生物分离中应用超滤的若干问题

本文对超滤技术应用中普遍存在着的诸多重要因素进行了讨论,有些内容在一般教材和文献中较少详细论述。本文从应用者角度分析了产率、吸附、消毒和保存、温控、活性问题、压力和透过速率以及技术联用应该注意的问题,并将其与膜质量参数、膜配置选择和操作模式相关联。对活性生物样品的处理,文中给予了较多的讨论,并希望结合超滤技术自身特点,在选择和配置一节中,对系统的各组成部分进行配置优化。应用中,安全性操作也贯彻于各个问题的讨论之内。在最后,涉及超滤法进行分子量分级的问题,提出了参数上的建议 。     

生物分离中应用超滤的若干问题

本文对超滤技术应用中普遍存在着的诸多重要因素进行了讨论。有些内容在一般教材和方面中较少详细论述。本文从应用者角度分析了产率、吸附、消毒和保存、温控、活性问题、压力和秀过速率以及技术联用应该注意的问题,并将共与膜质量参数、膜配置选择和操作模式相关联。对活性生物样品的处理,文中给予了较多的讨论,并希望结合超滤技术自身特点,在选择和配置一节中,对系统的各组成部分进行部分进行配置优化。应用中,安全性操作也     

超滤法浓缩提取大蒜SOD机制的研究

本文研究了超滤法浓缩提取大蒜SOD过程中不同膜材料、压力差、循环速度、扩散系数和截留率对透过通量的影响和关系,求得了各种膜的传质系数k和真实截留率R0以及PS膜的透过通量与压力差的关系式限通量最后探讨了超滤过程中分子形变对酶失活率的影响,并建立了酶失活率T与分子半径r二者关系式     

基于红芪芒柄花素保留率建立纤维性根茎药材超滤预测模型

以膜孔径、操作压力、滤过温度为输入变量,以红芪酶解提取液在不同超滤条件下的芒柄花素保留率为输出变量,采用L-M算法优化网络参数,建立适用于纤维性根茎药材超滤的芒柄花素保留率BP神经网络预测模型,并对模型的预测性能和适用性及最优工艺条件和各条件对芒柄花素保留率的影响进行考察。该模型对红芪和黄芪酶解提取液超滤后的芒柄花素保留率预测的平均误差率分别为1.78%和1.92%。最优超滤工艺条件为:膜孔径100 nm,操作压力0.15 Mpa,滤过温度45℃。各条件对芒柄花素保留率的影响大小为:滤过温度膜孔径操作压力。结果表明,所建神经网络预测精度较高,适用性较好,具有很好的实用价值,可避免对成分相近纤维性根茎药材的超滤工艺重复优化的问题。     

超滤法提纯万古霉素的应用

采用Ultra-flo超滤系统提纯未经任何预处理的万古霉素发酵液。结果表明:万古霉素收率由传统工艺(板框加压过滤)的87%提高到94%,滤液的透光度比传统工艺提高了25%;系统平均膜通量可达120L/(m2.h);被污染的膜经清洗后与新膜没有明显差异;合理加水量为投料量的2.5倍。Ultra-flo超滤系统完全能代替传统工艺。     

大豆乳清中蛋白质和异黄酮的超滤分离技术

研究了用超滤技术分离大豆乳清中的蛋白质和异黄酮的工艺条件. 结果表明,大豆乳清在超滤之前要进行预处理以减轻膜污染;通过2因素3水平正交试验,确定了最佳的预处理工艺：按大豆乳清中固形物含量的5%,向其中加入CaCl₂,并在85 ℃下加热15 min,在此条件下,蛋白质的沉淀率为49.8%,异黄酮的保留率为90.4%;通过单因素试验,确定了比较合适的超滤条件：选择切割分子量（MWCO）为10000的聚醚砜膜,超滤压力选择51～68 kPa,超滤温度选择30 ℃～40 ℃.在此条件下,大豆乳清中蛋白质的截留率为83.9%,而异黄酮的截留率为7.6%.     

具有ACE抑制活性的霞水母酶解肽制备条件优化

目的:采用胰蛋白酶制备霞水母ACE抑制肽,并以响应面法优化酶解肽制备工艺,通过超滤分离获得具有ACE抑制作用的酶解肽活性部位。方法:单因素实验以ACE抑制率为指标,考察温度、酶解时间、pH、加酶量,进一步通过响应面法优化酶解工艺,以不同截留分子量的纤维膜进行分离。结果:胰蛋白酶水解霞水母制备ACE抑制肽的最佳工艺条件为:酶解温度:49.6℃,加酶量为0.69%,pH为7.8,酶解时间2.0h,酶解产物的平均ACE抑制率为56.79%,与预测值57.20%的相对误差为0.41%,经过超滤分离获得分子量1k Da的酶解产物,ACE抑制活性最高,其IC50为66.58μg/ml。结论:确定霞水母酶解肽的制备工艺,其中分子量1kDa的部分为主要效应物质基础。     

人工膜肺氧合器临床应用研究及发展趋势

本文综述目前我国膜式氧合器临床应用,人工膜肺领域的研究成果和发展趋势。通过问卷调查形式显示我国近年CPB （Cardiopulmonary Bypass,体外循环）技术发展迅速,膜式氧合器应用量逐年升高,应用ECMO（extracorporeal membrane oxygenation, 体外膜肺氧合）辅助循环的比例显著增加。人工膜肺多方面研究进展包括：为新生儿体外循环设计的婴幼儿膜式氧合器,整合 动脉滤过器与超滤设备的小型化氧合器,这些设计可以明显减少体外循环回路整体表面积和预充量,避免CPB 中过度血液稀释, 降低或不用输入红细胞。同时减轻由于血液与人工材料接触诱发的炎性反应。人工膜肺在人工材料改进和结构设计有很显著发 展,通过改进气体交换的人工膜材料,优化结构设计,提高血液抗凝能力和耐受力,设计出如ECMO 可以长时间应用于辅助循环 来延续和支持病人的生命。对膜式氧合器的试验研究的相关进展和展望也会在本文讨论。     

酶的超滤浓缩装置

常用的“沉淀法”和“去除溶剂法(solvent remo-val)”浓缩酶蛋白,由于有“相态”的变化而容易使酶变性,对于大体积酶溶液的浓缩也较困难。用各向异性膜加压超滤法(简称超滤法),在其可筛分的范围内可进行分离并且没有“相态”的变化,这样可避免酶的变性,还可在较短时间内进行大体积稀溶液的浓缩。超滤法还具有设备简单、经济和操作方便等特点。超滤的应用范围很广,可用于蛋白质、核酸和酶的脱盐、大     

超滤膜分离纯化珊瑚藻溴过氧化物酶

利用超滤膜对珊瑚藻中溴过氧化物酶(EC 1.11.1.18,分子质量740kDa)进行分离纯化,对膜的截留分子质量、操作压力、起始蛋白质浓度、搅拌速率、pH、离子强度等条件进行了优化。超滤分离纯化最优条件为:截留分子质量为100kDa的聚偏氟乙烯(PVDF)膜,操作压力为0.02MPa,搅拌速率为600r/min,起始蛋白质浓度为0.1g/L,pH=6.0。对粗酶液先进行热沉淀纯化,再进行超滤纯化,溴过氧化物酶被纯化了21倍,比活为212U/mg,酶活回收率为96%。     

Effluent recirculation to improve perchlorate reduction in a fixed biofilm reactor

The effect of effluent recirculation on perchlorate reduction in a nominally plug-flow fixed biofilm reactor was studied in two cases: influent concentrations of 10 and 400 microg/L at low hydraulic loading rates (1.9 and 37.5 m(3)/m(2)/day without and with recirculation, respectively) and after a step increase in perchlorate concentration to 1,000 microg/L at the higher hydraulic loading rate (5 and 100 m(3)/m(2)/day without and with recirculation, respectively). Complete perchlorate reduction was sustained for influent concentrations of 400 and 10 microg/L in both flow regimes at the lower hydraulic loading rates. Reactor tracer profiles showed that biofilm diffusion had a more significant effect on mass transfer in the plug flow reactor compared with recirculation. The recirculation bioreactor acclimated more rapidly to increased hydraulic and perchlorate mass loading rates with significantly lower effluent perchlorate compared to the plug flow reactor: 16 microg/L versus 46 microg/L, respectively, although complete perchlorate removal was not achieved in either flow regime after 21 days acclimation to the higher loading. Total biofilm mass was more uniformly distributed in the recirculation reactor which may have contributed to better performance under increased perchlorate loading.     

Stable hybridoma cultivation in a pilot-scale acoustic perfusion system: long-term process performance and effect of recirculation rate

Perfusion systems have the possibility to be operated continuously for several months. It is important that the performance of the cell retention device does not limit the operation time of a perfusion process used in the production of active pharmaceutical ingredients. Therefore, the aim of this study was to investigate the reliability and long-term stability of an acoustic perfusion process using the 200 L/d BioSep. As the BioSep is an external device, it is possible that dependent on the recirculation rate nutrient gradients occur in the external loop, which could affect the cell metabolism. Therefore, the effect of possible nutrient gradients on cell metabolism, viability and productivity was studied by varying the recirculation rate. In this study, it is shown that a perfusion process using a pilot-scale acoustic cell-retention device (200 L/d) is reliable and simple to operate, resulting in a stable 75-day cultivation of a hybridoma cell line producing a monoclonal antibody. The recirculation rate had a significant effect on the oxygen concentration in the external loop, with oxygen being depleted within the cell-retention device at recirculation rates below 6 m3/m(reactor)3.d (=600 L/d). The oxygen depletion at low circulation rates correlated with a slightly increased lactate production rate. For all other parameters no effect of the recirculation rate was observed, including cell death measured through the release of lactate dehydrogenase and specific productivity. A maximum specific productivity of 12 pg/cell.d was reached.     

Patterns of routine swimming and metabolic rate in juvenile cyyprinids at three temperatures: analysis with a respirometer-activity-monitoring system

Summary The spontaneous swimming activity and oxygen consumption of juvenile roach (Rutilus rutilus (L.)), were monitored for 48–72 h at 8, 15 and 20°C and a photoperiod (L:D) of 11:13. At low levels of activity metabolic cost is constant and thus corresponds to the standard rate of metabolism (low cost activity). At higher levels of activity metabolic cost increases in proportion with the degree of activity. The slope for this high cost activity indicates an expenditure of 0.4–1.3 mol O₂·g^-1·h^-1 per arbitrary activity unit at the three experimental temperatures. Extrapolation of this relationship to zero activity would underestimate the measured standard metabolic rate. High cost activity occurred in only one experiment out of three at 8°C, low cost activity hardly at all at 20°C, whereas at 15°C both forms of activity were present in five of the seven experiments conducted. Thus, not only the intensity but also the pattern of activity is affected by environmental temperature.     

Separation of lactic acid-producing bacteria from fermentation broth using a ceramic microfiltration membrane with constant permeate flow

The influence of several operating parameters on the critical flux in the separation of lactic acid-producing bacteria from fermentation broth was studied using a ceramic microfiltration membrane equipped with a permeate pump. The operating parameters studied were crossflow velocity over the membrane, bacterial cell concentration, protein concentration, and pH. The influence of the isoelectric point (IEP) of the membrane was also investigated. In the interval studied (5.3-10.8 m/s), the crossflow velocity had a marked effect on the critical flux. When the crossflow velocity was increased the critical flux also increased. The bacterial cells were retained by the membrane and the concentration of bacterial cells did not affect the critical flux in the interval studied (1.1-3.1 g/L). The critical flux decreased when the protein concentration was increased. It was found that the protein was adsorbed on the membrane surface and protein retention occurred even though the conditions were such that no filter cake was present on the membrane surface. When the pH of the medium was lowered from 6 to 5 (and then further to 4) the critical flux decreased from 76 L/m(2)h to zero at both pH 5 and pH 4. This was found to be due to the fact that the lowering in pH had affected the physiology of the bacterial cells so that the bacteria tended to adhere to the membrane and to each other. The critical flux, for wheat flour hydrolysate without particles, was much lower (28 L/m(2)h) when using a membrane with an IEP of 5.5 than the critical flux of a membrane with an IEP at pH 7 (96 L/m(2)h). This was found to be due to an increased affinity of the bacteria for the membrane with the lower IEP.     

Effect of sparger design on hydrodynamics of a gas recirculation anaerobic bioreactor

The effects of sparger design and gas flow rate on, gas holdup distribution and liquid (slurry) recirculation velocity have been studied in a surrogate anaerobic bioreactor used for treating bovine waste with a conical bottom mixed by gas recirculation. A single orifice sparger (SOS) and a multi-orifice ring sparger (MORS) with the same orifice open area and gas flow rates (hence the same process power input) are compared in this study. The advanced non-invasive techniques of computer automated tomography (CT) and computer automated radioactive particle tracking (CARPT) were employed to determine gas holdup, liquid recirculation velocity, and the poorly mixed zones. Gas flows (Q(g)) ranging of 0.017 x 10(-3) m(3)/s to 0.083 x 10(-3) m(3)/s were used which correspond to draft tube superficial gas velocities ranging from 1.46 x 10(-2) m/s to 7.35 x 10(-2) m/s (based on draft tube diameter). Air was used for the gas, as the molecular weights of air and biogas (consisting mainly of CH(4) and CO(2)) are in the same range (biogas: 28.32-26.08 kg/kmol and air: 28.58 kg/kmol). When compared to the SOS for a given gas flow rate, the MORS gave better gas holdup distribution in the draft tube, enhanced the liquid (slurry) recirculation, and reduced the fraction of the poorly mixed zones. The improved gas holdup distribution in the draft tube was found to have increased the overall liquid velocity. Hence, for the same process power input the MORS system performed better by enhancing the liquid recirculation and reducing the poorly mixed zones.     

Separation of proteases from yellowfin tuna spleen by ultrafiltration

Separation of protease, trypsin and chymotrypsin from yellowfin tuna spleen extract by ultrafiltration (UF) using regenerated cellulose membranes with molecular weight cut off (MWCO) 30 and 100 kDa was studied. The 100 kDa membrane had a higher transmission of enzymes than that of the 30 kDa membrane. The enzyme transmission varied from 0.01 to 0.18 and from 0.6 to 0.8 for the 30 kDa membrane and 100 kDa membrane, respectively. The protein transmission was about 0.8 for both membranes. Increasing cross-flow rate and transmembrane pressure (TMP) increased permeate flux. The limiting fluxes at cross-flow rate 120, 240 and 360 L/h for the 30 kDa membrane were 17.3, 43.9 and 54.7 L/m2h, respectively and the limiting fluxes at the same flow rate for 100 kDa membrane were 34.1, 51.1 and 68.4 L/m2h, respectively. The separation of these proteases was achieved using the 30 kDa membrane. The purities of proteases were increased more than ten times at TMP 1.5 bar and cross-flow rate 360 L/h by diafiltration using 30 kDa membrane.     

Cadmium removal in a biosorption column

New biosorbent material derived from a ubiquitous brown marine alga Ascophyllum nodosum has been examined in packed-bed flow-through sorption columns. It effectively removed 10 mg/L of cadmium down to 1.5 ppb levels in the effluent, representing 99.985% removal. The experimental methodology used was based on the early Bohart and Adams sorption model, resulting in quantitative determination of the characteristic process parameters which can be used for performance comparison and process design. An average metal loading of the biosorbent (N(0)) determined was 30 mg Cd/g, corresponding closely to that observed for the batch equilibrium metal concentration of 10 mg Cd/L. The critical bed depth (D(min)) for the potable water effluent quality standard (0.005 mgg Cd/L) varied with the column feed flow rate (2.4 to 9.6 L/h . cm(2)) from 20 to 50 cm. The sorption column mass transfer and dispersion coefficients were determined, which are also required for solving the sorption model equations. (c) 1994 John Wiley & Sons, Inc.     

Hydrogenotrophic denitrification of synthetic aquaculture wastewater using membrane bioreactor

A hydrogenotrophic denitrification system was evaluated in removing nitrate from synthetic aquaculture wastewater for recirculation purposes. Two membrane bioreactor (MBR) systems, namely, aeration–denitrification system (ADS) and denitrification–aeration system (DAS) were studied with 50 mg/L of influent concentrations for both organic matter and nitrate nitrogen. The DAS achieved better removal efficiency of 91.4% total nitrogen (T-N) and denitrification rate of 363.7 mg/L.day at a HRT of 3 h compared to ADS. Further, there was no nitrite accumulation in the DAS effluent. The nitrite accumulation in ADS effluent was lesser when CO₂ was used as buffer rather than K₂HPO₄ and KH₂PO₄. Estimation of kinetic parameters of hydrogenotrophic bacteria indicated lesser sludge production compared to heterotrophic denitrification. In the DAS, membrane fouling was nonexistent in the aeration reactor that was used to produce the recirculating effluent. On the contrary, membrane fouling was observed in the denitrification reactor that supplied hydrogen to the mixed liquor. Thus, this study demonstrated DAS capability in maintaining the acceptable water quality appropriate for aquaculture, in which a closed recirculating system is typically used.     

Vibrating membrane filtration for recovery and concentration of insect killing nematodes

New experimental data are reported that demonstrate the use of a novel vibrating membrane filter (VMF) for the combined recovery and concentration of two species of nematodes, S. feltiae and P. hermaphrodita, from mature liquid fermentation cultures. The disk membrane module had a working surface area of 0.2 m(2) and was operated at a constant flow rate of 0.2 m(3) h(-1). The recovery of the viable nematodes from the spent media and nonviable nematodes was assisted by an independently imposed oscillatory motion of the disk assembly, which produced an intense shear field at the membrane surface with calculated mean values on the order of 10(4) s(-1). Adult (nonviable) nematodes in the fermentation culture were preferentially dissolved in a detergent (sodium dodecylsulfate) and successfully separated from the juveniles using the VMF equipment. Permeate fluxes on the order of 15 to 30 L/m(2/)h were achieved for an operating transmembrane pressure of 800 mbar. Industrial-scale liquid fermentation for the manufacture of nematodes as biopesticides produces the viable nematode life stages in low-concentration suspension containing large quantities of spent media and other waste material. The VMF equipment provided a flexible operation for separation, cleaning, and concentration of viable nematodes from the fermentation broths.