Effect of dilution rate on growth, productivity, cell cycle and size, and shear sensitivity of a hybridoma cell in a continuous culture

To study the effects of the growth rate of the hybridoma cell Mn12 on productivity, cell cycle, cell size, and shear sensitivity, six continuous cultures were run at dilution rate of 0.011, 0.021, 0.023, 0.030, 0.042, and 0.058 h(-1). This particular hybridoma cell appeared to be unstable in continuous culture with respect to specific productivity, as a sudden drop occurred after about 30 generations in continuous culture, accompanied by the appearance of two populations with respect to the cytoplasmic lgG content. The specific productivity increased with increasing growth rate. The shear sensitivity of the cell, as measured in a small air-lift loop reactor, increased with increasing growth rate. The mean relative cell size, as determined with a flow cytometer, increased with increasing growth rates. Furthermore, the fraction of cells in the S phase increased, and the fraction of cells in the G1/G0 phase decreased with increasing growth rates. (c) 1993 John Wiley & Sons, Inc.     

渗透压对硝化作用的影响

在气升式内循环硝化反应器中研究了渗透压对硝化作用的影响。保持进水氨氮浓度420mg·L-1,将进水渗透压逐渐从4.3×105Pa提高到18.8×105Pa,硝化反应器的氨氮转化率稳定在93%～100%。将进水渗透压进一步提高到19.2×105Pa,氨氮转化率降至69.2%。渗透压对硝化作用的影响具有突发性,临界值在18.8×105～19.2×105Pa之间。受高渗透压胁迫时,活性污泥中硝化细菌的形态趋向单一,个体变小,内膜数量减少,并产生许多不明成分的颗粒状内含物。解除渗透压胁迫后,细胞结构恢复。添加钾离子能够缓解高渗压对硝化作用的影响。高渗透压胁迫以及解除渗透压胁迫可增强污泥硝化活性,比污泥氨氮转化率(污泥以SS计)分别从0.083kg·kg-1·d-1升至0.509kg·kg-1·d-1和2.569kg·kg-1·d-1,同比提高5.1倍和30.0倍。     

Fluid shear effects on suspension cultures of Morinda citrifolia

The shear susceptibility of cell suspension cultures of the plant cell Morinda citrifolia was investigated by subjecting the cells to the well-defined shear field generated in turbulent flow through a capillary. Suspensions were circulated using a peristaltic pump and average shear stresses between 25 and 350 N m(-2) were generated in the capillary test section. Control experiments were performed to assess the possible contribution of the peristaltic pump to the observed cell damage. There was clear evidence of pump-induced damage at the more severe test conditions and all viability measurements were corrected accordingly. Both shake flask suspension cultures (aged between 9 and 15 days) and repeated batch fermentation cultures, grown in a stirred tank reactor (STR) under a variety of controlled agitation conditions, were tested in the capillary shear loop. The cell damage incurred was evaluated in terms of suspension viability, as determined by a dye exclusion technique. Viability loss was found to conform closely to a first-order model in which the rate constant was observed to increase with the imposed shear stress. Furthermore, a linear relationship was identified between the specific death constant and the cumulative energy dissipated. Post-shear morphological measurements showed that the chain length distribution is shifted toward markedly lower values. In comparison with shake flask cultures, repeated batch fermentation cultures exhibited a marked increase in sensitivity to capillary shear. Based upon the determined morphological characteristics, this result is primarily attributable to the increased chain lengths characteristic of the repeated batch cultures. (c) 1995 John Wiley & Sons, Inc.     

Oxygen transfer in liquid-impelled loop reactors using perfluorocarbon liquids

Oxygen transfer in the liquid-impelled loop reactor is described for a setup in which the perfluorochemical FC40 is aerated externally. Two sizes of reactors are investigated. The mass-transfer coefficient k appears to be lower with a factor of about 0.6 compared to gas liquid systems. the specific exchange area in the present experimental setup is found to be favorable when compared with gas liquid bioreactors at the same superficial dispersed-phase velocities. However, slow coalescence of the dispersed-phase drops in the phase separation section limits the dispersed-phase flow rate seriously. In Case this become crucial from the point of view of oxygen supply, special measures need to be found or alternatives such as combined sparging of air and solvent. (c) 1992 John Wiley & Sons, Inc.     

Adhesion of the marine fouling diatom amphora coffeaeformis to non‐solid gel surfaces

Diatom adhesion to different gel surfaces was tested under different shear conditions, using the fouling marine diatom Amphora coffeaeformis as test organism. Four polymers were selected to obtain a test matrix containing gels with different surface charge as well as different surface energies, viz. agarose, alginate, chitosan and chemically modified polyvinylalcohol (PVA‐SbQ). Three experimental systems were applied to obtain different shear rates. Experimental system 1 consisted of gels cast in a cell culturing well plate for comparing initial adhesion as well as long term biofilm development in the absence of shear. In experimental system 2, microscope slide based test surfaces were tested in aquaria under low shear conditions. A rotating annular biofilm reactor was used to obtain high and controlled shear rates. At high shear rates A. coffeaeformis cells adhered better to the charged polymer gels (alginate and chitosan) than to the low charged polymer gels (agarose and PVA‐SbQ). In the system where shear was absent A. coffeaeformis cells developed a biofilm on agarose equivalent to the charged polymer gels, while adhesion to PVA‐SbQ remained low at all shear rates. It is concluded that non‐solid surfaces did not represent an obstacle to settling and growth of this organism. As observed for solid surfaces, low charge density led to reduced attachment, particularly at high shear.     

Co-immobilized aerobic/anaerobic mixed cultures in stirred tank and gaslift loop reactors

Co-immobilized Aspergillus awamori and Zymomonas mobilis cultures were investigated in a stirred tank reactor on synthetic medium with starch as substrate at various dissolved oxygen concentrations. In a gaslift loop reactor, freely suspended and immobilized A. awamori were cultivated on synthetic medium and soluble potato starch. In the same reactor, the growth and ethanol production of freely suspended and immobilized Z. mobilis cultures were studied on synthetic medium and glucose. Co-immobilized A. awamori and Z. mobilis were cultivated in batch and continuous operations in the gaslift loop reactor on synthetic medium with starch substrate at different dissolved oxygen concentrations. The interrelations between the different process variables are discussed.     

低高径比喷射环流生化反应器流体力学和发酵性能的研究

对高径比s≤2．5喷射环流生化反应器的流体力学和传质特性进行了系统的研究,选出反应器的最佳结构,关联出氧的体积传递系数(k_La)表达式。在此基础上,进行了谷氨酸发酵试验,摸索出用该设备进行各氨酸发酵的最佳工艺条件,使5批一次性投糖发酵的糖酸转化率达到50％以上。     

Cheese whey treatment performance of an aerobic jet loop membrane bioreactor

The raw chess whey (CW) treatment capacity of a jet loop membrane bioreactor (JLMBR) was evaluated. Raw CW was first characterized for carbonaceous, nitrogenous and phosphorus compounds. The total COD range of the raw CW was between 73 and 86 kg m⁻³ and 82% of the total COD was found to be soluble. The JLMBR system, of 32 l capacity was operated continuously for 3 months with a sludge age of 1.1–2.8 days and COD loads of 3.5–33.5 kg-COD m⁻³ per day. A treatment efficiency of 97% was obtained for 1.6 days of sludge age and COD loads of 22.2 kg-COD m⁻³ per day. The sludge flocks observed in the system were highly motile, dispersed and had poor settling properties. The membrane filtration characteristics of this sludge were investigated and increasing MLSS concentration decreased membrane flux values.     

内循环颗粒污泥床硝化反应器临界曝气强度的研究

内循环颗粒污泥床硝化反应器是一种新型高效硝化反应器 ,在反应器运行过程中 ,液体循环临界曝气强度和颗粒污泥流化临界曝气强度是两个重要操作参数。建立了升流区表观液速Ulr与曝气强度Ugr之间的关系 ,并测定了有关的模型参数 ,得到了具体的数学表达式 :U_lr=(2.613-0.024 )U^0.871_gr 0.276U^0.871_gr-0.28。根据该模型 ,计算得到的液体循环临界曝气强度为1.017cm/min ,颗粒污泥流化临界曝气强度为 2.662cm/min。实测结果证明 ,求得的两个临界曝气强度具有较高的准确性 ,能够用于指导内循环颗粒污泥床硝化反应器的操作优化.     

Characterization of a pilot plant airlift tower loop bioreactor: II. Evaluation of global mixing properties of the gas phase during yeast cultivation

Saccharomyces cerevisiae was cultivated in a 4-m(3) pilot plant airlift tower loop reactor with a draft tube in batch and continuous operations and for comparison in a laboratory airlift tower loop reactor of 0.08 m(3) volume. The reactors were characterized during and after the cultivation by measuring the distributions of the residence times of the gas phase with pseudostochastic tracer signals and mass spectrometer and by evaluating the mixing in the liquid phase with a pulse-shaped volatile tracer signal and mass spectrometer as a detector. The mean residence times and the intensities of the axial mixing in the riser and downcomer, the circulation times of the gas phase, and the fraction of the recirculated gas phase were evaluated and compared.     

含羞草(Mimosa pudica L.)叶片匀浆悬浮液的滞后环

由于受力后叶子立即发生运动 ,含羞草是一个研究力对于生物细胞作用的良好模型。在以往的研究中 ,人们认为此种现象与受力后渗透压改变、离子通道被激活、细胞骨架的动态变化有关。该文旨在通过观察含羞草叶片和叶柄匀浆悬浮液的应力 切变率滞后环变化 ,揭示含羞草的力学性质。在用于比较的含羞草、叶下珠和猪骨骼肌匀浆悬浮液以及水 4个系统中 ,只有含羞草系统具有明显的逆时针滞后环轨迹 ,而其它的 3个系统均不存在。以上结果提示 ,在含羞草的匀浆悬浮液系统中 ,有一种或多种物质 (可能是蛋白质和细胞骨架 )在剪切应力作用过程中由颗粒状结构向网状结构转变 ,由无序结构向有序结构转变 ,由液体结构向黏弹性状态转变 ,而当力撤除以后再缓慢恢复。