Investigations of cell immobilization in alginate: rheological and electrostatic extrusion studies

In this study, the process of electrostatic extrusion as a method for cell immobilization was investigated. We have assessed the effects of concentrations of yeast cells (as a model cell type) and Na alginate on the size of the resulting microbeads and attempted to rationalize the obtained findings by rheological characterization of the cell–alginate suspensions. Under the investigated conditions, microbeads, 50–600 µm in diameter, were produced and the increase in both alginate and cell concentrations resulted in larger microbeads with their sizes having higher standard deviations. Rheological characterization revealed non‐Newtonian, pseudoplastic behavior of cell–alginate suspensions with higher viscosities at higher alginate concentrations. However, the presence of cells even at high concentrations (5 × 10⁸ and 1 × 10⁹ cells mL^?1) did not significantly affect the rheological properties of the Na alginate solution. Finally, we have investigated the kinetics of alginate gelation with respect to the quantity of Ca²⁺ ions and the presence of cells. The molar ratio of α‐L ‐guluronic acid units to Ca²⁺ ions of 4:1 provided complete crosslinking. The presence of cells decreased the rate of network formation as well as the strength of the obtained Ca alginate hydrogel. Copyright © 2006 Society of Chemical Industry     

一种嗜热嗜碱过氧化氢酶的分离纯化和固定化

引言过氧化氢酶(catalase,简称CAT,EC1.11.1.6)是一种高效催化分解过氧化氢的酶,广泛存在于好氧微生物和动植物体内。在纺织印染工业、造纸工业、废水处理、纸浆、牛奶保鲜以及临床分析等方面有着广泛的应用[1-3]。     

A novel method for immobilization of chitosan onto nonporous glass beads through a 1,3-thiazolidine linker

A new method for the surface modification of nonporous glass beads (average diameter, 6 μm), which characterized by formation of a 1,3-thiazolidine ring between l-cysteine linkers on the glass bead and reducing ends of chitosan, has been developed. γ-Aminopropyltriethoxysilane (APES)-treated glass bead was first subjected to condensation with an l-cysteine derivative, l-4-carboxy-3-formyl-2,2-dimethylthiazolidine (CFMT), in the presence of water-soluble carbodiimide hydrochloride (WSC) and HOBt. After deprotection by diluted hydrochloric acid, the glass beads with activated cysteine linkers on the surface were treated with reducing chitosan in aqueous acetic acid solution at room temperature. The maximum content of chitosan immobilized on the glass beads estimated by acid-hydrolysis and subsequent glucosamine analysis by Svennerholm method after was 0.73% (w/w). This was obtained by using chitosan having an average molecular weight of 14 kD. Model reactions of the cysteine derivatives with reducing chitosan were also performed and the product was examined by IR and NMR spectroscopy to verify the linkage between cysteine and chitosan.     

Simultaneous purification and immobilization of bitter gourd (Momordica charantia) peroxidases on bioaffinity support

This paper demonstrates the construction of an inexpensive bioaffinity adsorbent by simply incubating Sephadex G 50 matrix with jack bean meal extract at room temperature. Sephadex G 50 adsorbed 17 mg Con A (concanavalin A) per g of the matrix. Con A‐adsorbed Sephadex was employed for the immobilization of glycoenzymes directly from ammonium sulfate‐fractionated proteins of bitter gourd. The obtained bioaffinity support was very efficient for high yield immobilization of peroxidases from bitter gourd and it bound nearly 425 enzyme units per g of the matrix. Bitter gourd peroxidase immobilized on lectin–Sephadex support showed a very high effectiveness factor, ‘η,’ of 1.25. Immobilized BGP preparation was quite stable against the denaturation induced by pH, heat, urea, Triton X 100, Tween 20, SDS, Surf Excel and water‐miscible organic solvents: dimethyl sulfoxide and dimethyl formamide. Low concentration of detergents like SDS, Tween 20, and Triton X 100 enhanced the activity of soluble and immobilized bitter gourd peroxidase. Peroxidase bound to the bioaffinity support exhibited very high resistance to proteolysis caused by the trypsin treatment. Con A–Sephadex‐bound bitter gourd peroxidase retained 85% of its initial activity after treatment with 2.5 mg trypsin per cm³ of incubation mixture for 1 h at 37 °C while the soluble enzyme lost nearly 40% of the initial activity under similar incubation conditions. Immobilized bitter gourd peroxidase preparation appeared to be more rigid to proteolysis mediated by trypsin compared with soluble bitter gourd peroxidase. Copyright © 2004 Society of Chemical Industry     

A simple rate model for the dynamics of immobilization of anaerobic bacteria on a plastic support

The dynamics of biofilm formation on polyethylene bioparticles in mesophilic anaerobic conditions, using an inverse fluidized bed as immobilization system, have been studied. The immobilization process was carried out using acetate and glucose as carbon sources. Scanning electron microscopy (SEM) showed cocci cells and Methanosaeta rods embedded into an exopolimeric substances (ESP) matrix. The acetoclastic activity was found to increase as soon as the lag biomass accumulation phase ended. The rate of immobilization was found to conform to a pseudo first order kinetics with good correlation. This kinetic model was used to estimate rate and equilibrium constants for the immobilization process. Rate properties have been explained in terms of attachment and detachment processes. © 2000 Society of Chemical Industry     

固载化L-脯氨酸及其衍生物的最新研究进展

近年来，固载化L-脯氨酸及其衍生物手性催化剂因其具有均相催化剂的高活性和高选择性以及非均相催化剂的高循环使用性，被广泛用于催化不对称有机化学反应。本文简单介绍了L-脯氨酸及其衍生物的种类，包括4-羟基-L-脯氨酸、脯氨醇醚类等；重点阐述了固载L-脯氨酸类催化剂的载体类型和固载方法，催化剂载体类型主要包括离子液体、无机纳米粒子、有机聚合物以及新出现的聚合物离子液体和有机-无机杂化微球，固载方法主要包括硅烷化反应法、点击化学法以及可逆加成-断裂链转移（RAFT）聚合法，并对不同载体及固载方法的优缺点进行了总结。最后，针对目前固载化L-脯氨酸类催化剂存在的问题进行了原因分析并提出了改进建议，为以后新型固载化催化剂的研究开发提供了可能。     

Comparative study of poly(vinyl alcohol)‐based support materials for the immobilization of glucose oxidase

BACKGROUND: The performances of four types of glucose oxidase (GOD) immobilization materials based on poly(vinyl alcohol) (PVA) were compared. The matrices of interest were chemically‐linked PVA, freeze‐thawed PVA cryogel, tetramethoxysilane (TMOS) sol‐gel‐PVA hybrid material, and alumina sol‐gel‐PVA hybrid material. RESULTS: Overall, the membranes showed good sensitivity except for the chemically cross‐linked PVA. However, the main differences with the enzyme immobilization methods were enzyme leakage and values of K_m^app. CONCLUSION: Freeze‐thawed PVA‐GOD membranes and TMOS‐PVA, which showed satisfactory sensitivity and adequate value of K_m^app, were quite promising as support materials for immobilizing GOD. Copyright © 2007 Society of Chemical Industry     

Synthesis of alginate beads filled with nanohydroxyapatite: An efficient approach for fluoride sorption

Nanohydroxyapatite (n‐HAp) powder is a promising adsorbent material with high defluoridation capacity (DC); however, it causes pressure drop during field applications. To overcome such problems and utilize the advantages of n‐HAp, it is aimed to prepare n‐HAp in a usable bead form with the support of alginate (Alg) biopolymer. n‐HApAlgLa composite beads were synthesized by introducing n‐HAp powder in Alg polymeric gel, and the resulting solution was dropped into La³⁺ ions for crosslinking. Defluoridation experiments were carried out in batch mode to optimize various influencing parameters like contact time, pH, challenger anions, initial fluoride concentrations, and temperature. The beads were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy with energy‐dispersive X‐ray analyzer analysis. The sorption process was explained using diverse isotherms and kinetic models. The values of thermodynamic parameters indicate that the nature of fluoride is spontaneous and endothermic in nature. In field studies, n‐HApAlgLa beads reduce the fluoride concentration below the tolerance limit. The regeneration and reusability studies were proposed to effectively use the sorbent. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41937.     

Utilization of rice hull ash as a support material for immobilization of Candida cylindracea lipase

Rice hull ash was heated in a muffle furnace at 700°C for 2 h and metallic oxides were leached with 10% sulfuric acid. The acid-activated ash was then examined for immobilization of Candida cylindracea lipase. Immobilization was carried out by direct addition of the enzyme solution to the activated ash suspended in hexane. The immobilized lipase retained 30% of its hydrolytic activity, but thermal stability was greatly increased. Half-lives of the immobilized enzyme at 50, 60, and 70°C were 45, 17, and 4 min, respectively. Optimal pH of the immobilized enzyme was 7.2. The apparent K_m and V_max for olive oil were 41 mM and 99.5 μmol/h-mg solid, respectively.     

仿生合成氧化锆固定化漆酶处理孔雀石绿

以溶菌酶作为诱导剂,仿生合成了ZrO₂固定化漆酶纳米颗粒,其酶活回收率达59%,采用场发射扫描电子显微镜（FESEM）、能谱仪（EDS）、热重分析仪（TGA）等手段对ZrO₂纳米颗粒及ZrO₂固定化漆酶颗粒进行表征,结果表明漆酶可成功固定到ZrO₂颗粒中,同时还证明了溶菌酶既作为诱导剂催化ZrO₂的形成,又作为生物模板同酶一起包埋在ZrO₂颗粒中。固定化漆酶的最适pH为3,最适温度为70℃,相比于游离酶,其pH、温度稳定性都有明显提高;固定化漆酶纳米颗粒在4℃下储存30d,活性为初始酶活的95%,重复使用5次,固定化酶的残余酶活力仍有60%。此外,固定化漆酶在6h内对孔雀石绿染料的脱色率高达95%以上,通过紫外-可见吸收光谱分析（UV-vis）可知,固定化漆酶对孔雀石绿染料的处理是由吸附和降解联合作用引起的脱色。     

Liquid velocity in a high‐solids‐loading three‐phase external‐loop airlift reactor

BACKGROUND: Airlift reactors are of interest for many different processes, especially for three‐phase systems. In this study the behavior of a high‐loading three‐phase external‐loop airlift reactor was examined. In particular, the effect of parameters such as airflow rate (riser superficial gas velocities between 0.003 and 0.017 m s^?1), solids loading (up to 50%, v/v) on liquid circulation velocity in the air‐water‐alginate beads system as a crucial hydrodynamic parameter was studied. RESULTS: It was observed that increase of the airflow rate resulted in increase of the liquid velocity in the system. The same result but less pronounced was observed by introducing small amounts of solid particles up to 7.5% v/v. However, further introduction of solids caused decrease of the liquid velocity. Laminar regime for the liquid circulation was observed for low gas velocities. Minimum gas velocities for recirculation initiation in the reactor were determined for all solid loadings and linear dependence on the solid content was found. Gas holdups for the three‐phase system were larger than for the two‐phase system in all experiments. A simple model for predicting the liquid circulation velocity in the three‐phase system with high solid loading of low‐density particles was developed. This model is based on the viscosity of integrated medium (solid + liquid) which is a new aspect to analyze this phenomenon. CONCLUSIONS: The developed model shows very good agreement with the experimental results for all solid loadings. It also includes the influence of reactor geometry on the liquid circulation velocity thus enabling optimization. Copyright © 2012 Society of Chemical Industry     

A low,particle‐sized,nonporous support for enzyme immobilization: Uniform poly(glycidyl methacrylate) latex particles

The uniform and nonporous poly(glycidyl methacrylate) (poly(GMA)) latex particles, 1.7 μm in size, were first tried as a support in enzyme immobilization. For this purpose, α‐chymotrypsin (CT) was selected as the model enzyme. The low particle size and nonporous character of the selected support allowed to carry out the enzyme–subtrate interaction on a sufficiently large surface area (3.36 m²/g) and in the absence of intraparticular diffusion limitations. This property is particularly important when the immobilized CT is used for the substrates with high molecular weights (i.e., proteins). The latex particles were synthesized by dispersion polymerization of GMA. The reactive character of poly(GMA) allowed the direct attachment of primary amine groups onto the particles. Confocal laser scanning microscopy (CLSM) showed that primary amine groups were preferentially located on the particle's surface. Hence, the selected enzyme, CT was immobilized on the surface of nonporous particles via glutaraldehyde activation. For CT‐immobilized poly(GMA) particles, the maximum activity (r_m) and Michealis constant (K_m) were found to be 17.2 μmol/mg CT min and 121.6 μm, respectively. No significant loss was observed in the activity of immobilized CT, during the course of experiments. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 818–824, 2006     

新型多孔碳化硅催化剂载体的制备与应用

采用气固相合成的方法制备出比表面积可达260 m²·g^－1的多孔SiC颗粒。对制备温度、时间进行了考察。将多孔SiC负载Co催化剂用于费托合成反应发现,由于SiC的化学惰性较强,金属与载体间的相互作用较弱,有利于钴氧化物的还原,提高了催化剂活性。同时SiC热导性好,有利于反应热量的及时移出,可防止催化剂烧结。CO单程转化率超过60%,表现出良好的催化活性。制备出的多孔碳化硅通过XRD、SEM、低温氮气吸附、TPR等手段进行了表征。     

Synthesis and photoinitiation properties of a novel quaternary ammonium tetraphenylborate salt

Quaternary ammonium salts are photobase generators. Recently, we prepared a novel quaternary ammonium tetraphenylborate salt bearing a 6‐methoxynaphthoylmethyl group. The structure of the products was confirmed by elemental analysis and ¹H‐NMR. Thermogravimetry showed its good thermostability. UV spectra and fluorescence emission spectra of the samples were studied. A mass spectrometry method for the analysis of the tertiary amine and other fragments produced by photolysis was established. Photolysis was found to produce both tertiary amine and free radicals. Therefore, the products of photolysis not only could cause thermal curing of epoxide but also could initiate the free‐radical polymerization of acrylate or methyl acrylate monomer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 399–405, 2006     

A H2O2 biosensor based on immobilization of horseradish peroxidase in electropolymerized methylene green film on GCE

A novel H2O2 sensor is achieved by immobilizing horseradish peroxidase (HRP) in an electropolymerized methylene green (PMG) redox film. The electropolymerization of MG is carried out in a neutral phosphate buffer solution with 5×10–5m methylene green (MG) by using a two-step method. The polymer film only occurs on glassy carbon (electrodes and the reason for this is identified. The critical factor for the electropolymerization of MG lies in the preanodization on a glassy carbon) electrode, because a large amount of positive charges are accumulated and used to create the cation radicals form the polymer film. The formal potentials of PMG is pH dependent with a slope of 57mV per pH unit between pH6.0 and 8.0, which is close to the anticipated Nernstian value of 59mV for a two-electron, two-proton process. The PMG itself and the PMG on the H2O2 sensor show electrochemical behaviour with a linear plot of peak current against scan rate in the range 20 to 100mVs–1.     

一种绿色生物防晒剂在化妆品中的应用

利用基因工程等生物技术从大豆中提取出可以有效吸收紫外线的天然防晒剂,并添加到化妆品中,制备出一种全新的可以有效吸收阳光辐射中的全波段紫外线的防晒化妆品。