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%。     

溶液中木质素和葡萄糖的超滤分离

以木质素和葡萄糖的混合溶液为木质纤维素水解液模型,采用截留相对分子质量为5 000的卷式聚醚砜膜对葡萄糖和木质素进行全回流模式的分离,探讨了木质素和葡萄糖浓度、操作压力、错流速率对通量、木质素和葡萄糖截留率的影响。结果表明:在实验条件范围内,通量随葡萄糖浓度和木质素浓度的增加而降低,并随操作压力、错流速率的增加而增加。木质素截留率不受任何条件的影响,基本稳定在97%。葡萄糖截留率随木质素浓度的增加而增加,并随错流速率的增加而减小。在0.8 g/L的木质素质量浓度条件下,当错流速率从0.12 m/s增加到0.17 m/s时,葡萄糖截留率从14%减小到7.3%。由此可见,在混合溶液的超滤过程中,通过合理选择错流速率,能够改善木质素和葡萄糖的分离。     

胸腺五肽纳滤浓缩过程研究

采用间歇浓缩方式,研究了纳滤对胸腺五肽离子交换洗脱液的浓缩特性。采用纳滤浓缩模型预测胸腺五肽离子交换洗脱液纳滤过程,系统考察透过通量和胸腺五肽浓度等随过程时间的变化。实验结果表明：截留相对分子质量为150的纳滤膜对胸腺五肽的截留率达到98．66％;胸腺五肽洗脱液透过通量随操作压力变化的结果表明,其纳滤过程为两机理控制;纳滤浓缩模型较好地模拟了胸腺五肽的纳滤浓缩过程,说明该模型适用于小分子多肽的纳滤浓缩过程。     

Pilot scale ceramic membrane microfiltration for Pichia pastoris cells separation in production of Rhizopus chinensis lipase

在重组毕赤酵母生产脂肪酶的提取中,应用并优化了陶瓷膜微滤除菌工艺,确定了最佳条件为膜截留分子量500 kDa、膜操作压力0.3 MPa、温度20℃、湿菌体含量35％,先对发酵液稀释1.5倍后再进行洗滤.40L处理量的小试结果显示,在5h处理时间内,能获得高达92.70％的酶活回收率.560 L处理量的中试放大,酶活回收率为89.91％,耗时5.5h.在膜的清洗与再生中,采用2％ NaClO和2％NaOH在60℃、0.3 MPa膜压力下进行清洗40 min,清水膜通量恢复率为98.14％.陶瓷膜与板框除菌的比较试验发现,两种方法都获得了微生物限量合格的产品和较高的酶活回收率,但陶瓷膜微滤的滤液微生物检出量更低,处理时间较短,动力能耗更低,易与超滤膜耦合提取,废水产生量更少,菌体废渣易于回收,是一种节能减排、清洁环保的新型除菌工艺.     

重组毕赤酵母产华根霉脂肪酶的陶瓷膜微滤除菌工艺研究

在重组毕赤酵母生产脂肪酶的提取中,应用并优化了陶瓷膜微滤除茵工艺,确定了最佳条件为膜截留分子量500kDa、膜操作压力0．3Ⅷa、温度20℃、湿菌体含量35％,先对发酵液稀释1．5倍后再进行洗滤。40L处理量的小试结果显示,在5h处理时间内,能获得高达92．70％的酶活回收率。560L处理量的中试放大,酶活回收率为89．91％,耗时5．5h。在膜的清洗与再生中,采用2％NaC10和2％NaOH在60℃、0．3MPa膜压力下进行清洗40min,清水膜通量恢复率为98．14％。陶瓷膜与板框除菌的比较试验发现,两种方法都获得了微生物限量合格的产品和较高的酶活回收率,但陶瓷膜微滤的滤液微生物检出量更低,处理时间较短,动力能耗更低,易与超滤膜耦合提取,废水产生量更少,菌体废渣易于回收,是一种节能减排、清洁环保的新型除茵工艺。     

截流荧光法研究米曲霉氨基酰化酶的快速胍变性动力学

 用荧光光谱法、截流荧光法和酶活力测定法研究了在盐酸胍溶液中米曲霉氨基酰化酶变性动力学。我们发现在4.8mol/L盐酸胍溶液作用下(0.05mol/L磷酸缓冲溶液,pH7.4,25℃),氨基酰化酶二聚体解离成单亚基过程是一个十分快速的过程,反应速率常数k为3361l/s,即约需3ms时间完成;而单亚基分子的构象变化需要约20min方能到达平衡态,这是一个逐渐变化的缓慢过程。酶分子在胍作用下的失活现象同酶分子的结构变化紧密相关,在胍浓度大于4mol/L时酶完全失活。在高浓度盐酸胍下酶失活主要是因为酶二聚体迅速解离成单亚基的过程和单亚基构象逐渐变化的缓慢过程。双亚基解离常数大小标志着酶分子亚基间作用力的强弱。     

植物磷酸烯醇式丙酮酸羧化酶的研究——Ⅶ.PEP羧化酶必需赖氨酸残基的化学修饰

本文报道纯化的高粱叶片PEP 羧化酶经氨基修饰剂TNBS 和PLP 的修饰迅速失活。酶的TNBS 失活与保温时间和抑制剂浓度呈函数关系并表现为拟一级反应的特性。动力学资料表明酶仅被1分子TNBS 修饰即失活。TNBS 修饰酶的吸收光谱特性表明被修饰的是酶蛋白的赖氨酸残基。底物(PEP)和效应剂(G6P)保护酶免被TNBS 失活。计算G6P 和酶的解离常数K_d-2.39×10~(-3)M。酶的其他反应组分HCO_3~-和MgCl_2单独存在时均不影响TNBS 对酶的失活作用。在被TNBS 修饰过程中还导致酶对G6P 迅速脱敏,同时却保持酶对甘氨酸的敏感性。     

植物磷酸烯醇式丙酮酸羧化酶的研究——Ⅶ.PEP羧化酶必需赖氨酸残基的化学修饰

本文报道纯化的高粱叶片PEP羧化酶经氨基修饰剂TNBS和PLP的修饰迅速失活。酶的TNBS失活与保温时间和抑制剂浓度呈函数关系并表现为拟一级反应的特性。动力学资料表明酶仅被1分子TNBS修饰即失活。TNBS修饰酶的吸收光谱特性表明被修饰的是酶蛋白的赖氨酸残基。底物(PEP)和效应剂(G6P)保护酶免被TNBS失活。计算G6P和酶的解离常数K_d=2.39×10~(-3)M。酶的其他反应组分HCO_3~-和MgCl_2单独存在时均不影响TNBS对酶的失活作用。在被TNBS修饰过程中还导致酶对G6P迅速脱敏,同时却保持酶对甘氨酸的敏感性。     

MBR运行初期对基因工程菌的截留特性研究

在膜-生物反应器(MBR)中实施基因工程菌生物强化时,运行初期基因工程菌流失是生态风险评价的重要内容.在一体式微滤膜-生物反应器中,考察了运行初期不同运行条件对基因工程菌流失密度和截留效率的影响,并对截留特性进行了探讨.结果表明,膜-生物反应器运行初期,不同运行条件对基因工程菌的截留效率影响不同:污泥浓度增加,截留效率提高;提高膜通量和曝气量,截留效率降低.基因工程菌接种密度为1.0×1010CFU/mL时,不同运行条件下的流失密度为1.0×102 CFU/mL～2.5×102 CFU/mL,最大截留效率大于8 lg.膜-生物反应器运行初期,膜组件截留、污泥吸附以及对悬浮细胞迁移阻碍是影响截留效率的主要因素,一定条件下其截留效率贡献率分别为82.3%、14.9%和2.8%.膜-生物反应器稳定运行过程中形成凝胶层,可以提高截留效率.一定条件下,膜组件、污泥和凝胶层对基因工程菌的截留贡献率分别为75.3%、10.7%和14.0%.     

超滤法浓缩谷氨酰胺转胺酶的影响因素研究

对微生物谷氨酰胺转胺酶(MTG)超滤浓缩的工艺条件进行了探讨及优化。实验采用截留分子量为30 kDa的聚醚砜(PES)膜,当发酵液初始pH为7,超滤浓缩倍数为4倍时,可以得到理想的MTG回收率。同时对超滤液中蛋白酶的变化进行了分析,发现随着超滤倍数的提高蛋白酶也逐渐提高,但在浓缩4倍以后达到较稳定的水平。聚醚砜(PES)超滤膜使用后用稀释的NaOH溶液浸泡清洗处理50 min后,膜通量可以恢复98.12%。     

Comparison of the performance of submerged membrane bioreactor (SMBR) and submerged membrane adsorption bioreactor (SMABR)

This study focuses on comparing the performance of submerged membrane bioreactor (SMBR) and submerged membrane adsorption bioreactor (SMABR) over a period of 20 days at a hydraulic retention time (HRT) of 3.1h. The effects of PAC on critical flux and membrane fouling were also investigated. The SMABR exhibited better results in terms of mixed liquor suspended solids (MLSS) growth, DOC removal (over 96%), COD removal (over 95%), transmembrane pressure (TMP) and oxygen uptake rate. Nearly 100% of bacteria and 100% of total coliforms were removed in both systems. The addition of PAC could maintain the critical flux at a lower TMP value (7.5 kPa), while irreversible fouling caused by PAC occurred when the filtration flux exceeded critical flux.     

Production and separation of alpha-agarase from Altermonas agarlyticus strain GJ1B

This paper presents results on the production of alpha-agarase by a fermentation process and its separation using membrane microfiltration (MF). Optimization of fermentation conditions for alpha-agarase production using Altermonas agarlyticus grown on medium containing agar as a carbon source was done in batch, fed-batch and continuous fermentations. Continuous culture at a dilution rate of 0.03 h(-1) appeared to be best suited for production of alpha-agarase by this organism. At 0.03 h(-1) dilution rate, enzyme activity was 0.9 U/ml. Clarification of broth was done using a hollow-fibre microfiltration membrane. The influence of hydrodynamic parameters on permeate flux and enzyme activity was studied. The best performance was obtained with prefiltered fermentation broth. A stable permeate flux of about 250-270 ml/min.m2 and an enzyme retention rate between 0% and 25% was obtained at temperatures between 6 degrees C and 22 degrees C, transmembrane pressure of 100 mm Hg and fluid cross-flow velocity of 4 x 10(-2) m/s. From the experiments on concentration of fermentation broth, the best compromise between enzyme activity transmission and permeate flux was obtained at a concentration factor of 2.     

Internal virus polarization model for virus retention by the Ultipor® VF Grade DV20 membrane

Several recent studies have reported a decline in virus retention during virus challenge filtration experiments, although the mechanism(s) governing this phenomenon for different filters remains uncertain. Experiments were performed to evaluate the retention of PP7 and PR772 bacteriophage through Ultipor VF Grade DV20 virus filters during constant pressure filtration. While the larger PR772 phage was fully retained under all conditions, a 2‐log decline in retention of the small PP7 phage was observed at high throughputs, even under conditions where there was no decline in filtrate flux. In addition, prefouling the membrane with an immunoglobulin G solution had no effect on phage retention. An internal polarization model was developed to describe the decline in phage retention arising from the accumulation of phage in the upper (reservoir) layer within the filter which increases the challenge to the lower (rejection) layer. Independent support for this internal polarization phenomenon was provided by confocal microscopy of fluorescently labeled phage within the membrane. The model was in good agreement with phage retention data over a wide range of phage titers, confirming that virus retention is throughput dependent and supporting current recommendations for virus retention validation studies. These results provide important insights into the factors governing virus retention by membrane filters and their dependence on the underlying structure of the virus filter membrane. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:856–863, 2014     

Cross flow filtration of RNA extracts by hollow fiber membrane

The feasibility of using ultrafiltration to concentrate RNA was investigated. Ultrafiltration flux and solute retentivity were affected by membrane cut-off and inlet pressure. The RNA can be concentrated by selecting a hydraulically permeable membrane (PM 30) and then operating the system at a sufficiently high pressure (2.07 · 10⁵ Nm⁻²) and a high recirculation rate (150 cm⁻¹). The use of this procedure was limited to a high-flux regime. However, a very high retentivity of macrosolute was achieved. The effect of transmembrane pressure on the apparent mass transfer coefficient in the “gel polarization model” was discussed and related to ultrafiltration flux.     

Role of some whey components on mass transfer in ultrafiltration

Ultrafiltration through Carbosep M(4) mineral membrane of protein solutions of decreasing complexity (whey before and after centrifugation or clarification, beta-lactoglobulin) was studied. Mathematical models were used to explain variations in flux with time. Taking into account variations in protein retention and hydraulic resistance of the membrane during ultrafiltration, proteins and lipoproteins were found to be involved not only in the polarization layer (reversible fouling leading to a difference in the osmotic pressure), but also in irreversible fouling by adsorption. Morever, the presence of particles (e.g., inorganic precipitates) in whey explains the build-up of a deposit over and within the membrane which contributes to the decline in flux after 1 h ultrafiltration. The relative importance of these phenomena was quantified.     

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.     

膜-生物硝化反应器处理含氨废水效能的研究

研究了膜 生物硝化反应器对含氨废水的处理效能以及分离膜的截留和渗透效能。膜_生物反应器启动迅速 ,在水力停留时间为 1d的情况下 ,反应器最高进水浓度达 80mmol(NH₄⁺-N)·L^-1 ,最高容积负荷达 1 12kg(NH₄⁺ -N)·m^-3·d^-1 ,氨氮去除率保持在 95%以上。试验证明 ,分离膜对微生物有良好的截留作用 ,50天内反应器的污泥浓度从 5g·L^-1 增长到 10g·L^-1 ,分离膜表面附着的生物层则对废水氨氮和亚硝氮有进一步的转化作用。在液位差低于 80cm时 ,提高液位差可增大膜渗透通量 ;液位差超过 80cm后 ,增大液位差的膜渗透通量效应很小 ;其中 ,当液位差为 2 0cm左右时 ,膜通量达 2 . 5 1L·m^-2 ·h^-1 ,阻力最小 [(2 . 6 3× 10^-5)m^-1]。该膜_生物硝化反应器可依靠液位差压力驱动出水 ,无需外加动力。     

Recovery of ammonium lactate and removal of hardness from fermentation broth by nanofiltration

Nanofiltration (NF) was investigated as an alternative to desalting electrodialysis (ED) and ion exchange for the recovery of ammonium lactate from fermentation broth. Three commercial NF membranes, NF45, NF70, and NTR-729HF, were characterized with 50 mM NaCl, MgSO(4), and glucose solutions. NF45 membrane was selected because it showed the lowest rejection of monovalent ion, the highest rejection of divalent ion, and the highest rejection of nonpolar molecule. Effects of the operating pressure were investigated in a range of 100-400 psig, on the flux, lactate recovery, and glucose and magnesium removal from a real fermentation broth containing about 1.0 M of ammonium lactate. The flux and recovery rate increased linearly with the pressure. However, lactate rejection also increased with the pressure, lowering the recovery yield. More magnesium ions and glucose were rejected as the pressure was increased, and at 400 psig, for example, magnesium ion was almost completely rejected, highlighting the chance of obviating the necessity of ion exchange to remove hardness, by using NF instead of desalting ED. Membrane fouling was not so severe as expected, considering the complex nature and a rather high concentration of the fermentation broth treated.