【作者】 乌日娜；

【导师】 何北海；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2014， 博士

【摘要】 为了进一步节约水资源、节约原料、减少污染，造纸白水封闭循环程度不断提高，导致其中的DCS物质不断积累，给整个造纸系统带来严重的影响。本论文针对DCS中阴离子垃圾的主要贡献组分之一，果胶类物质，采取了生物中的固定化酶方法对其进行定向处理。论文中使用浆料纤维和再生纤维素微球两种载体，通过几种不同的简易、温和、低成本的方法，制备出固定化果胶酶。对制备固定化酶的过程和固定化酶的性质进行了研究，并考察了其降低实际造纸生产中DCS的阳离子需求量的效果。以高碘酸钠法氧化得到的氧化针叶木浆料纤维为原料，通过希弗碱反应，得到以浆料纤维为载体的共价结合表面搭载法制得的固定化果胶酶。选用浓度为25.0g/L的高碘酸钠氧化30min得到的氧化纤维来固定酶，此条件下得到的氧化浆料纤维醛基含量较高，且纤维降解不严重。在固定化温度20℃，酶液pH值7.0，酶浓度为0.125%时，得到的固定化酶活力可达到65U/g左右。与游离酶相比，固定化酶在更宽的温度和pH范围内保持较高的活性，最适宜pH由8.0变为8.8，连续使用6次后，仍能保持约60%的初始酶活力。在定向处理造纸生产中的DCS时，能将其阳离子需求量降低37%，基本将其中聚半乳糖醛酸全部降解，并在使用6次后仍能降低15%。使用造纸过程中一种常见的化学添加剂-聚乙烯亚胺，来涂覆浆料纤维，再以其作为载体通过离子吸附等作用力将酸性果胶酶固定上。使用聚乙烯亚胺涂覆浆料后充分洗涤，并在固定化酶后不加戊二醛交联，可得到酶活力更高的固定化酸性果胶酶。当PEI浓度、酶稀释液浓度和酶液pH值分别为0.01%(w/v)，0.25%(v/v)和7.0时，得到的酶活力最大，约为670U/g。在此条件下，PEI与果胶酶的负载量分别为1.1mg/g绝干浆料纤维和36.4mg/g绝干浆料纤维。与游离酸性果胶酶相比，PEI-涂覆浆料纤维固定化酸性酶的最适pH值由3.5移向4.0，最适使用温度提高，并且有更宽的pH和温度适用范围，具有更好的稳定性和更高的催化分解速率。另外，固定化酶活化能明显下降，其催化果胶分解速率对温度的敏感性降低。在定向处理造纸DCS降低其阳电荷需求量方面，PEI-涂覆浆料纤维固定化酸性果胶酶在连续使用7次后仍有一定的效果。以LiCl/DMAC溶剂体系来溶解微晶纤维素，通过简单的滴加方法制备直径1-2mm呈规则的球状的再生纤维素球，对其性质进行了研究。再生纤维素微球表面多孔，内部形成一种三维立体网络结构，具有较大的比表面（108m2/g），是良好的载体或吸收剂。再生纤维素微球仍为纤维素I型结晶态，并且仍为Iβ主导型，但是结晶度大幅度下降。再生纤维素微球具有较好的热稳定性。果胶酶在再生纤维素微球上的等温吸附，符合Langmuir吸附方程，这表明酶分子在再生纤维素微球上的吸附过程是均匀的单层吸附，并且该吸附过程是自发的、易达到吸附平衡的，其最大吸附量为7.39mg/g。另外，再生纤维素球对果胶酶的吸附动力学，符合准二级动力学方程，化学吸附是控制吸附速率的主要因素。这为使用再生纤维素微球在诸如生物等领域作载体及吸收剂提供了理论支持。以再生纤维素微球为载体，分别使用物理吸附法和共价结合法制备出固定化果胶酶。使用物理法时，固定化温度、时间和酶稀释液的pH值分别为20℃，2h和7.0时，得到的酶活力最大，为178U/g固定化酶，蛋白质负载量为2.9mg/g。使用共价结合法制得酶活力100U/g、蛋白质负载量6.7mg/g的固定化果胶酶。与游离果胶酶相比，二者的稳定性均提高，并且都能将漂白塔后浆料滤液的阳离子需求量降低36%左右。共价结合法制得的固定化酶有更好的重复使用性能。除此之外，当重复使用多次后，再生纤维素微球仍保持良好的机械强度，可以再次作为酶的载体使用。更多还原

【Abstract】 In order to reduce water consumption, economize on raw materials and reduce pollution,it is demanded that the whitewater in papermaking process should be increasingly recycled.Consequently, dissolved and colloid substances accumulate in the system, leading to seriousproblems. In this dissertation, immobilized enzyme was used to deal with pectic substances,one of the major contributions to anionic trash. Pulp fiber in papermaking and regeneratedcellulose beads were utilized as carrier for pectinase via simple, facile and inexpensivemethods, respectively. The preparation and the properties of the resultant enzymes werestudied. Besides, they were tested for reducing cationic demand of practical DCS.Pulp fiber was oxidized using NaIO4and then pectinase was coupled on it through Schiffbase reaction. Oxidized pulp fiber by25.0g/L NaIO4for30min was chosen for its relativelyhigh aldehyde content and minor degradation. The enzymatic activity of immobilizedpectinase on pulp fiber reached65U/g when immobilization pH value, temperature and timewere of7.0,20℃and15min, respectively. The immobilized pectinase showed higherthermo stability in a wider temperature range of40–70℃than its free type and its optimalpH shifted from8.0to8.8. About60%of the original activity was maintained after theimmobilized pectinase was used6times. When employed in DCS treatment of papermakingindustry, it reduced the cationic demand by37%, meaning almost all of the polygalacturonicacid depolymerized. Moreover, it still decreased the cationic demand by15%after operatingrepeatedly for6batches.Polyethyleneimine is a common used additive in papermaking process. It was used tocoat pulp fiber to produce PEI-coated fiber, which was then employed to immobilize acidicpectinase through ionic adsorption. Immobilized pectinase with higher activity could beobtained if the pulp fiber was thoroughly washed after being coated with PEI and noglutaraldehyde was added for crosslinking. When PEI concentration, enzyme concentrationand pH of enzyme solution were0.01%(w/v),0.25%(v/v) and7, respectively, the resultantimmobilized enzyme exhibited the highest enzymatic activity as about670U/g. The PEIloading and protein loading under the condition were1.1mg/g and36.4mg/g, respectively. Higher thermo and pH stabilities than those of the free enzyme were achieved afterimmobilizing the enzyme on PEI-coated pulp fiber with its optimal pH shifting from3.5to4.0. Furthermore, the bound pectinase depolymerized pectin with a higher rate. Its loweractivatioin energy meant that the catalytic rate was less sensitive to temperature. On top ofthat, the immobilized pectinase effectively decreased the cationic demand of DCS inpapermaking under the practical industrial conditions and still maintained activity afteroperating repeatedly for7batches.Porous cellulose beads were prepared through a simple dripping method after dissolvedin LiCl/N, N-Dimethylacetamide. The resultant microspheres exhibited good spherical shapewith a diameter of1-2mm. Their morphology, pore structure, and physical properties werecharacterized. The regenerated cellulose was shown to have a three-dimensional porousstructure, which led to a BET surface area of as large as108m2/g. This may be useful asadsorbents or carriers. Besides, the resultant bead cellulose remained cellulose Ⅰ structureand good thermo stability. The regenerated cellulose maintained Iβtype with substaintaillylower crystalinity. Finally, the cellulose beads were tested in adsorption of pectinase. It wasrevealed that the adsorption was a favorable spontaneous process. Moreover, analysis resultsshowed that the adsorption was in well agreement with Langmuir isotherm with a capacity of7.39mg/g, which meant that pectinase adsorption was a monolayer sorption. It can also beconcluded from the kinetics study that the adsorption followed a pseudo-second-order kineticmodel in the overall process, indicating that chemisorptions were the rate controllingmechanism. This will provide information for the potential utilization of the regeneratedcellulose microspheres as support for enzyme in biotechnology and biochemistry field.Pectinase was immobilized on regenerated cellulose beads using physical adsorption andcolavent binding, respectively. By adsorption, the optimum immobilization temperature, timeand pH of the immobilized pectinase on regenerated cellulose beads were20℃,2h and7.0,respectively, under which the enzyme showed high protein loading and enzymatic activity of2.9mg/g and178U/g of the immobilized biocatalyst, respectively. On the other hand, thecolavently immobilized pectinase showed6.7mg/g and100U/g. Compared with the free pectinase, both kinds of the immobilized enzyme showed higher thermo and pH stabilities andeffectively lowered the cationic demand of slurry filtrate by36%. Besides, the immobilizedenzyme obtained through chemical reaction had better reusability. Furthermore, theregenerated cellulose beads maintained good mechanical strength after several batches andcould be resued as support.更多还原