Cellulase retention and sugar removal by membrane ultrafiltration during lignocellulosic biomass hydrolysis

Technologies suitable for the separation and reuse of cellulase enzymes during the enzymatic saccharification of pretreated corn stover are investigated to examine the economic and technical viability of processes that promote cellulase reuse while removing inhibitory reaction products such as glucose and cellobiose. The simplest and most suitable separation is a filter with relatively large pores on the order of 20–25 mm that retains residual corn stover solids while passing reaction products such as glucose and cellobiose to form a sugar stream for a variety of end uses. Such a simple separation is effective because cellulase remains bound to the residual solids. Ultrafiltration using 50-kDa polyethersulfone membranes to recover cellulase enzymes in solution was shown not to enhance further the saccharification rate or overall conversion. Instead, it appears that the necessary cellulase enzymes, including β-glucosidase, are tightly bound to the substrate; when fresh corn stover is contacted with highly washed residual solids, without the addition of fresh enzymes, glucose is generated at a high rate. When filtration was applied multiple times, the concentration of inhibitory reaction products such as glucose and cellobiose was reduced from 70 to 10 g/L. However, an enhanced saccharification performance was not observed, most likely because the concentration of the inhibitory products remained too high. Further reduction in the product concentration was not investigated, because it would make the reaction unnecessarily complex and result in a product stream that is much too dilute to be useful. Finally, an economic analysis shows that reuse of cellulase can reduce glucose production costs, especially when the enzyme price is high. The most economic performance is shown to occur when the cellulase enzyme is reused and a small amount of fresh enzyme is added after each separation step to replace lost or deactivated enzyme.     

基于聚合物点的电致化学发光生物传感器用于葡萄糖检测

羧基功能化的聚[(9,9-二辛基芴基-2,7-二基)-co-(1,4-苯并-{2,1′,3}-噻二唑)]聚合物点(PFBT-COOH)在无外加共反应试剂的条件下具有高的电致化学发光(ECL)信号,且过氧化氢(H_2O_2)对其ECL具有高效猝灭作用。采用PFBT-COOH修饰玻碳电极,进一步交联葡萄糖氧化酶(GOD)以构建酶传感器(GOD/PFBT-COOH/GCE)。随着检测底液中葡萄糖浓度的增加,葡萄糖在GOD催化下原位产生的H_2O_2量增加,导致传感器的ECL信号逐渐减弱,从而实现葡萄糖的准确、快速、灵敏检测。此方法测得葡萄糖的线性范围为1.0×10~(-7)～3.0×10~(-3) mol/L,检出限为3.0×10~(-8) mol/L。血清样品中葡萄糖的加标回收率为98.5%～106%。该策略为酶传感器的构建提供了新思路,为葡萄糖的检测提供了新方法。     

Electrochemical response of ascorbic acid at conducting and electrogenerated polymer modified electrodes for electroanalytical applications: a review

The present short review deals with electroanalytical aspects of electrochemical response of ascorbic acid (Vitamin C) at conducting and electrogenerated polymer modified electrodes. Two main topics are considered: (i) electrocatalytic oxidation of ascorbate at conducting polymer modified electrodes, leading to electroanalytical techniques for ascorbate assay, and (ii) retardation of ascorbate penetration through a layer of electrogenerated polymers, leading to permselective coatings and their diverse uses, especially for biosensing devices.     

电聚合吡咯膜修饰的葡萄糖氧化酶电极

自制的铂丝电极经铂化处理后,将葡萄糖氧化酶与单体吡咯用循环伏安法共聚合到电极上,铂化后电极表面积的增大增加了固定的酶量,同时也增大了电极对Ｈ２Ｏ２的催化能力,使电极对葡萄糖的响应电流增大到７．５ｍＡ／（ｍｏｌ·Ｌ＾－１）,还测试了聚合液中酶浓度、ｐＨ值和聚合时间等因素对电极特性的影响。     

再生丝心蛋白和羧甲基纤维素复合膜的特性及其在有机相葡萄糖生物传感器中的应用

用再生丝心蛋白和羧甲基纤维素构成的复合膜作为固定葡萄糖氧化酶的基质,并用红外光谱测试了该复合膜的结构,用扫描电子显微镜观察了其形态．用上述复合膜材料固定葡萄糖氧化酶和羧酸二茂铁（或７,７,８,８－四氰代二甲基苯醌,ＴＣＮＱ）制成的葡萄糖生物传感器具有较好的灵敏度与稳定性     

葡萄糖氧化酶及过氧化氢酶的生物合成

研究了黑曲霉细胞的生长及其葡萄糖氧化酶、过氧化氢酶的生物合成．ＣａＣＯ３是２种酶的产酶诱导因子,其产酶模式都是延续合成型,最大比生长速度μｍａｘ、菌体得率Ｙ（Ｘ／Ｓ）、葡萄糖氧化酶及过氧化氢酶合成得率Ｙ（ＧＯＤ／Ｓ）、Ｙ（ＣＡＴ／Ｓ）分别为０．０９７ｈ－１、０．０７５ｇ．ｇ－１、２９．３４μｍｏｌ·ｍｉｎ－１·ｇ－１、３８９．１７μｍｏｌ·ｍｉｎ－１·ｇ－１．也研究了各种物质对葡萄糖氧化酶及过氧化氢酶活力的影响,金属离子对葡萄糖氧化酶有抑制,阴离子对葡萄糖氧化酶和过氧化氢酶有抑制,还原性小分子化合物是葡萄糖氧化酶的激活剂     

小毛足鼠(Phodopus roborovskii)食性和食量的研究

小毛足鼠饲喂试验结果以及颊囊食物统计结果表明,该鼠在饲喂条件下食物资源利用谱相对较宽,但在野外条件下食物资源的利用主要以植物种子为主;并结合具体情况探讨了造成野外条件下该鼠食物资源利用范围趋于特化的原因．估算了小毛足鼠的采食效率为０．０７６％～０．１４％．在以上研究基础上,对小毛足鼠的危害与防治问题作了初步分析与说明     

Ferrocene-Nafion修饰厚膜碳糊电极的葡萄糖传感器研究

以基于丝网印刷技术制作的厚膜碳糊电极为基底电机,用二茂铁为介体、Nafion修饰厚膜碳糊电极制备了葡萄糖传感器．Nafion涂于电极表面上形成的膜具有强的附着力,防止了二茂铁及酶的流失,电极稳定性提高．并且由于低的工作电位（＋025vsSCE）和Nafion膜的阳离子交换作用,基本上消除了电活性物质（抗坏血酸、尿酸）的干扰,具有防污能力．该酶传感器的检测上限可达18mmol／L,响应时间小于60s.     

葡萄糖氧化酶电极的制备

葡萄糖氧化酶电极的制备于秀娟，周定，郭京华（哈尔滨工业大学应用化学系哈尔滨１５０００６）关键词葡萄糖氢化酶，酶电极，制备酶与电极的连接即酶膜的形成是制备酶电极的关键步骤之一，有许多种方式［１～９］．葡萄糖氧化酶（ＧＯＤ）电极是研究较早和报道较多的一类...     

Comparison of different strains of the yeastYarrowia lipolytica for citric acid production from glucose hydrol

Four commercial strains and two mutants of the yeast species Yarrowia lipolytica were screened using batch fermentation. Strain Y. lipolytica A-101-1.14 (induced with UV irradiation) was found to be the most suitable for citric acid production from glucose hydrol (39.9% glucose and 2.1% other sugars), a byproduct of glucose production from potato starch. The specific rate of total citric and isocitric acid production was 0.138 g/g.h, the yield on consumed glucose 0.93 g/g, and the productivity achieved was as high as 1.25 g/L.h. All of the tested yeast strains were able to utilize only the glucose from the glucose hydrol medium. Thus, some residual higher oligosaccharides remained in the process effluent.