Ethanol production by alginate immobilised yeast in a fluidised bed bioreactor

Yeast, immobilised in alginate beads of known standard size and mechanical strength, has been utilised in a novel design of fluidised bed bioreactor which avoids problems of particle flotation and gas logging. Circulating substrate simultaneously entered the top and bottom of the bed. The bioreactor operated reliably for periods of up to 20 days. Increasing alginate concentration in the range 1–5% (w/w) had little effect on the performance of the immobilised yeast in converting ethanol to glucose but reduced the tendency of beads to split. Increasing bead diameter in the range 1–5 mm increased the tendency to split and reduced overall conversion of glucose. A model was developed to describe the consumption of glucose within beads based on Michaelis–Menten kinetics and the diffusion of glucose into beads. Application of the model to experimental results showed maximum reaction velocity to be independent of bead diameter and alginate concentration. The model confirmed that the observed reduction in ethanol yield compared with free yeast cells was caused by the lower substrate concentration towards the centre of the bead as opposed to any change in the metabolic rate of the immobilised cells.     

Optimization of lactic acid production from whey by L casei NRRL B‐441 immobilized in chitosan stabilized Ca‐alginate beads

The production of lactic acid from whey by Lactobacillus casei NRRL B‐441 immobilized in chitosan‐stabilized Ca‐alginate beads was investigated. Higher lactic acid production and lower cell leakage were observed with alginate–chitosan beads compared with Ca‐alginate beads. The highest lactic acid concentration (131.2 g dm^?3) was obtained with cells entrapped in 1.3–1.7 mm alginate–chitosan beads prepared from 2% (w/v) Na‐alginate. The gel beads produced lactic acid for five consecutive batch fermentations without marked activity loss and deformation. Response surface methodology was used to investigate the effects of three fermentation parameters (initial sugar, yeast extract and calcium carbonate concentrations) on the concentration of lactic acid. Results of the statistical analysis showed that the fit of the model was good in all cases. Initial sugar, yeast extract and calcium carbonate concentrations had a strong linear effect on lactic acid production. The maximum lactic acid concentration of 136.3 g dm^?3 was obtained at the optimum concentrations of process variables (initial sugar 147.35 g dm^?3, yeast extract 28.81 g dm^?3, CaCO₃ 97.55 g dm^?3). These values were obtained by fitting of the experimental data to the model equation. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in lactic acid production using alginate–chitosan‐immobilized cells. Copyright © 2005 Society of Chemical Industry     

Modelling of phenol biodegradation by Candida tropicalis immobilised in alginate gel beads

Phenol‐degrading yeast Candida tropicalis were immobilised in alginate gel beads and photographed by scanning electron microscopy. Batch phenol biodegradation experiments were done in shaking flasks under varying conditions such as initial phenol concentrations and bead loadings. A mathematical model was proposed to simulate the batch phenol biodegradation process in the immobilised system, which took into account the internal and external mass transfer resistances of phenol and oxygen and the double‐substrate phenol–oxygen intrinsic kinetics. The validation of this model was done by the comparison between the model simulations and the experimental measurements of phenol concentration profiles in the main liquid phase. Moreover, the time and radius courses of phenol, oxygen, and cell concentration profiles within the alginate gel beads were reasonably predicted by the proposed model.     

Utilisation of immobilised activated sludge for the biosorption of chromium (VI)

The objective of this investigation was to study the biosorption of Cr (VI) on immobilised activated sludge (IAS) and calcium alginate (CA) using batch system. The optimal pH for Cr (VI) biosorption by IAS and CA was 2.0 and 4.0, respectively. Equilibrium was attained at approximately 120 min for both biosorbents. For both biosorbents, the equilibrium biosorption capacity (mg/g) increased as the initial metal ion concentration increased and the concentration of biosorbent decreased. The rate of biosorption onto IAS and pure CA (as mg/g) increased from 5.02 to 87.66 and 4.97 to 79.09 as the concentration of Cr (VI) ions increased from 10 to 1000 mg/L, respectively. In the case of biosorbent concentration, as the concentration of IAS and pure CA increased from 1 to 20 g/L, the equilibrium uptake (q_e) decreased from 21.33 to 1.57 and 19.41 to 1.38 mg/g, respectively. The biosorption data showed that the Langmuir model was more suitable than the Freundlich model. Also, the results indicated that the pseudo‐second order model was the most suitable for Cr (VI) biosorption onto IAS and CA. © 2011 Canadian Society for Chemical Engineering     

Characterization of the structure and diffusion behavior of calcium alginate gel beads

A simple and novel method using gel shrinkage to indirectly characterize the structure of calcium alginate gel (CAG) beads during the calcium alginate gelation process was presented in this study. The effect of preparation process parameters (gelling cations, bead diameter, and alginate M _w and concentration) on the structure of the CAG bead formation process was thoroughly investigated. It was found that (a) the concentration of the Na⁺ and Ca²⁺ ion in gel bath was found to be the determining factor in the gel structure formation process by regulating the dissociation of alginate and the complexation of the calcium; (b) Na⁺ acts as a competitor with calcium and a screen in the electrostatic repulsion; (c) the effect of beads size below 700 μm on the structure of CAG beads can be neglected; and (d) the sodium alginate concentration has no significant effect on the gel formation process. Furthermore, the diffusion of bovine serum albumin (BSA) was controlled by the density of CAG bead. Consequently, a faster diffusion rate of BSA within the looser structure of beads can be observed. These results are keys to understanding the behavior and performance of beads in their utilization medium. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48923.     

海藻酸钙固定化零价铁抗团聚及堵塞的作用机制

以海藻酸钠(SA)、氯化钙、微米零价铁(MZVI)为原料,制备了海藻酸钙(CA)固定化MZVI填料(CAZ),通过静态烧杯实验和动态PRB模型实验,探讨了CA运用对Cr(Ⅵ)的去除性能的影响,并通过电镜扫描分析了CA避免团聚、堵塞机制。实验结果表明,CA凝胶颗粒的运用能显著提升MZVI的除Cr(Ⅵ)性能,CAZ相比MZVI对Cr(Ⅵ)的去除率和反应速率分别提升7.1倍、23.0倍;MZVI利用率的提高是CAZ反应器处理Cr(Ⅵ)水量显著大于MZVI反应器的主要原因,MZVI反应速率的提高是CAZ反应器出水Cr(Ⅵ)浓度显著低于MZVI反应器的主要原因。电镜扫描结果表明,SA与氯化钙交联形成的CA具有丰富的骨架孔道结构,具有骨架支撑作用,能有效克服MZVI颗粒因重力作用导致团聚、降低比表面积的缺陷。CA表层固定的MZVI颗粒与Cr(Ⅵ)反应生成的(Fe_xCr_1-x)(OH)₃络合沉淀会冲破CA表层外壳,释放到零价铁-渗透反应墙(Fe⁰-PRB)系统中,导致PRB反应初期出现堵塞现象;大部分MZVI颗粒...     

Properties of cathepsin B immobilized in calcium alginate beads

Cathepsin B (EC 3.4.22.1), purified from goat brain, was immobilized in calcium alginate beads in the presence of bovine serum albumin. The immobilized enzyme retained ∼63% of the original activity and could be used for seven successive batch reactions with retention of 22–30% of the initial activity. Immobilized cathepsin B hydrolysed α-N-benzoyl-D ,L -arginine-β-naphthylamide (BANA) maximally at pH 5·5, exhibiting a shift of 0·5 pH unit from that of the soluble enzyme (pH optima 6·0). It showed enhanced stability in acidic as well as alkaline environments in comparison to the free enzyme. The optimal temperature and thermal stability were not altered significantly after immobilization. The K_m value for the immobilized enzyme was two-fold higher than for the soluble enzyme.     

Detoxification of cyanide by immobilised fungi

Cyanide detoxification was studied by immobilisation of fungal mycelia that had been induced to form cyanide hydratase (formamide hydrolyase) which is able to hydrolyse cyanide to formamide. The fungal pathogens of cyanogenic plants, Stemphylium loti, Gloeocercospora sorghi and Fusarium moniliforme were immobilised using polyelectrolyte flocculating agents. The effect of immobilisation on the enzymic properties of S. loti and G. sorghi were investigated. The apparent K_m values increased from 21.0 mmol and 25.5 mmol KCN to 43.5 mmol and 71.0 mmol KCN, respectively. The pH profile for the two enzymes widened on immobilisation. The stoichiometry of 1:1 cyanide utilisation to formamide formation was retained on immobilisation, with complete conversion of 70 mmol KCN in 120 min by 0.12 g dry wt of S. loti and in 6 min by 0.13 g dry wt of G. sorghi. When the two fungi were stabilised by immobilisation, and tested in column reactors containing 1.2 g dry wt of S. loti and 1.3 g dry wt of G. sorghi, they completely converted cyanide (70 mmol; added continuously at 7.5 ml h^?1) into formamide for 2 days and 30 days, respectively. Stability was enhanced by inclusion of 1.0 mmol glucose in the 70 mmol KCN solution, by a further 10 h for S. loti and an extra 10 days for G. sorghi. Operational stabilities of immobilised G. sorghi (1.3 g dry wt) and F. moniliforme (1.0 g wet wt) in column reactors, with 100 % cyanide conversion, at varying flow rates was investigated. G. sorghi was stable for 15, 10 and 2 days whereas F. moniliforme was only stable for 48, 20 and 10 h at 30, 60 and 120 ml h^?1 flow rates respectively.     

海藻酸钙纤维生产设备的研制

结合800 t/a海藻酸钙纤维生产设备的一些基本工艺参数,对湿法纺丝机和湿热牵伸机两种海藻酸钙纤维生产设备的研制进行了探讨。指出任何一种设备的结构都不是一成不变的,它与整条生产线的纺丝位数、工艺条件等有着直接的关系;为适应多机位纺丝,推荐双凝固浴槽式湿法纺丝机。     

Regeneration of NADH in a bioreactor using yeast cells immobilised in alginate fibre. II: Detailed results

Saccharomyces cerevisiae cells were immobilised in calcium alginate fibres and used in a reactor as a source of alcohol dehydrogenase for the NAD⁺ to NADH reaction. Kinetic parameters were established for both the free enzyme and the fibre reactor. Detailed calculations for the free enzyme studies established the superiority of the Elmore–Kingston–Shields computer calculation of the initial rates. There was little difference between the Cornish-Bowden and the Hanes methods for subsequent generation of the kinetic parameters. Initial reaction rates that were obtained for the free enzyme gave kinetic parameters which were 65–80% below those obtained in the bioreactor. It is apparent that the diffusion limited the rate of reaction in the immobilised system. The bioreactor operated at high conversions at relatively low inlet concentrations of substrates. As the substrate concentration was raised the percentage conversion fell even though the amount of product produced overall rose substantially.     

丙烯腈接枝改性海藻酸钙水凝胶中水杨酸的释放行为

将海藻酸钙水凝胶与丙烯腈单体进行不同程度的接枝共聚改性,再由FTIR加以分析,并测定包埋了水杨酸模拟药物的改性海藻酸钙水凝胶在不同介质中的药物释放量。实验表明,改性海藻酸钙水凝胶的药物释放量既与介质有关,也取决于接枝率的大小。     

Intraparticle cell growth and cell leakage in cultures of Nicotiana tabacum cells immobilized in calcium alginate gel beads

Immobilized Nicotiona tabacum cells in calcium alginate gel beads were prepared under various conditions and then were cultivated. The effects of different conditions of preparation, in relation to concentration of calcium ions (Ca²⁺), on intraparticle cell growth and cell leakage from beads were investigated experimentally. As the amount of Ca²⁺ incorporated into the beads increased, the numbers of cells leaked from the beads into the medium decreased. However, cell growth was inhibited by high Ca²⁺ concentrations in the beads. Optimal conditions existed, which prevented cell leakage without inhibiting intraparticle cell growth. The effect of adding CaCl₂ to the culture medium was also studied. The Ca²⁺, used for the alginate crosslinking, gradually leached from the beads with increasing cultivation time, such that the beads gradually became brittle and fragile. The addition of CaCl₂ was effective in preventing Ca²⁺ loss from the beads and cell leakage. © 2000 Society of Chemical Industry     

高压静电法制备单分散性的海藻酸钙微胶珠

In this paper, the effect of operation parameters on the monodispersity of calcium-alginate gel beads prepared in high-voltage electrostatic field were analyzed. The parameters included the applied potential （U）, the distribution of electrostatic field, the frequency and the flow rate of solution through the capillary. Furthermore, the process is analyzed with the theory of jet break-up in electrostatic field. The result showed that the modified symmetrical electrostatic field was more advantageous in preparing the monodispersed gel beads than the traditional method. Meanwhile, gel beads with good monodispersity （CV〈20%） and stability without aggregation were produced under a range of applied potential （U）, frequency and flow rate of solution through the capillary.     

海藻酸凝胶性质对蛋白质扩散的影响

通过观察冷冻干燥海藻酸凝胶的断面扫描电镜(SEM)照片与卵清蛋白从海藻酸凝胶中的释放试验,分析了海藻酸凝胶性质对蛋白质在凝胶中扩散的影响。凝胶的SEM照片可见,海藻酸钙的冷冻干燥颗粒内为较大的圆孔,海藻酸锌凝胶内为较小的长孔,表明海藻酸锌高分子链在凝胶颗粒中的体积分率相对较大同时刚性较强;卵清蛋白从海藻酸凝胶颗粒中释放的试验结果表明,由于上述海藻酸锌凝胶的特性,导致海藻酸锌对卵清蛋白扩散阻滞作用相对较强;根据试验数据计算得卵清蛋白在海藻酸钙、海藻酸锌凝胶颗粒中的扩散系数分别为1.19×10-7、0.07×10-7cm2/s,利用阻滞模型计算得海藻酸锌高分子链在凝胶颗粒中体积分率约为海藻酸钙高分子链在凝胶颗粒中体积分率的1.7倍。     

多通道微胶囊制备系统规模化制备海藻酸钙微胶珠

利用自制多通道强制电场微胶囊制备系统制备海藻酸钙微胶珠,分析了微胶囊制备系统中电极电场分布规律,考察了进料气压、脉冲电压、脉冲频率、脉冲宽度、辅助电压等系统调节参数对微胶珠制备过程的影响,发现制备过程中微胶珠粒径大小与产率主要由进料气压决定,而微胶珠的分散性则是由多个因素共同作用的结果。通过优化条件制备的微胶珠分散系数较小（CV<20%）,球形度良好,表面光洁,并且产率是传统静电法的20~40倍,使海藻酸钙微胶珠大规模制备成为可能。     

Blend membranes from carboxymethylated chitosan/alginate in aqueous solution

The blend membranes were satisfactorily prepared by coagulating a mixture of O‐carboxymethylated chitosan (CM‐chitosan) and alginate in aqueous solution with 5 wt % CaCl₂, and then by treating with 1 wt % HCl aqueous solution. Their structure and miscibility were characterized by scanning electron micrograph, X‐ray diffraction, infrared spectra, differential thermal analysis, and atomic absorption spectrophotometer. The results indicated that the blends were miscible, when the weight ratio of CM‐chitosan to alginate was in the range from 1 : 1 to 1 : 5. The polymers interpenetration including a Ca²⁺ crosslinked bridge occurred in the blend membrane, and leads to high separation factor for pervaporation separation of alcohol/water and low permeation. The tensile strength in the wet state (σ_b = 192 kg cm⁻² for CM‐chitosan/alginate 1 : 1) and thermostability of the blend membranes were significantly superior to that of alginic acid membrane, and cellulose/alginate blend membranes, owing to a strong electrostatic interaction caused by —NH₂ groups of CM‐chitosan with —COOH groups of algic acid. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 610–616, 2000     

饲用碘酸钙/海藻酸钠凝胶微球及其稳定性

为隔绝饲用碘酸钙在贮存、使用过程中与还原性物质，如维生素c (VC)的反应。以碘酸钙(Ca(IO3)2)为芯材，海藻酸钠(SA)为壁材，纳米碳酸钙(Nano-CaCO3)为交联钙源，采用改良的内源乳化法制备了碘酸钙/海藻酸钠凝胶微球(Ca(IO3)2/SAMS)。利用FTIR、SEM、TG、XRD对Ca(IO3)2/SAMS进行了表征，同时测定了其在VC溶液中的稳定性，探讨了Ca(IO3)2/SAMS形成机制。结果表明，Ca(IO3)2/SAMS呈球形，粒径约为20~40 μm，其表面有大量碘酸钙晶体。Ca(IO3)2和Ca(IO3)2/SAMS在VC溶液中VC分解50%用时(t50%)分别为54.8 min和78.3 min，Ca(IO3)2在饲料中的稳定性得到明显提升。     

Immobilization of hybridoma cells in chitosan alginate beads

A new method for immobilizing hybridoma cells using chitosan-stabilized calcium alginate beads was developed. The ionotropic gelation of chitosan and calcium with alginate resulted in the formation of highly cross-linked, porous beads that were mechanically and chemically stable in phosphate buffered medium. Hybridomas entrapped in these beads were cultured semi-continuously using periodic medium exchange. Viable population densities in the order of 5 × I0⁷ cells/mL were attained within the beads and up to two-fold increases in volumetric monoclonal antibody (MAb) productivity over batch suspension cultures were observed. Oxygen mass transfer limitations within the chitosan-alginate beads were evaluated by considering biokinetics and diffusive transport. Model equations were developed and used to evaluate the effect of bead diameter on the contained cells. The predictions were consistent with experimental observations of maximum viable population densities attained in beads of various size.     

变色圈法筛选高产氨基酰化酶米曲霉菌株

将变色圈法用于筛选高产氨基酰化酶的米曲霉菌株,减少了筛选过程的工作量、缩短了筛选周期。通过实验验证了该方法在筛选高产氨基酰化酶米曲霉菌株时的可行性,并将其用于筛选经紫外线和硫酸二乙酯复合诱变的米曲霉。从突变株中获得了一株高产氨基酰化酶菌株W53,对其生长特性和产酶特性进行了研究。结果表明,米曲霉的氨基酰化酶是生长偶联型,菌体生物量和氨基酰化酶活力同时达到最高;突变株W53和出发菌株W19的产酶过程基本一致;W53拆分N-乙酰-DL-蛋氨酸的酶活力最高可达2569 U/g,比出发菌株W19提高了14.9%。     

海藻酸钙纤维的结构与性能

研究了自制的海藻酸钙纤维的结构、热性能、燃烧性能以及对酸、碱和盐溶液的化学稳定性能。结果表明:海藻酸钙纤维的微观形态和粘胶纤维的相似,红外光谱结果证实了海藻酸钙纤维中"egg-box"结构的存在;海藻酸钙纤维的化学稳定性较差,随着处理液浓度和温度的升高,以及处理时间的延长,其稳定性越差;海藻酸钙纤维的热稳定性较好,极限氧指数为34.4,具有很好的阻燃性,属于难燃纤维。