离子液体预处理纤维素及木质纤维素的研究进展

稳定性好、溶解能力强的离子液体,能够快速瓦解木质纤维素网络结构,提高纤维素酶的可及度和酶解效率,可大幅度降低预处理成本。本文综述了常见离子液体的组成、离子液体对木质纤维素的溶解分离等预处理方法及其原理。     

餐厨垃圾与秸秆混合中温和高温厌氧消化对比

餐厨垃圾与秸秆混合厌氧消化可有效改善两者单独厌氧消化易出现的挥发性脂肪酸积累和木质纤维素难以降解等问题,并回收生物质能.在中温(35℃)和高温(55℃)条件下,对餐厨垃圾与秸秆混合厌氧消化进行了序批式试验研究.结果表明,进料的挥发性固体(VS)浓度为3 kg·m~(-3),中温条件下,物料进料比(VS/VS)为9∶1时,单位有机负荷累积甲烷产量达到最高,为272.0 mL·g~(-1);高温条件下,进料比为5∶5时,单位有机负荷累积甲烷产量达到最高,为402.3 mL·g~(-1),分别显著高于两温度条件下餐厨垃圾单独厌氧消化的结果(中温218.6 mL·g~(-1),高温322.0 mL·g~(-1)).高温条件下物料中的碳流向甲烷的比例高于中温,且两物料混合消化促进碳流向甲烷.高温下木质纤维素总降解率为34.7%~45.8%,高于中温的12.6%~42.2%.利用高通量测序技术检测细菌与古菌的16S rRNA基因序列信息和真菌的内转录间隔(ITS)序列信息,结果表明,高温下木质纤维素降解细菌和放线菌数量明显高于中温条件,可解释高温下木质纤维素总降解率更高的原因.     

纤维素基吸附剂——绿色、经济的水处理材料

介绍了一类基于天然纤维素的水处理用吸附剂.对纤维素修饰羧基等阴离子基团,可以用来吸附水中的重金属阳离子(如cd(2+)、Cu(2+)、Hg(2+)、Ni(2+)、Pb(2+).对纤维素修饰铝铁或胺基等成分,可以吸附水中含砷阴离子、氟离子等有害阴离子.在纤维素上修饰疏水链,可以吸附水中氯苯、染料等危害健康的有机物.     

Continuous live cell imaging of cellulose attachment by microbes under anaerobic and thermophilic conditions using confocal microscopy

Live cell imaging methods provide important insights into the dynamics of cellular processes that cannot be derived easily from population-averaged datasets.In the bioenergy field,much research is focused on fermentation of cellulosic biomass by thermophilic microbes to produce biofuels;however,little effort is dedicated to the development of imaging tools to monitor this dynamic biological process.This is,in part,due to the experimental challenges of imaging cells under both anaerobic and thermophilic conditions.Here an imaging system is described that integrates confocal microscopy,a flow cell device,and a lipophilic dye to visualize cells.Solutions to technical obstacles regarding suitable fluorescent markers,photodamage during imaging,and maintenance of environmental conditions during imaging are presented.This system was utilized to observe cellulose colonization by Clostridium thermocellum under anaerobic conditions at 60℃.This method enables live cell imaging of bacterial growth under anaerobic and thermophilic conditions and should be widely applicable to visualizing different cell types or processes in real time.     

氨基修饰氧化石墨烯-羧甲基纤维素复合吸附剂的制备及其对Cr (VI)的吸附性能研究

为获得价格低廉、吸附性能优良的石墨烯基吸附剂,以氧化石墨烯（GO）、羧甲基纤维素（CMC）为基材,以聚乙烯亚胺（PEI）为改性试剂,通过化学修饰的方法制备了氨基修饰氧化石墨烯-羧甲基纤维素复合吸附剂（GO-PEI-CMC）.采用扫描电镜（SEM）、傅里叶红外光谱（FT-IR）及X射线光电子能谱（XPS）等表征手段证实了CMC、氧化石墨烯与PEI已成功复合.静态吸附实验表明GO-PEI-CMC对Cr （VI）表现出良好的吸附性能,由Langmuir等温吸附模型所得最大吸附量值为243.92 mg·g^-1.吸附动力学、吸附等温线研究表明GO-PEI-CMC对Cr （VI）的吸附为单分子层、化学吸附过程.GO-PEI-CMC对Cr （VI）吸附性能优良,且具有绿色环保、可生物降解的优点,是一种极具潜力的Cr （VI）吸附剂.     

Advances in the study of directed evolution for cellulases

If cellulose can be effectively hydrolyzed into glucose by cellulase, the production costs of hydrogen, ethanol or other chemicals from cellulosic materials will be greatly decreased, and economically viable production of biohydrogen and bioethanol will become feasible. Cellulose is degraded into glucoses by multi-component enzyme systems. Nowadays cellulases are widely used in brewing, food, bioenergy, fodder, textiles, paper, pharmaceuticals, environmental protection and other industries. However, existing cellulases have several problems that limit their wider applications, including the low turnover number for solid cellulosic materials, and low stability in adapting to various application conditions. For example, high temperature, low pH, and so on. Application of directed evolution technology may be one of the most effective ways for improving the characteristics of cellulases. This paper presents a brief review of the cellulose hydrolysis mechanism by cellulase, advances in cellulases (endoglucanase and β-glucosidase) improvement by directed evolution for several characteristics (for instance, thermal stability, pH adaptability and enzyme activity), limitations of directed evolution for cellulases, and the outlook for directed evolution for cellulase.     

改性羧甲基纤维素对铀吸附机理的试验研究

对羧甲基纤维素(CMC)进行改性,并将其用于吸附废水中的铀.研究结果表明:在温度为70℃~80℃、单体质量浓度为30%~35%、羧甲基纤维素:丙烯酸(质量比)为10:2.5、反应时间为3.5~4h条件下,CMC改性效果最好;在改性CMC质量浓度为0.10g/L,温度为25℃, pH值为5.0,反应时间60min的条件下,对废水中铀去除率达到了97.1%;改性CMC对溶液中U(VI)的吸附过程符合Freundlich方程,其吸附动力学数据符合准一级方程(R2=0.9618),表明改性CMC的吸附主要是表面吸附;热力学研究表明,改性CMC对铀的吸附吉布斯自由能(ΔG0)0,吸附过程是自发的吸热反应、以物理吸附为主的过程.     

膜生物膜工艺处理含盐工业废水

采用了膜生物膜工艺处理含盐羧甲基纤维素生产废水。接种污泥为普通污泥,经驯化使其适应含盐废水,在污泥驯化阶段,生物膜表现出极佳的盐度冲击后恢复能力。通过较长的水力停留时间(5～15 d)和较低的COD有机负荷(平均1.6 kg/(m3·d)左右),生物膜COD去除率基本达90%。膜池内,悬浮固体浓度基本保持在5 000 mg/L以内;通过聚偏氟乙烯中空纤维膜过滤,出水悬浮固体浓度保持在5 mg/L以内。膜污染可通过重复的气水反洗和定期的化学清洗得以缓解。     

Thermal radiation hazards and separation distances for industrial cellulose nitrate

Many forms of industrial cellulose nitrate burn fiercely with the emission of large quantities of thermal radiation. Models are considered for predicting the variation with distance of the irradiance from burning cellulose nitrate. These models are evaluated using data from HSE and German trials. An approach to setting quantity safety distances for cellulose nitrate is given.     

Alkaline Degradation of Cellulose: Mechanisms and Kinetics

Cellulose powder and softwood sawdust were subjected to alkaline degradation under conditions representative of a cementitious environment for periods of 7 and 3 years, respectively. During the first 3 years, sampling was frequent, and data on the degradation of cellulose and production of isosaccharinic acid was used for establishing long-term prediction models. Samples after an additional period of 4 years were compared to the predicted values. The total rate of degradation was measured as the increase in total organic carbon (TOC) in corresponding solutions. A previously published theoretical model of degradation kinetics gave a good approximation of the present experimental data. Peeling-off, stopping, and alkaline hydrolysis reaction rate constants were obtained as model parameters, and the results suggested that the transformation of the glucose end group is the rate-limiting step in the cellulose peeling-off reaction and also determines the pH dependence of that reaction. After 3 years, isosaccharinic (ISA) acid represented 70–85% of all degradation products as quantified by capillary zone electrophoresis. The long-term prediction model indicated that all of the cellulose would be degraded after only 150–550 years. The control sampling after 7 years points toward a lower degradation of cellulose and production of ISA than predicted by the model, reflecting either a degradation of ISA that was faster than the production or a termination of the ISA production.