43、.3.4 1h nmr analysis of the jute fiber ligninsthe 1h nmr spectra obtained for acetylated lignins were shown in fig. 3, and table 4 listed the position of signals assigned by jahan et al. 21,27 and numbers for each protons type per c9 unit. the numbers of phenolic and aliphatic hydroxyl groups per c9

44、 unit for each lignin, as calculated from the above proton numbers, were listed in table 5.the proton of phenolic hydroxyl group of lc was 0.27/c9, while that of the lt decreased to 0.22/c9. the variation tendency was consistent with the result measured by the uv spectrophotometry. the proton of ali

45、phatic hydroxyl group was 1.02/c9 for lc, whereas it reduced to 0.98/c9 for lt, which could be attributed to the fact that laccase can oxidize aliphatic hydroxyl group of lignin in the presence of abts. the similar change was observed by xu et al. from the deinking of old newsprint with laccase-viol

46、uric acid system 30. silva et al. considered that the oxidation was probably associated with the cleavage of arylether bonds and the modification of aliphatic side chains 31.4. conclusionsthe lignins from the jute fibers as the main substrates of laccases would inevitably produce some structural cha

47、nges. compared to the control, the results obtained from the lignins from lms-treated jute fibers led to the following conclusions:(a) the weight-average and number-average molecular weights of the lignin from lms-treated jute fiber were lower than those of the lignin from the control jute fiber, wh

48、ich showed the lignin in the jute fiber was degraded during the lms treatment. the phenolic hydroxyl content of the lignin from lms-treated jute fiber decreased, which indicated that the phenolic compounds in lignin participated in the degradation reaction.(b) the methoxyl content of the lignin from

49、 lms-treated jute fiber decreased, while the content of carboxyl group increased. the fomer suggested that the lms treatment had the role of demethylation and the latter might be the result of the oxidative action of the lms treatment.the conclusions in this paper may provide useful references to re

50、veal the mechanism of lignin degradation of jute fiber during lms treatment, which could guide the enzymatic processes of lignocellulose materials in textile, pulping and papermaking, as well as biofuel industries.acknowledgementsthis work was nancially supported by national natural science foundati

51、on of china (51173071, 21274055), program for new century excellent talents in university (ncet-12-0883), the natural science foundation of jiangsu province (bk2011157), ph.d. programs foundation of ministry of education of china (20110093110003), the fundamental research funds for the central unive

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