Influence of a swirl motion on the interaction between microalgal cells and environmental medium during ultrafiltration of a culture of Tetraselmis suecica

The role of the environmental medium of a marine microalga culture (Tetraselmis suecica) in membrane fouling phenomenon is quantified for two ultrafiltration units: one generating a classical tangential plane flow and another involving a swirling decaying flow induced by a tangential inlet. Compared to the plane unit, the swirling configuration increases the performances of the ultrafiltration process (augmentation of 20% in terms of limiting flux). Interactions between the culture medium and cells depend on the module design. Furthermore, experiments emphasize the significant role of the particles whatever the module design: more than 70% of the total hydraulic resistance could be due to the microalgal cells, while about 30% of membrane fouling is relevant to soluble materials.     

Swirling flow implementation in a photobioreactor for batch and continuous cultures of Porphyridium cruentum

Light is the main limiting factor in photoautotrophic-intensive production of microorganisms, and improvement of its use is an important concern for photobioreactor design and operation. Swirling flows, which are known to improve mass and photon transfers, were applied to annular light chambers of a photobioreactor and studied by simulation and microalgal culture. Two hydrodynamic conditions were compared: axial flow generating poor radial mixing, and tangential flow generating three-dimensional swirling motion. Batch and continuous cultures of the Rhodophyte Porphyridium cruentum were performed in a 100-L, 1.5-m(2), fully controlled photobioreactor with eight light chambers. The inlet design of these chambers was modified to create the hydrodynamic conditions for comparison. Various intensities of swirling motion were used, characterized by the velocity factor (VF), defined as the ratio between annular chamber flow and inlet aperture sections. Experiments were performed within the range of photon flux densities (PFD) optimizing the yield of light energy transformation into living substance for the species and the temperature used. Culture kinetics with swirling flows generated by apertures of VF = 2, 4, and 9 were compared with pseudoaxial VF = 2 chosen as reference. Batch cultures with VF = 4 swirling flow showed no significant difference, whereas continuous cultures proved more discriminating. Although no significant difference was obtained for VF = 2, a 7% increase of steady-state productivity and a 26% decrease in time required to reach this steady state were obtained with VF = 4 swirling flow. This beneficial effect of swirling flow could have accounted for increased mixing. Conversely, VF = 9 swirling flow resulted in a 9% decrease of steady-state productivity and a 9% increase in the time required to reach this steady state, a negative effect that could have accounted for increased shear stress. CO(2) bioconversion yield at steady state showed a 34% increase for VF = 4. These results suggest that swirling motion makes microalgal cultures more efficient, provided that the resulting adverse effects remain acceptable. Experimental investigation was completed by a theoretical approach in which simulation of continuous cultures of P. cruentum was based on the hydrodynamic conditions achieved in the photobioreactor. Although the results obtained with pseudoaxial flow were correctly predicted, simulations with swirling flow showed a marked enhancement of productivity not observed experimentally. The influence of side effects induced by increased mixing (particularly hydrodynamic shear stress) was considered with respect to modeling assumptions. Comparison of experimental results with theoretical simulation provided a better understanding of the mixing effect, a key factor in improving the efficiency of such bioprocesses.     

Variation in Storage α-Polyglucans of Red Algae: Amylose and Semi-Amylopectin Types in <Emphasis Type="Italic">Porphyridium</Emphasis> and Glycogen Type in <Emphasis Type="Italic">Cyanidium</Emphasis>

Red algae are widely known to produce floridean starch but it remains unclear whether the molecular structure of this algal polyglucan is distinct from that of the starch synthesized by vascular plants and green algae. The present study shows that the unicellular species Porphyridium purpureum R-1 (order Porphyridiales, class Bangiophyceae) produces both amylopectin-type and amylose-type alpha-polyglucans. In contrast, Cyanidium caldarium (order Porphyridiales, class Bangiophyceae) synthesizes glycogen-type polyglucan, but not amylose. Detailed analysis of alpha-1,4-chain length distribution of P. purpureum polyglucan suggests that the branched polyglucan has a less ordered structure, referred to as semi-amylopectin, as compared with amylopectin of rice endosperm having a tandem-cluster structure. The P. purpureum linear amylose-type polyglucan, which has a lambda(max) of 630 nm typical of amylose-iodine complex and is resistant to Pseudomonas isoamylase digestion, accounts for less than 10% of the total polyglucans. We produced and isolated a cDNA encoding a granule-bound starch synthase (GBSS)-type protein of P. purpureum, which is probably the approximately 60-kDa protein bound tightly to the starch granules, resembling the amylose-synthesizing GBSS protein of green plants. The present investigation indicates that the class Bangiophyceae includes species producing both semi-amylopectin and amylose, and species producing glycogen alone.     

Variation in storage alpha-glucans of the Porphyridiales (Rhodophyta)

Storage glucans were analyzed in the Porphyridiales which include the most primitive and phylogenetically diverged species in the Rhodophyta, to understand early evolution of the glucan structure in the Rhodophyta. The storage glucans of both Galdieria sulphuraria and Cyanidium caldarium consisted of glycogen, while those of Rhodosorus marinus, Porphyridium purpureum, P. sordidum and Rhodella violacea could be defined as semi-amylopectin. X-ray diffraction analysis of the glucans demonstrated variation in the crystalline structure: the patterns in P. purpureum and R. violacea were of A- and B-types, respectively, while alpha-glucans of R. marinus and P. sordidum displayed structures with lower crystallinity. Electron microscopic observations indicated that the alpha-glucans of P. sordidum consisted of two kinds of granules; a minor component of more dense granules with crystalline leaflets and a major component of softer ones without crystalline structure. Gel permeation chromatography showed that all the species containing the semi-amylopectin-type glucans also contained amylose, although the relative amounts of this fraction were different depending on the species. Our results are consistent with two distinct evolution scenarios defined either by the independent acquisition of semi-crystalline starch-like structures in the different plant lineages or more probably by the loss of starch and reversion to glycogen synthesis in cyanidian algae growing in hot and acid environments.     

Membrane separation of protein precipitates: unstirred batch studies

The study examines the use of ultrafiltration and microfiltration membranes for concentrating isoelectric soya protein. Experiments with an unstirred batch cell indicate that the flux is limited by the protein which remains in solution after precipitation of the major proportion. The porosityof the precipitate cake formed is shown to be a second important factor. A significant improvement in flux can be obtained by using membranes which permit passage of the soluble protein and by increasing the precipitate particle size. The results are shown to be within the range predicted theoretically by the two limiting cases of a particulate model and a soluble protein model.     

Cd2+对紫球藻生长及光化学活性的影响

以紫球藻(Porphyridium purpureum)为供试材料, 研究了5个不同浓度的Cd2+对紫球藻的细胞密度、叶绿素a含量、藻红蛋白含量及ATP含量的影响, 以及对紫球藻的最大光量子产额(F_v/F_m)、实际光量子产额(YII)、相对电子传递效率(ETR)及非光化学淬灭(NPQ)的影响, 探讨了各荧光参数在不同浓度的Cd2+胁迫下的变化规律。研究结果表明, 在Cd2+胁迫的6d内, 紫球藻的生长速度显著下降, 且Cd2+的浓度越高, 生长速度下降越快; Cd2+胁迫显著的减少叶绿素a、藻红蛋白及ATP含量, 且浓度越高, 减少的幅度越大; 在Cd2+浓度低于200 μmol/L时, 紫球藻的叶绿素荧光参数F_v/F_m、YII及ETR呈现先下降后上升的趋势,而且随着胁迫时间的延长, 下降幅度逐步增大; NPQ在低浓度下(<200 μmol/L)呈现显著上升趋势, 高浓度下(>500 μmol/L)呈现显著下降趋势。因此, 水体中浓度超过50 μmol/L的Cd2+就会显著影响紫球藻的生长及光化学活性, 水生环境中不断累积的Cd2+将会对紫球藻的生态平衡产生影响。     

Porphyridium violaceum,eine marine neue Art

Zusammenfassung 1. Die neubeschriebene marinePorphyridium-Art unterscheidet sich von dem terrestrisch lebenden, aber auch im Meerwasser gefundenenPorphyridium purpureum durch ihre größeren, violett gefärbten Zellen.2. Teilung und Wachstum der Zellen vonPorphyridium violaceum passen sich dem Belichtungsrhythmus an. Die während der 10stündigen Dunkelheit geteilten Zellen sind 9 bis 11µ dick, sie vergrößern sich während der Lichtperiode auf 11 bis 14µ.

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Porphyridium violaceum, a marine new species

The new species is marine, whereasPorphyridium purpureum (= P. cruentum), first known only from terrestrial habitats, is halophilic and has been found several times in seawater.Porphyridium violaceum differs from the above mentioned species by a larger diameter and the colour of its cells.

     

Induced cultivation pattern enhanced the phycoerythrin production in red alga Porphyridium purpureum

Bioprocess and Biosystems Engineering - Porphyridium purpureum is a rich source for producing phycoerythrin (PE); however, the PE content is greatly affected by culture conditions. Researchers have...     

Production of tomato flavor volatiles from a crude enzyme preparation using a hollow-fiber reactor

In recent years there has been an increase in the interest in the production of compounds by isolation from natural sources or through processes that can be deemed "natural". This is of particular interest in the food and beverage industry for flavors and aromas. Hexanal, organoleptically known to possess "green character", is of considerable commercial interest. The objective of this study was to determine if the enzyme template known to be responsible for the synthesis of hexanal from linoleic acid (18:2) in tomato fruits could be harnessed using a hollow-fiber reactor. A hollow-fiber reactor system was set up and consisted of a XAMPLER ultrafiltration module coupled to a reservoir. The enzyme template was extracted from ripe tomato fruits and processed through an ultrafiltration unit (NMWC of 100 kDa) to produce a retentate enriched in soluble and membrane-associated lipoxygenase (LOX) and hydroperoxide lyase (HPL). This extract was recirculated through the lumen of the hollow-fiber ultrafiltration unit with the addition of substrate in the form of linoleic acid, with buffer addition to the reaction flask to maintain a constant retentate volume. Product formation was measured in the permeate using solid phase microextraction (SPME) developed for this system. At exogenous substrate concentrations of 16 mM and a transmembrane pressure of 70 kPa, hexanal production rates are in the order of 5.1 microg/min. Addition of Triton X-100 resulted in membrane fouling and reduced flux. The reactor system has been run for periods of up to 1 week and has been shown to be stable over this period.     

Membrane separation of protein precipitates: Studies with cross flow in hollow fibers

Hollow fiber ultrafiltration and microfiltration membranes are examined for the processing of isoelectric soya protein precipitate suspensions. A model based on the various resistances to permeate flux is used to describe membrane performance. The main resistance to permeate flux is due to the interaction between the active membrane and the soluble and precipitated protein; that is, as compared with resistances due to the active membrane itself or the membrane support structure, or arising from concentrated soluble or precipitated protein layers over the membrane surface. Soluble protein rejection and precipitate mean particle diameter are correlated with observed values of this main resistance.In contract to the ultrafiltration of soluble proteins, the flux rates observed when processing protein precipitate suspensions under a similar range of operating conditions do not approach a limiting value with increased transmembrane pressure. At high protein concentrations, greater flux rates may be achieved for precipitated as compared with soluble proteins. The use of a microfiltration membrane does not give further improvement in flux rate; this may be attributed to problems of pore fouling with precipitate particles.     

Ultrafiltration of highly concentrated antibody solutions: Experiments and modeling for the effects of module and buffer conditions

Although ultrafiltration is currently used for the concentration and formulation of nearly all biotherapeutics, obtaining the very high target concentrations for monoclonal antibody products is challenging. The objective of this work was to examine the effects of the membrane module design and buffer conditions on both the filtrate flux and maximum achievable protein concentration during the ultrafiltration of highly concentrated monoclonal antibody solutions. Experimental data were obtained using both hollow fiber and screened cassettes and in the presence of specific excipients that are known to alter the solution viscosity. Data were compared with predictions of a recently developed model that accounts for the complex thermodynamic and hydrodynamic behavior in these systems, including the effects of back‐filtration arising from the large pressure drop through the module due to the high viscosity of the concentrated antibody solutions. Model calculations were in good agreement with experimental data in hollow fiber modules with very different fiber length and in screened cassettes having different screen geometries. These results provide important insights into the key factors controlling the filtrate flux and maximum achievable protein concentration during ultrafiltration of highly concentrated antibody solutions as well as a framework for the development of enhanced ultrafiltration processes for this application. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:692–701, 2016     

Efficient cultivation of Porphyridium purpureum integrated with swine wastewater treatment to produce phycoerythrin and polysaccharide

Journal of Applied Phycology - In the present study swine wastewater diluted at the different percentages (10%, 20%, 60%, and 100%) was used to cultivate the red alga Porphyridium purpureum to...     

A new photobioreactor for continuous microalgal production in hatcheries based on external-loop airlift and swirling flow

This study deals with the scale of a new photobioreactor for continuous microalgal production in hatcheries. The combination of the state-of-art with the constraints inherent to hatcheries has turned the design into a closed, artificially illuminated and external-loop airlift configuration based on a succession of elementary modules, each one being composed of two transparent vertical interconnected columns. The liquid circulation is ensured pneumatically (air injections) with respect to a swirling motion (tangential inlets). A single module of the whole photobioreactor was built-up to scale its geometry (diameter and length) and to optimize its design (air sparger, tangential inlets). The volumetric productivities were predicted by modeling radiative transfer and growth of Isochrysis affinis galbana (clone Tahiti). The hydrodynamics of the liquid phase was modeled in terms of global flow behavior (circulation and mixing times, Péclet number) and of swirling motion decay along the column (Particle Image Velocimetry). The aeration performances were determined by overall volumetric mass transfer measurements. Continuous cultures of Isochrysis affinis galbana (clone Tahiti) were run in two geometrical configurations, generating either an axial or a swirling flow. Lastly, the definitive options of design are presented as well as a 120-L prototype, currently implemented in a French mollusk hatchery and commercialized.     

An automated monitoring system using on-line ultrafiltration and column liquid chromatography for Aspergillus niger fermentations

An automated system for the monitoring of fermentations of filamentous fungi is described. The system is based on the on-line combination of ultrafiltration, for the removal of cellular and macromolecular material from the fermentation broth. and column liquid chromatography for analysis of the filtrate. The performance of one hollow-fibre and two planar ultrafiltration modules is evaluated. The maximum sampling frequency as well as prevention from clogging by mycelium is strongly dependent on the construction of the module, best results being obtained with a planar membrane and a relative high flow rate (150 ml/min) of the broth through a single, wide-bore (3 mm) flow channel in the module. The method is used for the study of metabolic and regulatory processes of two different Aspergillus niger strains on multiple carbon sources. The selected system can be applied for at least 70 h without any negative effect on either the fermentation or the analytical system. Through an analysis frequency of once per hour detailed information regarding consumption and production of nine different compounds could be obtained.     

Purification of densonucleosis virus by tangential flow ultrafiltration

Purification at commercial scale of viruses and virus vectors for gene therapy applications and viral vaccines is a major separations challenge. Tangential flow ultrafiltration has been developed for protein purification. Here tangential flow ultrafiltration of parvoviruses has been investigated. Because these virus particles are small (18-26 nm), removal of host cell proteins will be challenging. The results obtained here indicate that 30, 50, and 100 kDa membranes reject the virus particles, whereas 300 kDa membranes allow some virus particles to pass into the permeate. The decrease in permeate flux for the 300 kDa ultrafiltration membrane is much greater than for the 30, 50, and 100 kDa membranes, indicating possible entrapment of virus particle in the membrane pores. The permeate flux and level of protein rejection is strongly affected by the cell culture growth medium. The results indicate that when developing a new process, it is essential that the cell culture and purification operations be developed in parallel.     

Cryopreservation of economically valuable marine micro-algae in the classes Bacillariophyceae, Chlorophyceae, Cyanophyceae, Dinophyceae, Haptophyceae, Prasinophyceae, and Rhodophyceae

The ability to routinely cryopreserve micro-algal species reduces costs associated with maintaining large culture collections and reduces the risks of losing particular strains or species through contamination and genetic drift. Cryopreservation is also a useful adjunct in aquaculture hatcheries for strains of micro-algae where the nutritional status may change as a result of continuous sub-culture. In this study, cryopreservation of isolates from seven micro-algal classes was investigated. Successful candidates included the marine dinoflagellates Amphidinium carterae, Amphidinium trulla, and Gymnodinium simplex, and the haptophytes Chrysochromulina simplex, Prymnesium parvum, Prymnesium parvum f. patelliferum, Isochrysis galbana, and Pavlova lutheri. Also successfully cryopreserved were the planktonic diatoms Chaetoceros calcitrans, Chaetoceros muelleri, Chaetoceros sp., and the benthic Nitzschia ovalis, the chlorophyte Chlamydomonas coccoides, the rhodophyte Porphyridium purpureum, the prasinophytes Tetraselmis chuii, and Tetraselmis suecica, and the cyanophytes Raphidiopsis sp., and Aphanizomenon flos-aquae. All species were successfully cryopreserved using 15% Me2SO.     

Salt-induced changes in plasmid DNA transmission through ultrafiltration membranes

Recent studies have demonstrated the feasibility of using ultrafiltration for the purification of plasmid DNA, but there is still little understanding of the factors governing DNA transmission. Experimental data were obtained for the transmission of a 3.0 kbp supercoiled plasmid DNA through composite regenerated cellulose ultrafiltration membranes as a function of solution ionic environment in a stirred ultrafiltration cell. The dependence on salt concentration was quite dramatic, with the sieving coefficient increasing by more than 80-fold as the NaCl concentration increased from 1 to 150 mM at a fixed filtrate flux. At the same total ionic strength, the sieving coefficient in an MgCl2 solution was significantly larger than that evaluated in NaCl. The sieving results are consistent with independent studies showing a reduction in the effective plasmid size due to salt specific shielding of intramolecular electrostatic interactions. DNA transmission was also a strong function of the filtrate flux, with negligible transmission below a critical value of the flux. The predicted values of the critical filtrate flux determined using a modified elongational flow model were in excellent agreement with the experimental data. These results clearly demonstrate that salt-induced changes in plasmid DNA structure have a significant effect on plasmid DNA transmission through ultrafiltration membranes.     

Light/dark cycles in the growth of the red microalga porphyridium sp

The effect of light/dark cycles on the growth of the red microalga Porphyridium sp. was studied in a tubular loop bioreactor with light/dark cycles of different frequencies and in two 35-L reactors: a bubble column reactor and an air-lift reactor. Photon flux densities were in the range of 50 to 300 μE m-2 s-1, and flow rates were 1 to 10 L min-1. Under conditions of low illumination and high flow rates, similar results were obtained for the bubble column and air-lift reactors. However, higher productivities-in terms of biomass and polysaccharide-were recorded in the air-lift reactor under high light intensity and low gas flow rates. The interactions of both photosynthesis and photoinhibition with the fluid dynamics in the bioreactors was taken as the main element that allowed us to interpret the differences in performance of the bubble column and the air-lift reactor. It is suggested that the cyclic distribution of dark periods in the air-lift reactor facilitates better recovery from the photoinhibition damage suffered by the cells. Copyright 1998 John Wiley & Sons, Inc.     

Direct measurement of species-specific cohesion in cellular slime molds

Partially differentiated cells of two species of cellular slime molds, Dictyostelium discoideum and Dictyostelium purpureum, were labeled with isothiocyanate derivatives of fluorescent dyes. The labeled cells of each species segregated promptly when mixed and placed on moist filters. We determined whether cells studied at a time when they demonstrated this capacity to segregate showed a preferential adherence to cells of the same species. When labeled dissociated cells of each species were interacted with an unlabeled immobilized layer of cells of each species under appropriate conditions, binding was, in part, species-specific.