Survival ofalginate-ecapsulated Pseudomonas fluorescens cells in soil

Alginate-encapsulated and unencapsulated cells of Pseudomonas fluorescens Rsf were introduced into soil microcosms with and without wheat plants to evaluate bacterial survival and colonization of the rhizoplane and rhizosphere. Encapsualtion of cells in alginate amended with skim milk or with skim milk plus bentonite clay significantly enchanced long-term survival of the cells. There was a negligible effect on long-term bacterial survival when cells were encapsulated in alginate amended with TY medium or soil extract, as compared to water. Drying of beads resulted in a significant reduction in bacterial viability. After addition to soil, cells in dried beads increased in numbers and exhibited stable population densities, whereas cells added in moist beads showed stable dynamics at a higher level. Cells encapsulated in dried beads or fresh beads survived better than unencapsulated cells added to soil. Both cells in moist and dried alginate beads also survide a dry/wet cycle in soil, whereas unencapsulated cells were sensitive to these moisture fluctuations. Shortly after inoculation and 63 days after this, cells from moist beads colonized wheat roots at significantly higher levels than unencapsulated cells, whereas cells in dried beads did so at levels similat to unencapsulated cells. Cells in beads initially placed at different distance from developing root mat were able to move towards and colonize the rhizosphere, at levels of roughly 10⁴ to 10⁶ colony-forming units fo P. fluorescens R2f per gram of dry soil. Correspondence to: J. T. Trevors or J. D. van Elsas     

Development of a microchannel emulsification process for pancreatic beta cell encapsulation

In this study, we developed a high-throughput microchannel emulsification process to encapsulate pancreatic beta cells in monodisperse alginate beads. The process builds on a stirred emulsification and internal gelation method previously adapted to pancreatic cell encapsulation. Alginate bead production was achieved by flowing a 0.5–2.5% alginate solution with cells and CaCO₃ across a 1-mm thick polytetrafluoroethylene plate with 700 × 200 μm rectangular straight-through channels. Alginate beads ranging from 1.5–3 mm in diameter were obtained at production rates exceeding 140 mL/hr per microchannel. Compared to the stirred emulsification process, the microchannel emulsification beads had a narrower size distribution and demonstrated enhanced compressive burst strength. Both microchannel and stirred emulsification beads exhibited homogeneous profiles of 0.7% alginate concentration using an initial alginate solution concentration of 1.5%. Encapsulated beta cell viability of 89 ± 2% based on live/dead staining was achieved by minimizing the bead residence time in the acidified organic phase fluid. Microchannel emulsification is a promising method for clinical-scale pancreatic beta cell encapsulation as well as other applications in the pharmaceutical, food, and cosmetic industries.     

The effect of calcium alginate entrapment on the physiology of Mycobacterium sp. strain E3

The influence of calcium alginate entrapment on the physiology of Mycobacterium sp. E3 is reported. As a model system the NADH-requiring conversion of propene to 1,2-epoxypropane in the presence and absence of glucose as co-substrate was selected. The co-factor-dependent reaction was used as a measure of the physiological status of the resting cells. Initial kinetic experiments established a system free from diffusional limitations. In the presence of glucose there were no differences between the physiology of the free and immobilized cells. The apparent differences observed in the absence of co-substrate were demonstrated to be caused by calcium ions and to a lesser degree alginate; the addition of calcium, alginate or calcium alginate beads containing no cells to the free cells gave similar data to that obtained with immobilized cells. The results presented highlight the high concentrations of calcium to which cells immobilized in calcium alginate beads can be exposed. Correspondence to: M. R. Smith     

Cryopreservation of hairy root cultures of Vinca minor (L.) by encapsulation-dehydration

Hairy root cultures of Vinca minor and Ajuga reptans var. atropurpurea could be cryopreserved when the roots were precultured and encapsulated in 2% (w/v) alginate beads with 0.3 M sucrose and 0.5 M glycerol and dehydrated until the bead weight reached 25% of the initial weight before cooling in liquid nitrogen. Preculture and encapsulation of the roots with abscisic acid was effective in increasing the survival rates. For V. minor root tips moreover a sufficiently high survival rate of more than 70% was attained by eliminating glycerol from the preculture medium and dehydration of beads until 23% of the initial weight was reached instead of 25%.     

Alginate beads as a storage, delivery and containment system for genetically modified PCB degrader and PCB biosensor derivatives of Pseudomonas fluorescens F113

Aims: Pseudomonas fluorescens F113Rifpcb is a genetically engineered rhizosphere bacterium with the potential to degrade polychlorinated biphenyls (PCBs). F113Rifpcbgfp and F113L::1180gfp are biosensor strains capable of detecting PCB bioavailability and biodegradation. The aim of this paper is to evaluate the use of alginate beads as a storage, delivery and containment system for use of these strains in PCB contaminated soils. Methods and Results: The survival and release of Ps. fluorescens F113Rifpcb from alginate beads were evaluated. Two Ps. fluorescens F113‐based biosensor strains were encapsulated, and their ability to detect 3‐chlorobenzoate (3‐CBA) and 3‐chlorobiphenyl (3‐CBP) degradation in soil was assessed. After 250 days of storage, 100% recovery of viable F113Rifpcb cells was possible. Amendments to the alginate formulation allowed for the timed release of the inoculant. Encapsulation of the F113Rifpcb cells provided a more targeted approach for the inoculation of plants and resulted in lower inoculum populations in the bulk soil, which may reduce the risk of unintentional spread of these genetically modified micro‐organisms in the environment. Encapsulation of the biosensor strains in alginate beads did not interfere with their ability to detect either 3‐CBA or 3‐CBP degradation. In fact, detection of 3‐CBP degradation was enhanced in encapsulated biosensors. Conclusions: Alginate beads are an effective storage and delivery system for PCB degrading inocula and biosensors. Significance and Impact of the Study: Pseudomonas fluorescens F113Rifpcb and the F113 derivative PCB biosensor strains have excellent potential for detecting and bioremediation of PCB contaminated soils. The alginate bead delivery system could facilitate the application of these strains as biosensors.     

Nutrient-enhanced survival of and phenanthrene mineralization by alginate-encapsulated and freePseudomonas sp. UG14Lr cells in creosote-contaminated soil slurries

The effects of nutrient amendment and alginate encapsulation on survival of and phenanthrene mineralization by the bioluminescentPseudomonas sp. UG14Lr in creosote-contaminated soil slurries were examined. UG14Lr was inoculated into creosote-contaminated soil slurries either as a free cell suspension or encapsulated in alginate beads prepared with montmorillonite clay and skim milk. Additional treatments were free-cell-inoculated slurries amended with sterile alginate beads, free-cell-inoculated and uninoculated slurries amended with skim milk only, and uninoculated, unamended slurries. Mineralization was determined by measuring¹⁴CO₂ released from radiolabelled phenanthrene. Survival was measured by selective plating and bioluminescence. Inclusion of skim milk was found to enhance both survival of and phenanthrene mineralization by free and encapsulated UG14Lr cells.     

Successful cryopreservation of suspension cells by encapsulation-dehydration

Cryopreservation of a Catharanthus cell suspension was performed after encapsulation in alginate beads. Encapsulated cells were precultured in sucrose-enriched medium for several days, dried over silica gel, and directly cooled in liquid nitrogen. After rewarming in air at room temperature, alginate beads were placed on semi-solid culture medium. Following regrowth, beads transferred to liquid medium generated a new cell suspension. Cell survival and regrowth from cryopreserved encapsulated cells depended on preculture duration and residual water content after air-drying.Jean Dereuddre unexpectedly passed away on 16 February 1995.     

Preservation of chitinolytic Pantoae agglomerans in a viable form by cellular dried alginate-based carriers

Improved viability of Gram-negative bacteria during freeze-dehydration, storage, and soil inoculation is of crucial importance to their efficient application. The chitinolytic Pantoae (Enterobacter) agglomerans strain IC1270, a potential biocontrol agent of soil-borne plant-pathogenic fungi, was used as a model organism to study the efficacy of freeze-dried alginate-based beads (macrocapsules) as possible carriers for immobilized Gram-negative bacterial cells. These macrocapsules were produced by freeze-dehydration of alginate gel spherical beads, in which different amounts of bacteria, glycerol, and colloidal chitin were entrapped. Subsequent drying produced different unexpected structures, pore-size distributions, and changes in the outer and inner appearance of the resultant dried cellular solid. With increasing glycerol content, the proportion of larger pores increased. These structures can be related to changes in the slow-release properties of the dried beads. The amount of glycerol in the beads differed from that in the alginate solution as a result of leakage during the beads' preparation and dehydration. Entrapping 10(9) cells per bead produced from alginate solution containing 30% glycerol and 1% chitin resulted in improved (in comparison to other studies) survival prospects (95%) during freeze-drying. Moreover, immobilization of the bacterium sharply improved its survival in nonsterile irrigated and dry soils compared to bacteria in a water suspension. The results suggest that optimized conservation of Gram-negative bacteria in dry glycerol-containing alginate-based cellular solids is not only possible but applicable for a variety of uses.     

A comparative study on the production of amidase using immobilized and dehydrated immobilized cells of Pseudomonas putida MTCC 6809

Pseudomonas putida MTCC 6809, a plant growth promoting rhizobacteria producing amidase was isolated from the rhizosphere of Pisum sativum. The cells were immobilized in sodium alginate for the production of amidase and the effect of dehydration on immobilized beads were studied. Optimization of process parameters for amidase production was carried out to enhance enzyme production using immobilized cells. From the results it is clear that 2% and 3% (w/v) of alginate were suitable for amidase production with 12.8 and 13 U/ml activity, respectively after 36 h of incubation. Among the various substrates studied acetamide (2% w/v) was a good inducer of amidase. It was observed that immobilized catalysts could be recycled up to five batches. Amidase production was observed in both free and immobilized cells, nevertheless immobilization is much favored in comparison to free cells, as it leads to reusability of beads, lesser contamination, consistent amidase production and adaptability to wide range of culture conditions. The relative enzyme activity with the dehydrated beads was only 27% in comparison to hydrated beads, it is possible to pack considerably more into a fixed volume as the relative volume of dehydrated beads is 20%. Even though consistent amidase production was difficult to achieve using dehydrated beads, which may have certain advantages like less chances for microbial contamination and easy to transport.     

Encapsulation of Ketoprofen and Ketoprofen Lysinate by Prilling for Controlled Drug Release

In this paper, ketoprofen and ketoprofen lysinate were used as model drugs in order to investigate release profiles of poorly soluble and very soluble drug from sodium alginate beads manufactured by prilling. The effect of polymer concentration, viscosity, and drug/polymer ratio on bead micromeritics and drug release rate was studied. Ketoprofen and ketoprofen lysinate loaded alginate beads were obtained in a very narrow dimensional range when the Cross model was used to set prilling operative conditions. Size distribution of alginate beads in the hydrated state was strongly dependent on viscosity of drug/polymer solutions and frequency of the vibration. The release kinetics of the drugs showed that drug release rate was related with alginate concentration and solubility of the drug. Alginate solutions with concentration higher than 0.50% (w/w) were suitable to prepare ketoprofen gastro-resistant formulation, while for ketoprofen lysinate alginate, concentration should be increased to 1.50% (w/w) in order to retain the drug in gastric environment. Differential scanning calorimetry thermograms and Fourier transform infrared analyses of drug-loaded alginate beads indicated complex chemical interactions between carboxyl groups of the drug and polymer matrix in drug-loaded beads that contribute to the differences in release profile between ketoprofen and ketoprofen lysinate. Total release of the drugs in intestinal medium was dependent on the solubility of the drug and was achieved between 4 and 6 h.     

Immobilization of recombinant nanobiofiber CS3 fimbriae onto alginate beads for improvement of cadmium biosorption

A cell surface display system with metalbinding properties was previously developed using CS3 fimbriae, which are hollow tubes 20 nm-thick and 2 nm in diameter. In this study, hybrid CS3 pili were separated from recombinant Escherichia coli and entrapped in calcium alginate gel beads in order to improve their stabilization and also adsorption of heavy metals. The surface morphology of the gel beads containing pili was investigated by scanning electron microscopy (SEM). Immunofluorescence microscopy was employed to confirm the attachment of nanobiofibers to the alginate beads. The effects of three variables (sodium alginate concentration, protein to alginate mass ratio, and bead size) at two levels each on Cd²⁺ biosorption efficiency were investigated by full factorial experimental design. A second-order polynomial equation modeled the design space for the process response of cadmium removal capacity. The optimal values of the factors were obtained as follows: 1% sodium alginate concentration, 0.25 protein to alginate mass ratio, and a 6 mm bead size. Under these conditions, Cd²⁺ was adsorbed at 45.45 mg/g to the nanobiofiber. The results indicate that the immobilized recombinant hybrid CS3 pili may be an appropriate biosorbent for removal of heavy metals from polluted aquatic environments.     

Continuous penicillin production by Penicillium chrysogenum immobilized in calcium alginate beads

Summary A high penicillin-producing Penicillium chrysogenum strain immobilized in calcium alginate beads was used for continuous penicillin fermentation in a bubble column and in a conical bubble fermentor. The fermentation was limited by the growth rate, dilution rates and the stability of the alginate beads. The immobilized cells lost their ability to produce penicillin in the bubble column after 48 h from beginning of the continuous fermentation. In the conical bubble fermentor the immobilized cells remained active for more than 7 days. This bioreactor ensured a good distribution of nutrients and oxygen as well as a higher mechanical stability of the alginate beads.     

Survival of Bifidobacterium longum Immobilized in Calcium Alginate Beads in Simulated Gastric Juices and Bile Salt Solution

Bifidobacterium longum KCTC 3128 and HLC 3742 were independently immobilized (entrapped) in calcium alginate beads containing 2, 3, and 4% sodium alginate. When the bifidobacteria entrapped in calcium alginate beads were exposed to simulated gastric juices and a bile salt solution, the death rate of the cells in the beads decreased proportionally with an increase in both the alginate gel concentration and bead size. The initial cell numbers in the beads affected the numbers of survivors after exposure to these solutions; however, the death rates of the viable cells were not affected. Accordingly, a mathematical model was formulated which expressed the influences of several parameters (gel concentration, bead size, and initial cell numbers) on the survival of entrapped bifidobacteria after sequential exposure to simulated gastric juices followed by a bile salt solution. The model proposed in this paper may be useful for estimating the survival of bifidobacteria in beads and establishing optimal entrapment conditions.     

A novel encapsulation technique for the production of artificial seeds

A novel technique for the encapsulation of plant material in calcium alginate hollow beads was tested. The technique involves suspending plant material (i.e. plant cells, tissues, organs, shoot tips, somatic embryos) in a solution containing carboxymethylcellulose and calcium chloride and then dripping it into a stirred sodium alginate solution. In initial experiments with Daucus carota (carrot), it was found that after 14 days of cultivation, 100 % of seeds encapsulated in calcium alginate hollow beads would germinate in the liquid core and that 13% would burst the capsules. Embryogenic calli developed inside hollow beads and formed somatic embryos while calli in conventional calcium alginate beads became detached from the beads early in development, and no somatic embryogenesis occurred. With Solanum tuberosum (potato), development of calli was observed in 50% of hollow beads. Eighty-one percent of shoot tips encapsulated in hollow beads sprouted and grew out of the capsules. Received: 28 October 1999 / Revision received: 11 February 2000 / Accepted: 22 February 2000     

Use of immobilized cells of the strainCorynebacterium sp. for 4-nitrophenol degradation

4-Nitrophenol degrading bacterial strainCorynebacterium sp. 8/3 was isolated from chemically polluted soil. The product of cometabolic transformation of 4-nitrophenol was identified as 4-nitrocatechol., Effect of immobilization (encapsulation in calcium alginate) ofCorynebacterium sp. cells on the process of 4-nitrophenol transformation was investigated. 4-Nitrophenol was converted by encapsulated cells and encapsulation had a protective effect, on 4-nitrophenol degrading bacteria in repeated cycles of incubation. Transformation of 4-nitrophenol to 4-nitrocatechol by encapsulated cells was influenced by pH of medium but was not influenced by concentration of alginate and CaCl₂. The count of viable cells in alginate beads declined approximately by one order of magnitude after 10 d of incubation. Presented at the 4th Mini-Symposium on Biosorption and Microbial Degradation, Prague, Czech Republic, November 26–29, 1996.     

Preservation methods of <Emphasis Type="Italic">Tolypothrix tenuis</Emphasis> for use as a cyanobacterial fertilizer

The suitability of the cyanobacterium Tolypothrix tenuis as a potential biofertilizer was evaluated by measuring cell viability in stored samples preserved by various methods, including freezing at −20°C, freeze-drying, desiccation as flakes and immobilization in alginate beads. The viability recovery and the retained viability index (RVI₁₀) were used as indicators of cell survival after 3 and 15 months storage. The highest recovery level (85%) was obtained by freeze-drying using skimmed milk as the resuspension solution for long-term storage. Dried alginate beads showed a better cell survival (RVI₁₀ 0.25) than air-dried flakes (RVI₁₀ −0.63) after 15 months storage. However, desiccated flakes previously treated with Ca²⁺ and Mg²⁺ ions improved cell survival capacity at the longest period assayed (RVI₁₀ 0.08), extending cell viability by 9 months compared to dried-powder material.     

Entrapment of biological control agents applied to entomopathogenic nematodes

Summary Hydrogels of alginate, phospho guar gum, carboxymethyl guar gum, k-carrageenan and cellulose sulphate, respectively were tested to find easily redissolvable gels. The entomopathogenic nematode, Heterorhabditis sp., was entrapped in calcium alginate beads, calcium alginate hollow spheres and foils made from different hydrogels. Emigration from calcium alginate beads after 7 days of storage was 100 % at room temperature and was lowered to 6 % at 6 °C, whereas no emigration from calcium alginate hollow spheres was found at either temperature. Highly concentrated polymer foils produced on gauze showed reduced emigration with a survival of 80 % after 24 h compared to foils produced on glass slides. Calcium alginate beads can be used for a controlled release of the nematode into the environment, while hollow spheres and foils are suitable for storage.Dedicated to Prof. Dr. F. Wagner on the occasion of his 65th birthday     

Performance of immobilized cells for dihexyl sulfosuccinate biotransformation

Possibilities of using immobilized bacterial cells for waste water treatment in a continuous process was determined. Cells ofComamonas terrigena strain N3H immobilized in calcium alginate beads were successful by used in packed bead-type reactor for continuous biotransformation of the anion-active surfactant dihexyl sulfosuccinate. Absence of calcium ions from the treated medium led to the disruption of alginate beads within 8 d of usage. When the medium was supplemented with Ca²⁺ ions the beads were stable for at least one month in the continuous process. During the whole time period the transformation effectivity was in the range of 80–100% even at the highest, flow rate of 14 mL/min. Presented at the 4th Mini-Symposium on Biosorption and Microbial Degradation, Prague, Czech Republic, November 26–29, 1996.     

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.     

Mixed photo-cross-linked polyvinyl alcohol and calcium-alginate gels for cell entrapment

Living cells may be immobilized by gel entrapment under very mild conditions. The ionotropic gelation of alginate with bivalent cations such as Ca²⁺, as well as photo-induced gelation of polyvinyl alcohol (PVA) bearing photosensitive stilbazolium (SbQ) groups, are procedures that are compatible with most bioactive materials. In the search for more stable and stronger alginate gel beads, experiments have been carried out to investigate mixed gels from alginate and PVA-SbQ. The swelling capacities, diffusion properties, and potential toxic effect of the binary gel beads have been evaluated. The gel beads of selected PVA-SbQ/alginate mixtures were applied successfully as carriers in a denitrification process with continuous feeding of unsterilized water medium. Under such conditions, the purely synthetic PVA-SbQ network is expected to have a longer lifespan than a natural biopolymer such as alginate.