【作者】 袁丽；

【导师】 陈振华； 刘选明；

【作者基本信息】 湖南大学 ， 材料科学与工程， 2013， 博士

【摘要】 随着世界经济的高速发展，工业上对化石燃料日益增加的依赖性与有限的化石资源的矛盾严重影响了国家的能源安全。利用生物质转化得到生物燃料可以降低国家对原油进口的依赖性，增强国家安全。在我国利用木质纤维素原料来生产生物乙醇具有重要的经济效益和社会意义。我国木质纤维素资源丰富，但是利用率非常低，大部分只是作为燃料或造纸工业等使用，不仅浪费资源并且严重污染环境。因此，在我国开发利用木质纤维素原料来生产燃料乙醇前景广阔，具有重要的现实意义。本论文选择小麦秸秆和桦木木屑作为草本类和木本类这两种植物类型的代表原料，在湿法球磨中采用稀柠檬酸、简青霉H5和超声波的处理方法，来降解小麦秸秆和桦木木屑。研究常温常压条件下，将球磨方法与稀酸处理法、真菌处理法和超声处理法联用，来降解木质纤维素的过程。论文首先采用湿法球磨联合柠檬酸对秸秆和木屑进行降解，研究不同pH值的柠檬酸对秸秆和木屑酸水解的作用，得到如下研究结果：（1）稀酸-球磨系统可以在常温常压下降解秸秆和木屑，还原性糖产率分别为186.9mg/g和120.5mg/g。（2）商品纤维素酶的加入不能与机械球磨-稀酸降解法形成良好的协同作用，糖产率低于单独的机械球磨-稀酸降解法，酶活力也快速丧失。（3）稀酸-球磨降解过程对葡萄糖和木糖起不同的作用，其中葡萄糖的含量随着球磨时间的延长而增加，木糖的含量随着球磨时间的延长而减少。球磨体系的pH值会影响木屑的降解情况，木屑在pH=5、6的柠檬酸体系中得到的糖产率高于pH=3、4的体系中的糖产率。（4）随着球磨时间的延长，反应液的pH值向碱性方向偏移，在球磨24h后达到平衡，秸秆和木屑的最佳降解体系的pH值分别为6.5和8.5。（5）XRD和ESEM测试结果表明，球磨破坏了纤维素的晶体结构，增大了无定形态纤维素的比率和反应活性面积，从而使得秸秆和木屑中的纤维素更容易被弱酸渗透，从而发生水解。（6）红外光谱和紫外扫描结果表明，球磨处理之后秸秆和木屑中的木质素成分基本被破坏，木质素的降解使得纤维素更容易被水解，从而提高其糖化率。与工业上常用的高温高压酸水解法相比，机械球磨协同稀酸的方法能够在常温常压下降解天然木质纤维素，反应简单温和，基本无污染，但是糖化率仍然较低。其次采用湿法球磨联合稀柠檬酸和简青霉H5对秸秆和木屑进行降解，研究简青霉H5对秸秆和木屑酸水解及生物降解的作用。得到如下实验结果：（1）简青霉的加入可以显著的促进秸秆和木屑的降解，还原性糖产率分别为216.9mg/g和245.3mg/g。（2）简青霉的加入可以与稀酸-球磨降解法形成良好的协同作用，简青霉H5的生长及其产酶活力可以在球磨条件下保持24h，糖产率也高于稀酸-球磨降解法，简青霉H5非常适合球磨降解天然木质纤维素产物。（3）稀酸-真菌-球磨过程也对葡萄糖和木糖起相反的作用。简青霉H5的加入会影响木屑的降解效果。其中木屑在pH=4、5的H5-柠檬酸体系中得到的糖产率高于pH=3、6的H5-柠檬酸体系中的糖产率。（4）加入简青霉H5以后，随着球磨时间的延长秸秆和木屑反应液的pH值向碱性方向偏移，在球磨12h后基本达到平衡，最佳降解体系的pH值分别为6.5和7.5，基本保持在中性范围。（5）XRD和ESEM图结果表明，稀酸-真菌-球磨系统破坏了秸秆和木屑的晶体结构。在球磨短时间内，简青霉H5加入后由于优先分解无定型纤维素部分，秸秆和木屑的结晶度会高于不加入简青霉H5的。长时间球磨之后秸秆和木屑的结晶度都会下降，无定形态纤维素的比率和反应活性面积增大，从而使得秸秆和木屑中的纤维素更容易被弱酸渗透，更容易被水解。（6）红外光谱和紫外扫描结果表明，球磨处理之后秸秆和木屑中的木质素成分基本被破坏，简青霉H5的加入促进了木质素部分的降解，从而提高糖化率。总之简青霉H5的加入可以显著促进秸秆和木屑中纤维素和木质素的降解，糖化率较高，反应条件温和，反应过程简单且基本无污染，易于工业化生产。最后采用超声波技术对桦木木屑进行预处理，之后再进行固液球磨降解，发现短时间的超声预处理可以促进木屑的水解。得到如下实验结果：（1）超声预处理10min能有效促进木屑水解，还原性糖产率为126.84mg/g木屑。（2）超声波预处理可以显著促进木屑在稀酸-真菌-球磨系统中的降解情况，提高了木屑的糖化率。木屑中的还原糖得率高峰的时间从48h缩短为36h，最大还原糖得率从245.3mg/g木屑增大为311.2mg/g木屑。（3）超声波预处理对葡萄糖和木糖的溶出都起到促进作用。（4）超声波预处理后，。随着球磨时间的延长木屑降解后反应液的pH值向碱性方向偏移，在球磨12h后基本达到平衡，球磨后反应液基本保持在中性。（5）XRD和ESEM图结果表明，超声波预处理使得木屑的结晶度略有下降，而稀酸-真菌-球磨系统破坏了木屑的晶体结构。短时间（12h）球磨处理纤维时，超声波预处理过的木屑纤维的结晶度比不经过超声波处理的要高。随着球磨时间的延长，木屑纤维素晶体被大量破坏，生成更多的不定形态纤维素，结晶度下降，反应活性面积增大，从而使得木屑中的纤维素更容易被弱酸渗透，更容易被水解。（6）红外光谱和紫外扫描结果表明，球磨处理之后秸秆和木屑中的木质素成分基本被破坏，而超声波预处理过程促进了木屑中木质素部分的降解，使得纤维素更容易被水解，从而提高其糖化率。因此超声波预处理的加入可以显著促进木屑中纤维素和木质素的降解，并且对木屑中葡萄糖和木糖的溶出都起到促进作用，糖化率较高，反应条件温和，反应过程简单且基本无污染，易于工业化生产。本论文采用的固液球磨联合稀酸、真菌、超声波作用的方法降解天然木质纤维素原料小麦秸秆和木屑。降解后的糖化率较高，反应过程简单，反应条件温和，对环境基本无污染，微生物成本低，易于工业化应用，为生物质转化乙醇提供了一条清洁、有效的新途径。更多还原

【Abstract】 The conflicts between the increasing dependence on fossil fue ls in the industryand the limitio n of fossil resource impact serious ly on the country’s energy security.Converting bio mass to biofue l can significantly reduce the country’s dependence oncrude oil imports, enhance nationa l security. Therefore, the use of lignocellulosic toproduce fue l etha nol in China has important economic and socia l significance.The lignocellulose resources in China is very ric h, but the utilization is very low,mostly in d irect use as a fue l, not only wasting resources and pollut ing theenvironme nt serious ly. So the develop ment of using lignocellulose to product fue lethano l in China has broad prospects and important practica l significance. In thisthesis, in order to investigate the degradation process of natura l lignocellulose, wheatstraw and birch wood chips were chosen to be as representive raw materia ls ofherbaceous and woody plants.In order to investigate the effect on the degradatio n of the natura l lignocellulos icsubstrates (wheat straw and birc h wood chips) with the phys ical degradation method(ball milling and ultrasonic treatme nt), chemica l acid hydro lys is method, bio logica ldegradatio n method, and the synergy between these three methods, the wheat strawand birch wood chips were hydrolyzed by wet ball milling, d ilute c itric ac id,Penicillium simplicissimum H5and ultrasonic treatme nt. Exp lore the feas ib ility o fdegradatio n of natura l lignocellulos ic substrates (wheat straw and birch wood chips)under norma l temperature and pressure. It is expected that there is a simp le, andenvironme nta lly friend ly approach for hydrolyzing wheat straw and birc h wood chipsto sugar. Firstly, the wheat straw and birch wood chips were hydrolyzed by thecomb ination o f wet ball milling and d ilute c itric acid, to research the e ffect of the pHvalue on the hydrolys is of wheat straw and birc h wood chips. Secondly, Penicilliumsimplicissimum H5was used to improve the hydro lys is, us ing its enzyme productioncharacteristics. The wheat straw and birch wood chips were hydrolyzed by thecomb ination of wet ball milling, dilute citric acid and Penicillium simplicissimum H5,to research the effect of the Penicillium simplicissimum H5on the hydro lys is of wheatstraw and birch wood chips. At last, the ultrasound was introduced into the reactionsystem. The birch wood chips was pretreated by ultrasonic treatment, the n werehydro lyzed by the comb inatio n of wet ball milling, dilute c itric acid and Penicillium simplicissimum H5, to research the effect o f ultrasonic treatment a nd the pH va lue onthe hydro lys is of wheat straw and birch wood chips.In the first p lace, the wheat straw and birch wood chips can be hydro lyzed by thecomb ination of wet ball milling and dilute c itric acid, under norma l te mperature andpressure.(1) The sugar production of wheat straw and brich wood were186.9mg/gand120.5mg/g.(2) The addition o f commerc ia l cellulase can not form a goodsynergy with the wet ball milling-dilute c itric acid treatme nt. The sugar productionwas even lower than s ingle the wet ball milling-dilute citric ac id treatment withoutce llulase.(3) Ball milling with dilute ac id treatme nt exerted significant differentinflue nce on the different hydro lysates. The yie ld of glucose increased with extend ingball milling time in the hydrolys is of wheat straw and wood chip s, otherwise the yie ldof xylose decreased with exte nd ing ball milling time. The hydrolys is of wood can alsobe influe nced by the pH va lue of d ilute acid. The sugar production in c itrate solve nt(pH=5,6) were higher tha n in c itrate solvent (pH=3,4).(4) With the extend ing ballmilling time, the pH va lue of wheat straw and wood chips’ hydrolyzate offset to thealkaline direction and reach equilibrium after24hours. Finally rema ined substantia llywithin the neutral ra nge.(5) As was shown in the XRD a nd ESEM pattern, ballmilling disrupted the long-range crystalline structure of cellulose. It made wheatstraw and wood chips more accessib le to citrate, which enab ling convers ion ofcarbohydrate polymers into sugar.(6) The FT-IR and UV spectroscopy ind icated thatthe ball milling treatme nt in citrate solvent present a dramatic increase in ligninhydro lys is. As the connection between the lignin and carbohydrates serious ly impededto the hydro lys is of lignocellulos ic, the degradation of lignin make cellulasehydro lyzed more easily and reach higher sugar production. Compared with trad itiona lindustria l high-temperature and high-pressure acid hydrolys is, the comb ination of wetball milling and dilute citric acid treatment can hydrolyze natura l lignocellulose undernorma l te mperature and pressure. Although the saccharification is not high, thereactio n is mild and basica lly non-polluting.Secondly, the hydrolyzation of wheat straw and birc h wood chips can besignifica ntly promoted by the comb inatio n of wet ball milling,dilute citric acid andPenicillium simplicissimum H5, under norma l te mperature and pressure and reachhigher sugar yie ld.(1) The sugar production o f wheat straw and brich wood were216.9mg/g and245.3mg/g. The addition of Penicillium simplicissimum H5couldsignifica ntly pro mote the hydrolys is o f wheat straw and wood chips.(2) The add itionof Penicillium simplicissimum H5can form a good synergy with the wet ball milling and dilute citric acid treatment. The enzyme activity and surviva l of fungi ma inta in24hours under ball milling treatment.(3) Ball milling-dilute acid-fungi treatme ntexerted significant different influe nce on the differe nt hydro lysates. The yie ld ofglucose increased with extend ing ball milling time in the hydrolys is of wheat strawand wood chips, otherwise the yie ld of xylose decreased with e xtend ing ball millingtime. The hydro lys is of wood can also be influenced by the addition of Penicilliumsimplicissimum H5. The sugar production in citrate solve nt (pH=4,5) were higher tha nin citrate solvent (pH=3,6).(4) With the extend ing ball milling time, the pH va lue ofwheat straw and wood chips’ hydrolyzate offset to the alka line d irection a nd reachequilibrium a fter24hours. The pH va lue o f t he best degradatio n syste m o f straw andwood chips were6.5and7.5after ba ll milling48hours.(5) As was shown in the XRDand ESEM pattern, ball milling-dilute acid-fungi treatment disrupted the lo ng-rangecrystalline structure of cellulose. At milling short time, the degree of crysta llinity ofthe straw and wood chips improved, as the addition of Penicillium simplicissimum H5decomposed amorphous cellulose for priority. With the extending ball milling time,the crystallinity decreased. It made wheat straw and wood chips more accessib le tocitrate, whic h enabling convers ion of carbohydrate polymers into sugar.(6) The FT-IRand UV spectroscopy ind icated that the ba ll milling treatme nt in c itrate solve ntpresent a dramatic increase in lignin hydrolysis. The addition o f Penicilliumsimplicissimum H5Promoted the degradatio n of lignin in the wheat straw and woodchips.As the connection between the lignin and carbohydrates serious ly impeded tothe hydrolys is of lignocellulosic, the degradatio n of lignin make cellulase hydrolyzedmore easily a nd reach higher sugar production. Overall the additio n of Penicilliumsimplicissimum H5Significant promoted the degradatio n of ce llulose and lignin o fwheat straw and wood chips, reach higher saccharification. The reactio n is mild andbasica lly non-po lluting, low cost with microbia l and ease for ind ustrialization.Fina lly, birch wood chips was pretreated by ultrasonic treatment, then werehydro lyzed by the comb ination of wet ball milling, dilute c itric acid and Penicilliumsimplicissimum H5, and the hydrolyzation can be significa ntly promoted by thepretreatment of ultrasonic wave, and reach higher sugar yie ld.(1)The sugarproductio n of wood chips was126.84mg/g with the ultrasonic pretreatme nt.(2) Theadditio n of ultrasonic pretreatment could s ignificantly promote the hydrolys is ofwood chips, and reach higher saccharification rate. The sugar production of woodchips was311.16mg/g wood at ball milling for36hours, compared with245.3mg/gwood at ball milling for48hours obtained without the ultrasonic pretreatme nt.(3) Ultrasonic pretreatment could promote the d issolution o f both glucose and xylose.(4)After pretreated by the ultrasonic wave, with the extend ing ball milling time, the pHvalue of wood chips’ hydro lyzate offset to the alka line direction and reachequilibrium after12hours. The pH va lue of the best degradatio n system of woodchips were7.0after ball milling48hours.(5) As was shown in the XRD and ESEMpattern, ball milling-dilute acid-fungi treatment disrupted the long-range crystallinestructure of cellulose. The ultrasonic pretreatment s lightly decreased the degree ofcrystallinity of wood chips. At milling short time, the degree of crystallinity of thewood chips improved, with the addition of ultrasonic pretreatme nt. With theextend ing ball milling time, the crysta llinity decreased. It made wood chips moreaccessib le to citrate, which enabling convers ion of carbohydrate polymers into sugar.(6) The FT-IR and UV spectroscopy indicated that the ball milling treatment in citratesolve nt with H5present a dramatic increase in lignin hydrolys is. The additio n ofultrasonic pretreatment promoted the degradation of lignin in the wood chips. As theconnectio n between the lignin and carbohydrates serious ly impeded to the hydrolys isof lignocellulosic, the degradatio n of lignin make cellulase hydrolyzed more easilyand reach higher sugar production. Overall the additio n of ultrasonic pretreatme ntsignifica nt promoted the degradation of ce llulose and lignin of wood chips, reachhigher saccharification. The reactio n is mild and basically no n-polluting, low costwith microbia l and ease for industria lization.In summary, in this thes is the natura l lignocellulose wheat straw and birchwood chips were hydrolyzed by the comb ination o f wet ball milling, dilute c itric acid,Penicillium simplicissimum H5and ultrasonic treatment, reach high saccharificationrate. The reactio n is mild and basically non-polluting, low cost with microbia l andease for industria lization, and provides a clean, effic ient and new way for conversio nof bio mass into ethano l.更多还原