Barium Alginate Beads Research Articles

Biotransformation of aromatic compounds by immobilized bacterial strains in barium alginate beads

In the present study, we have investigated the biotransformation of different aromatic compounds to their cis-dihydrodiols ( cis-diols) with immobilized Pseudomonas putida UV4 cells using barium alginate as the immobilization medium for the cells in a fluidized-bed reactor. The reactions have been performed in a biphasic system containing 20% (v/v) tetradecane. The bacterial beads were fluidized using a flow of pure oxygen at a flow rate of 100 ml min −1. The production of toluene cis-diol under the same conditions by the recombinant organism Escherichia coli JM109 (pKST11) was compared. The production of toluene cis-diol with E. coli JM109 (pKST11) was more than 24 times higher that the values reported in the literature using similar recombinant non-immobilized organisms. The capacity of immobilized E. coli JM109 (pKST11) to yield cis-diols from different aromatic substrates in small-scale biotransformations was also investigated.

Production of toluene cis-diol by immobilized pseudomonas putida UV4 cells in barium alginate beads

In the present study, we have investigated the biotransformation of toluene to its cis-dihydrodiol ( cis-diol) with immobilized Pseudomonas putida UV4 cells using different conditions of immobilization with a view to improving its production. The choice of alginate and its concentration for the immobilization of the cells were found to be the most important factors affecting the production of toluene cis-diol. The concentration of minerals and oxygen in the reaction medium and the methodology of substrate addition were investigated and the optimal conditions were defined. Once the optimal conditions for biotransformations and entrapment were determined, a packed-bed and fluidized-bed reactor were evaluated for the biotransformation process. The results using air as the gas supply showed an increase in the total production from 0.15 mol cis-diol · g −1 dry cell weight (dcw) in the packed-bed reactor to 0.28 mol cis-diol · g −1 dcw in the fluidized-bed reactor. When pure oxygen was used in place of air in the fluidized-bed reactor, a dramatic increase in total production up to a maximum of 6.1 mol cis-diol · g −1 dcw using a medium flow rate of 100 ml min −1 was achieved. Under optimal conditions, a maximum rate of production of 86.9 mmol cis-diol g −1 dcw h −1 was achieved for 48 h. This was seven times higher than the rate previously reported in the literature and for a much longer period of time; consequently, the overall production observed was more than 75 times higher than the values reported in the literature.

Evaluation of Bacteriocin Activity Produced in Milk by Lactococcus lactis, Subspecies lactis, Immobilized in Barium Alginate Beadsa

Evaluation of Bacteriocin Activity Produced in Milk by <i>Lactococcus lactis</i>, Subspecies <i>lactis</i>, Immobilized in Barium Alginate Beads^a

Evaluation of new small barium alginate microcapsules

Microencapsulation of islets of Langerhans has been proposed in order to prevent immune rejection and possible recurrence of autoimmune disease. This study introduces a fast simple one-step microencapsulation procedure which allows the production of small sized barium-alginate beads. The volume of the microcapsules produced was approximately that of the encapsulated islets. Consequently, the insulin kinetics and the oxygen diffusion were favoured, while the transplanted tissue volume was reduced. Electron microscopy and immunoisolating testing were performed to evaluate the molecular cut-off, the physical and chemical characteristics of these microcapsules. Immunohistochemical staining and perifusion experiments of microencapsulated pancreatic islets showed their viability after the encapsulation procedure as well as in vivo experiments. In fact, microencapsulated porcine islets were implanted intraperitoneally into streptozotocin-diabetic rats. The xenografts reversed the hyperglycemic state and functioned for a period ranging from 9 to 385 days. The low mannuronic acid concentration and the purity grade of the alginate, exerted a combined influence on the capsule biocompatibility as in vivo studies showed.

Bioconversion of acrylonitrile into acrylamide using a highly compact multiphasic reactor

Acrylamide production from acrylonitrile has been carried out in a specially designed fluidized bed reactor using immobilized cells of Brevibacterium sp. A4. The cells were entrapped in modified barium alginate beads. The optimum conditions with regard to catalyst stability were determined as: pH, 7.5; temperature, 5 °C; maximum acrylamide concentration, 60 g l −1. There was no diffusional limitation due to the gel. On line determinations of the kinetic constants were performed. A high value of the maximum hydration rate was found but, the Michaelis-Menten constant for acrylonitrile, K m, and the inhibition constant for acrylamide, K i, appeared to be higher than the values obtained for free enzyme. The volumetric productivity of the reactor varied with both the substrate concentration and the feed rate.

Photophosphorylation in bacterial chromatophores entrapped in alginate gel: Improvement of the physical and biochemical properties of gel beads with barium as gel-inducing agent

The immobilization of Rhodopseudomonas capsulata chromatophores by entrapment in an alginate gel is described. Alginate beads were prepared with Ba 2+, Sr 2+ and Ca 2+ as gel-forming agents and compared for their mechanical strength, chemical resistance against disruption by phosphate-induced swelling, and yield of photophosphorylation activity. Barium alginate beads proved to have better physico-chemical properties than the more commonly used calcium alginate beads. After embedding in barium alginate gel, R. capsulata chromatophores retained a high yield (up to 70%) of their photophosphorylation capacity. Alginate entrapment did not cause a large increase in the Michaelis constant for ADP and phosphate, the substrates of adenosinetriphosphatase (ATPase). These constants were K ADP m = 1.4 × 10 −5 m and K P i m = 2.2 × 10 −4 m for free chromatophores and K ADP m = 2.3 × 10 −4 m and K P i m = 5.6 × 10 −4 m for chromatophores entrapped in barium alginate gel. However, embedding gave no additional protection against rapid inactivation of chromatophores upon storage at 3°C. Preliminary results with a batch reactor for continuous ATP regeneration are presented. The barium alginate method has two features which are not generally encountered at the same time, extremely mild conditions for entrapment and excellent physical properties of the gels beads, which make this method a suitable tool for the construction of bioreactors with immobilized cells or organelles.