Calcium alginate immobilized hybridomas grown using a fluidized-bed perfusion system with a protein-free medium

Hybridoma SPO1 cells were immobilized in calcium alginate beads and were further grown in a fluidized-bed perfusion system with a protein-free medium. The presence of serum in the steps of entrapment was shown to be helpful for the preservation of cell viability. Each step during immobilization was investigated with respect to the extent of cell damage caused. The immobilization process using small beads caused a lower cell viability initially but allowed a higher rate of cell growth subsequently, compared to those in large beads. In a perfusion system for the continuous production of monoclonal antibodies (MAb), the viable cell density reached 2×10⁷ cells per ml of beads with a viability of 40%. Compared with the cells in suspension culture, the immobilized SPO1 cells showed higher viable cell based specific rates of substrate uptake (glucose and glutamine) and of MAb production. A significant drop in the formation of lactate after the cell growth entered a steady state suggested a higher activity of the Tricarboxylic Acid Cycle in the cells when the cell density became high.     

Development of a novel, multi-analyte biosensor system for assaying cell division: identification of cell proliferation/death precursor events

A novel, miniaturized biosensor system was created by combining the electrophysiological response of immobilized cells with superoxide-sensing technology, optical and fluorescence microscopy. Vero cells were immobilized in a calcium alginate matrix (at a density of 1.7 x 10(6) cells ml(-1)). A 0.5 cm x 0.5 cm piece of cell-containing gel matrix was aseptically adhered on a glass microscope slide with a microfabricated gold electrode array, sealed with a cover slip and provided with Dulbecco's medium +10% (v/v) fetal calf serum every day by means of a capillary feeding tube. During a culture period of 7 days, the membrane potential of immobilized cells was continuously monitored, while cell division was assayed with an optical microscope. In addition, daily measurements of immobilized cell membrane potential, viability, RNA and calcium concentration, radical oxygen species (ROS) and glutathione accumulation, were conducted by fluorescence microscopy after provision of an appropriate dye. Superoxide accumulation was assayed by covering the electrodes with superoxide dismutase (SOD). Maximum cell membrane potential values and superoxide production were observed upon initiation of cell division. Using the novel biosensor, we were able to correlate seven different cell physiological parameters to each other and formulate a model for ROS-mediated signaling function on cell division and death. In addition, we were able to predict cell proliferation or death by comparing the relative response of the electrophysiological and superoxide sensor during the culture period.     

Cell immobilization using PVA crosslinked with boric acid

A new cell immobilization technique is described in which polyvinyl alcohol is crosslinked with boric acid, with the addition of a small amount of calcium alginate. The presence of the calcium alginate improves the surface properties of the beads, preventing agglomeration. A pure culture of phenol-degrading Pseudomonas was immobilized in the PVA-alginate beads. Phenol was successfully degraded in a fluidized bed of the beads, indicating that cell viability was maintained following the immobilization procedure. The PVA-alginate beads proved to be very strong and durable, with no noticeable degradation of the beads after 2 weeks of continuous operation of the fluidized bed.     

Covalent stabilization of alginate gel for the entrapment of living whole cells

Summary Three methods were developed for preparing alginate gels containing cells that are stable in phosphate containing media. In Method I preformed alginate beads containing entrapped cells were treated with polyethyl eneimine followed by glutaraldehyde. In Method II alginate sol was treated with a carbodiimide and N-hydroxysuccinimide (to form active esters), mixed with cells and extruded into calcium chloride solution. The beads were subsequently cross-linked with polyethyleneimine. In Method III alginate so] was treated with periodate (to form aldehyde groups), mixed with cells and extruded into calcium chloride solution. The beads were subsequently cross-linked with polyethyleneimine. Saccharomyces cerevisiae cells, immobilized in such stabilized gels, exhibited almost the same fermentation activity as the standard preparation. The viability of the immobilized cells was retained during the stabilization procedure as judged from their ability to multiply in the presence of nutrients.The preparations remained stable in phosphate buffer for at least ten days without substantial release of cells. The extent of cross-linking was controlled by varying the time and the concentration of reactants, thus giving preparations ranging from beads with a thin stabilized shell to beads homogeneously stabilized.     

Immobilization of Nicotiana tabacum plant cell suspensions within calcium alginate gel beads for the production of enhanced amounts of scopolin

Scopolin-producing cells of Nicotiana tabacum were immobilized within Ca-alginate gel beads. Free cell suspensions accumulated scopolin within cytoplasmic compartments and cell disruption was necessary to recover scopolin. On the contrary, immobilized plant cells excreted considerable amounts of scopolin. Scopolin diffused throughout the gel matrix and reached the culture media. A large fraction of produced scopolin could then be recovered from the culture medium without disrupting cells. Immobilized N. tabacum cells produced more scopolin than free cell suspensions did (3.8 mg/g fresh weight biomass [into the culture media] versus 0.2 mg/g fresh weight biomass [intracellular]). Variation of the immobilization conditions revealed a marked influence on the behavior of N. tabacum plant cells: production of scopolin and enhanced excretion, cell growth, and morphological aspect of plant cell colonies. This excretion phenomenon could be used advantageously at an industrial production level.     

Increasing the stability of immobilizedLactococcus lactis cultures stored at 4 °C

Summary Immobilized cell technology was used to prepare concentrated cultures ofLactococcus lactis that lost only 22% of viability over a 30-day storage period at 4°C. Concentrated cultures ofL lactis CRA-1 were immobilized in calcium alginate beads and added to glycerol, NaCl or sucrose-NaCl solutions in order to obtain a_w readings ranging from 0.91 to 0.97. The suspensions were subsequently placed at 4°C and viability (CFU g^–1 of bead) was followed during storage. Viability losses were high at a_w readings of 0.95 and 0.97 and pH dropped significantly (up to one unit) in the unbuffered solutions. Addition of 1% soytone or glycerophosphate helphed stabilize pH, and a beneficial effect on viability during storage was observed in the glycerol-soytone mix when the beads were added to the conservation solutions immediately following immobilization. When beads were added to the conservation solution immediately following immobilization, a 70% drop in cell counts occurred during the first 5 days of incubation. Dipping theL lactis-carrying beads in milk for 2h before mixing with the glycerolsoytone 0.93 a_w solution reduced this initial 5-day viability loss. Cultures grown in the alginate beads also had good stability in the 0.93 a_w glycerol-soytone solution, where 78% of the population was viable after 30 days at 4°C. The process could be used to store immobilized cells at a processing plant, or by suppliers of lactic starters who wish to ship cultures without freezing or drying.     

Immobilization of E. coli cells in polyacrylamide-based microporous cryogels

E. coli cells were immobilized in polyacrylamide cryogel by three ways: (1) introduction of cells in the reaction mixture followed by cryopolymerization; (2) the filling of the cryogel pores followed by cell fixation with diluted glutaric dialdehyde (GDA), and (3) the filling of the macropores of the polymeric matrix with modified surface. The ultrastructure of the gels and immobilized cells as well as distribution of attachment of the cells immobilized by different techniques were studied. The first type of immobilization was characterized by the highest quantity of the biomass in the gel (by protein) and by a sharp decrease of the cell viability. The second failed to retain the cells in the pores, and the GDA treatment significantly decreased the viability index. The latter technique was the mildest and completely maintained the viability of the population. However, the biomass content was lower as compared to the first type of immobilization, but could be considerably increased by the GDA treatment.     

Induction of stress metabolites in immobilized Glycyrrhiza echinata cultured cells

Transfer into a fresh medium or immobilization by entrapment in calcium alginate gels of cultured Glycyrrhiza echinata cells caused a rapid and transient accumulation of a retrochalcone, echinatin, in both the cells and the medium. The higher level and longer duration of echinatin production was observed in the immobilized cells than in freely suspended cells. Transfer of the cells into the medium containing either sodium alginate or calcium chloride, and the addition of sodium alginate into the suspension culture, caused the same effect as observed in cell immobilization. A novel metabolite was also detected in the induced cells. Activities of the enzymes involved in echinatin biosynthesis were shown to rapidly increase by immobilization of the cells.Abbreviations IAA indole-3-acetic acid - LMT S-adenosylmethionine: licodione 2-O-methyltransferase - CHS chalcone synthase     

Hybridoma cells in a protein-free medium within a composite gel perfusion bioreactor

A composite gel system has been developed combining the chemical and physical properties of calcium alginate and agarose gels. The results of growing composite gel immobilized hybridoma SPO1 cells in a protein-free medium within a fluidized-bed perfusion bioreactor are presented in this paper. During the continuous operation of this system, the total cell density reached 3.9×10⁷ cells per ml of beads (viability 79.6%). The specific productivity of monoclonal antibody of the immobilized hybridoma cells reached more than 1.5 g per 10⁶ viable cells per hour, compared with 0.5 for non-immobilized viable cells grown in a one liter agitated bioreactor with the same medium. Significant increases in cell metabolic activities, including substrate utilization and byproduct formation, were also observed. Leaching of materials from the beads was evident and the major fraction of released materials was alginate.     

Biomimetic CO₂ sequestration using purified carbonic anhydrase from indigenous bacterial strains immobilized on biopolymeric materials

The present study deals with immobilization of purified CA and whole cell of Pseudomonas fragi, Micrococcus lylae, and Micrococcus luteus 2 on different biopolymer matrices. Highest enzyme immobilization was achieved with P. fragi CA (89%) on chitosan-KOH beads, while maximum cell immobilization was achieved with M. lylae (75%) on chitosan-NH(4)OH beads. A maximum increase of 1.08-1.18 fold stability between 35 and 55°C was observed for M. lylae immobilized CA. The storage stability was improved by 2.02 folds after immobilization. FTIR spectra confirmed the adsorption of CA on chitosan-KOH beads following hydrophilic interactions. Calcium carbonate precipitation was achieved using chitosan-KOH immobilized P. fragi CA. More than 2 fold increase in sequestration potential was observed for immobilized system as compared to free enzyme. XRD spectra revealed calcite as the dominant phase in biomimetically produced calcium carbonate.     

Growth of poliovirus using alginate entrapped-anchorage dependant Vero cells

Obligatory anchorage dependant Vero cells were successfully grown in gelatinous-like macrocarriers made of calcium alginate. Entrapped single cells were immobilized within the polymerized alginate matrix divide to form large spherical clumps of cells. A cell density of 17×10⁶ cells/ml of alginate with over 95% viability was obtained after 14 days in spinner flasks. When subjected to poliovirus type I infection, spherical masses of Vero cells progressively showed extensive cytopathic effect but remained entrapped in the alginate matrix of the macrocarriers. Virus was released into a cellular debris free-like supernatant and reached a peak titer of 10^8.0 TCID₅₀/ml after 72 hours.     

Storage and growth of neuroblastoma cells immobilized in calcium-alginate beads

Summary Mouse neuroblastoma cells (N18) were immobilized in calcium-alginate gel beads. Under standard culture conditions (37° C; 5% CO₂), cell growth was observed inside the beads. The number of cells increased threefold during 7 days of culture with cell division and differentiation visualized by electron microscopy. Cell properties maintained after short-term storage (2–3 days at 4° C) included: (i) properties of voltage-dependent ionic channels tested by patch-clamp electrophysiological techniques; (ii) expression of cell-adhesion membrane proteins tested by immunohistochemistry (iii) morphological differentiation obtained by depletion of foetal calf serum in culture medium. The advantages of such an immobilization technique as applied to neurone cells are discussed. Offprint requests to: M. Simonneau     

Immobilization of Bacillus amyloliquefaciens MBL27 cells for enhanced antimicrobial protein production using calcium alginate beads

Cell immobilization is one of the common techniques for increasing the overall cell concentration and productivity. Bacillus amyloliquefaciens MBL27 cells were immobilized in calcium alginate beads and it is a promising method for repeated AMP (antimicrobial protein) production. The present study aimed at determining the optimal conditions for immobilization of B. amyloliquefaciens MBL27 cells in calcium alginate beads and the operational stability for enhanced production of the AMP. AMP production with free and immobilized cells was also done. In batch fermentation, maximum AMP production (7300 AU (arbitrary units)/ml against Staphylococcus aureus) was obtained with immobilized cells in shake flasks under optimized parameters such as 3% (w/v) sodium alginate, 136?mM CaCl2 with 350 alginate beads/flask of 2.7-3.0?mm diameter. In repeated cultivation, the highest activity was obtained after the second cycle of use and approx. 94% production was noted up to the fifth cycle. The immobilized cells of B. amyloliquefaciens MBL27 in alginate beads are more efficient for the production of AMP and had good stability. The potential application of AMP as a wound healant and the need for development of economical methods for improved production make whole cell immobilization an excellent alternative method for enhanced AMP production.     

Immobilization of Lactobacillus rhamnosus in polyvinyl alcohol/calcium alginate matrix for production of lactic acid

Immobilization of Lactobacillus rhamnosus ATCC7469 in poly(vinyl alcohol)/calcium alginate (PVA/Ca-alginate) matrix using “freezing–thawing” technique for application in lactic acid (LA) fermentation was studied in this paper. PVA/Ca-alginate beads were made from sterile and non-sterile PVA and sodium alginate solutions. According to mechanical properties, the PVA/Ca-alginate beads expressed a strong elastic character. Obtained PVA/Ca-alginate beads were further applied in batch and repeated batch LA fermentations. Regarding cell viability, L. rhamnosus cells survived well rather sharp immobilization procedure and significant cell proliferation was observed in further fermentation studies achieving high cell viability (up to 10.7 log CFU g⁻¹) in sterile beads. In batch LA fermentation, the immobilized biocatalyst was superior to free cell fermentation system (by 37.1%), while the highest LA yield and volumetric productivity of 97.6% and 0.8 g L⁻¹ h⁻¹, respectively, were attained in repeated batch fermentation. During seven consecutive batch fermentations, the biocatalyst showed high mechanical and operational stability reaching an overall productivity of 0.78 g L⁻¹ h⁻¹. This study suggested that the “freezing–thawing” technique can be successfully used for immobilization of L. rhamnosus in PVA/Ca-alginate matrix without loss of either viability or LA fermentation capability.

     

Affinity binding of cells to cryogel adsorbents with immobilized specific ligands: effect of ligand coupling and matrix architecture

The capture of human acute myeloid leukemia KG-1 cells expressing the CD34 surface antigen and the fractionation of human blood lymphocytes were evaluated on polyvinyl alcohol (PVA)-cryogel beads and dimethyl acrylamide (DMAAm) monolithic cryogel with immobilized protein A. The affinity ligand (protein A) was chemically coupled to the reactive PVA-cryogel beads and epoxy-derivatized monolithic cryogels through different immobilization techniques and the binding efficiency of the cell surface receptors specific antibody-labeled cells to the gels/beads was determined. The binding of cells to monolithic cryogel was higher (90-95%) compared with cryogel beads (76%). B-lymphocytes, which bound to the protein A-cryogel beads, were separated from T-lymphocytes with yields for the two cell types 74 and 85%, respectively. About 91% of the bound B-cells could be recovered without significantly impairing their viability. Our results show differences in the percentage of cell-binding to the immunosorbents caused by ligand density, flow shear forces and bond strength between the cells and the affinity surface once distinct chemical coupling of protein A, size of beads, sequence of antibody binding to protein A adsorbents, morphology and geometry of surface matrices were compared.     

Culture and nitrite uptake in immobilized Scenedesmus obliquus

Summary The green alga Scenedesmus obliquus was immobilized in Ca-alginate beads. The cell growth after immobilization was studied by cell counting. The nitrite uptake was not affected by immobilization, except that a longer lag phase was observed in immobilized cells than in free ones. That result could be due to a barrier effect of the matrix against nitrite diffusion inside the beads. The treatment of cells by glycerol prior to their immobilization in a batch reactor induced an increase of nitrite uptake by the cells. This effect disappeared after a few runs. The glycerol effect on specific rates seemed also to decrease when the number of immobilized cells increased. This decrease can be related to the decrease of light efficiency as well as substrate accessibility when a high cell concentration was used. Several alternating runs of Tris-HCl buffer containing nitrite growth medium depleted in combined nitrogen were tested. Cellular growth occurred inside the beads up to a maximum followed by a decrease of cell number in the beads.     

Production of molecular hydrogen with immobilized cells ofRhodospirillum rubrum

Summary Cells ofRhodospirillum rubrum have been immobilized in various gels and tested for photobiological hydrogen production. Agar proved to be the best immobilizing agent with respect to production rates as well as stability. Agar immobilized cells were also superior compared to liquid suspension cultures. Growth conditions of the cells prior to immobilization, e.g. cell age, light intensity or nutrient composition, were of primary importance for the activity in the later immobilized state. A reactor with agar immobilized cells has been operated successfully over 3000 h with a loss of the activity of about 60%. Mean rates for hydrogen production for immobilized cells in this work during the first 60 to 70 hours after immobilization were in the range of 18 to 34 μl H₂ mg⁻¹ d.w. h⁻¹ and thus by a factor of up to 2 higher than liquid cultures under the same conditions. Maximal rates of hydrogen production (57 μl H₂ ml⁻¹ immobilized cell suspension) were reached in agar gel beads with cells immobilized after 70 h growth in liquid culture in the light and a cell density of 1.0 mg ml⁻¹, 70 h after immobilization.     

Vero细胞微载体培养的化学成分明确无血清培养基的设计

目的：设计适用于Vero细胞微载体培养的化学成分明确无血清培养基。方法：以商品化的DMEM／F12合成培养基为基础培养基,应用Plackett—Burman实验设计和响应面分析法设计支持Vero细胞微载体培养的化学成分明确无血清培养基。结果：以细胞密度为评价指标,在单因素实验的基础上采用Plackett-Burman实验设计考察10种培养基添加成分对Vero细胞生长的影响,确定了3种对Vero细胞生长起明显促进作用的培养基添加成分,为胰岛素、血清素和腐胺。继而利用响应面法分析了这3种添加成分的最佳水平范围,设计了一种支持Vero细胞贴附培养的无血清培养基（VERO—SFM—A）。在Bellco搅拌式培养瓶中采用VERO-SFM．A和Cytodex1微载体培养Vero细胞,细胞密度由接种时的4×10^5cells／ml增加到培养6d后的22．3×10^cells／ml,细胞活力保持在96％以上。结论：VERO—SFM—A能够有效地支持Vero细胞在微载体表面固定化生长并达到较高的细胞密度,具有实际应用于Vero细胞微载体规模化培养的应用潜力。     

Nitrate and phosphate removal by chitosan immobilized Scenedesmus

The effect of chitosan immobilization of Scenedesmus spp. cells on its viability, growth and nitrate and phosphate uptake was investigated. Scenedesmus sp. (strains 1 and 2) and Scenedesmus obliquus immobilized in chitosan beads showed high viability after the immobilization process. Immobilized Scenedesmus sp. strain 1 had a higher growth rate than its free living counterpart. Nitrate and phosphate uptake by immobilized cells of Scenedesmus sp. (strain 1), freely suspended cells and blank chitosan beads (without cells) were evaluated. Immobilized cells accomplished a 70% nitrate and 94% phosphate removal within 12h of incubation while free-living cells removed 20% nitrate and 30% phosphate within 36 h of treatment. Blank chitosan beads were responsible for up to 20% nitrate and 60% phosphate uptake at the end of the experiment. Chitosan is a suitable matrix for immobilization of microalgae, particularly Scenedesmus sp., but this system should be improved before its application for water quality control.     

Characterization of kappa-carrageenan gels used for immobilization of Bacillus firmus.

In this study, aimed at a biochemical and physical characterization of kappa-carrageenan gels used for entrapment of Bacillus firmus NRS 783 (a superior producer of an alkaline protease), effects of carrageenan concentration, gelation temperature, initial cell loading, and strength of the curing agent (KCl) on the properties of cell-free and cell-laden gels were examined. The physical properties of the differently prepared gels that were examined included density, free volume fraction, mechanical strength, and change in gel volume during gel curing. The biochemical characteristics studied included viability of gel-entrapped cells, cell leakage from cell-laden gels, and cell penetration into cell-free gels. For the range of carrageenan contents investigated [between 2% and 5% (w/v)], the mechanical strength of the gels with/without KCl curing was observed to increase with an increase in carrageenan content of gels. The mechanical strength of each gel increased substantially upon extensive curing. Free volume fractions in excess of 0.8 were observed for all gels. Of cells that were viable prior to immobilization, 90-92% remained viable after formation and extensive curing of gels for cell-gel mixtures prepared at 45 degrees C. Attempts at prolonged storage of cell-laden gel beads at 0 degrees C as stock cultures of immobilized B. firmus were unsuccessful due to a significant decline in cell viability during such storage. On the basis of the cell leakage studies, the average pore sizes of 2%, 3%, 4%, and 5% gels were deduced to increase in the following order of carrageenan content (w/v): 4%, 3%, 2%, and 5%. Commensurate with the decrease in the average pore size (or the increased tightness of the gels) with increasing carrageenan content, both the extent of cell leakage and the extent of net cell penetration decreased with increasing carrageenan content for the first three gels. Owing to non-uniform distribution of free space and much larger pores, the extent of net cell penetration in 5% carrageenan gels was considerably low, while the extent of cell leakage in 5% carrageenan gels was an order of magnitude greater than the extents of cell leakage in the other three gels.