Alginate beads

A rapid activity loss (a few days) was observed with whole cells. Immobilisation increased the stability and continuous production of L-phenylalanine was possible using alginate bead immobilised cells of P. fluorescerts for 60 days. However, to achieve this the cofactor pyridoxalphosphate had to be continuously added to the beads to correct for the dissociation of the cofactor and loss from the cells. 

In fermentation for the production of acetic acid, ethyl alcohol is used in an aerobic process. In an ethanol oxidation process, the biocatalyst Acetobacter aceti was used to convert ethanol to acetic acid under aerobic conditions. A continuous fermentation for vinegar production was proposed for utilisation of non-viable A. aceti immobilised on the surface of alginate beads. 

Microcapsules can be used for mammalian cell culture and the controlled release of drugs, vaccines, antibiotics and hormones. To prevent the loss of encapsulated materials, the microcapsules should be coated with another polymer that forms a membrane at the bead surface. The most well-known system is the encapsulation of the alginate beads with poly-L-lysine. 

Lactic acid bacteria were immobilized in Ca-alginate beads prepared from different concentration of Na-alginate (1.0%, 2.0%, 4.0%, 6.0% and 8.0% w/v) and their fermentation efficiencies were investigated in liquid pineapple waste containing 31.3 gL of glucose... 

Buthe, A., Hartmeier, W., and Ansorge-Schnmacher, M.B., Novel solvent-based method for preparation of alginate beads with improved roundness and predictable size, J. Microencapsulation, 21, 865, 2004. 

The resulting enzyme-containing microcapsules (which can contain different enzymes in different capsules, as was the case here) were then embedded within a Ca-alginate bead, designated a capsules-in-bead structured microreactor (Scheme 5.7). 

D-Pantolactone and L-pantolactone are used as chiral intermediates in chemical synthesis, whereas pantoic acid is used as a vitamin B2 complex. All can be obtained from racemic mixtures by consecutive enzymatic hydrolysis and extraction. Subsequently, the desired hydrolysed enantiomer is lactonized, extracted and crystallized (Figure 4.6). The nondesired enantiomer is reracemized and recycled into the plug-flow reactor [33,34]. Herewith, a conversion of 90-95% is reached, meaning that the resolution of racemic mixtures is an alternative to a possible chiral synthesis. The applied y-lactonase from Fusarium oxysporum in the form of resting whole cells immobilized in calcium alginate beads retains more than 90% of its initial activity even after 180 days of continuous use. The biotransformation yielding D-pantolactone in a fixed-bed reactor skips several steps here that are necessary in the chemical resolution. Hence, the illustrated process carried out by Fuji Chemical Industries Co., Ltd is an elegant way for resolution of racemic mixtures. 

Corynebacterium glutamicum (CGMCC No. 1464) cells immobilized in calcium alginate beads cross-linked with polyethenimine and glutaraldehyde have been employed for the production of nicotinamide from 3-cyanopyridine [21], The reaction was mn at 10-15 °C,... 

A thermally stable NHase from Comamonas testosteroni 5-MGAM-4D (ATCC 55 744) [22] was recombinantly expressed in Escherichia coli, and the resulting transformant cells immobilized in alginate beads that were subsequently chemically cross-linked with glutaraldehyde and polyethylenimine. This immobilized cell catalyst (at 0.5 % dew per reaction volume) was added to an aqueous reaction mixture containing 32wt% 3-cyanopyridine at 25 °C, and a quantitative conversion to nicotinamide was obtained. The versatility of this catalyst system was further illustrated by a systematic study of substrates, which included... 

A procedure for immobilization of a P. stutzeri UP-1 strain using sodium alginate was reported [133], This strain does not perform sulfur-specific desulfurization, but degrades DBT via the Kodama pathway. Nevertheless, the report discussed immobilization of the biocatalyst cells in alginate beads with successful biocatalyst recovery and regeneration for a period of 600 h. However, the immobilized biocatalyst did decrease in specific activity, although the extent of loss was not discussed. The biocatalyst was separated after every 100 h of treatment, washed with saline and a boric acid solution and reused in subsequent experiment. The non-immobilized cells were shown to loose activity gradually with complete loss of activity after four repeat runs of 20 hour each. The report does not mention any control runs, which leaves the question of DBT disappearance via adsorption on immobilized beads unanswered and likewise the claim of a better immobilized biocatalyst. 

Improvement of intraparticle mass transfer is the goal of some particle research efforts. One novel approach that has been recently tested is the co-immobilization of algae with bacteria the algae produced oxygen and the bacteria produced the desired product (Chevalier and de la Noue, 1988). Another method used microporous particles entrapped within alginate bead bioparticles to prevent excess biomass growth that could hinder intraparticle mass transfer (Seki et al., 1993). 

Effluent is drawn off from a side port. Under conditions in which a conventional three-phase fluidized bed bioreactor operated in an unstable manner because of gas logging, the new bioreactor converted glucose to ethanol at a 27% higher rate. Saccharomyces cerevisiae was grown in alginate beads for this reaction. 

Mollah, A. H., and Stuckey, D. C., Maximizing the Production of Acetone-Butanol in an Alginate Bead Fluidized Bed Reactor Using Clostridium acetobutylicum, J. Chem. Tech. Biotechnol., 56 83 (1993)... 

In a related approach, alginate beads were modified with aminopropyl-silicate membrane (derived from APTS and tetramethoxysilane). The amino groups remaining on the surface are favorable for the anchoring of biomolecules [84],... 

Lebeau et al. (2002) investigated the sorption of cadmium by viable microbial cells that were free or immobilized in alginate beads by incubating the bacteria in a liquid soil extract medium at pH 5 7 and Cd concentrations of 1 to 10 mg L-1. The percentage of Cd biosorbed reached a maximum (69%) at low Cd concentrations and neutral pH. Thus, the effectiveness of bacteria, inoculated into metal-contaminated soils, would largely depend on the concentration of the metal and its distribution between the biomass and the medium. 

A collective anaerobic and aerobic treatment by immobilized microorganisms was first shown [66, 67] using calcium-alginate-immobilized co-cultures of a facultative anaerobic strain of Enterobacter cloacae. Reaction actually took place in the middle of the alginate beads. In these experiments, the reduced derivatives were oxidized in the outer parts of the alginate beads by a second aerobic strain (two different Alcaligenes species), which had the ability to oxidize 4-chloro-2-aminophenol. 

Adsorption of azo dyes by the biomass is considered as the first step of their biological reduction [39]. Because of adsorption, the dye is concentrated onto the biomass until its saturation the amount of adsorbed dye is then proportional to the amount of biomass [4CM-2]. Steffan et al. [43] observed that 68% Ethyl Orange was rapidly adsorbed on a microbial consortium immobilized in alginate beads, but only after the addition of glucose or starch the dye was effectively degraded. 

Steffan S, Bardi L, Marzona M (2005) Azo dyes biodegradation by microbial cultures immobilized in alginate beads. Environ Int Special Issue Recent Adv Bioremediat 31 (2) 201-205... 

Transfer the alginate beads into a solution of 4% (v/v) glutaraldehyde in 0.1 M2-(N-morpholino) ethanesulphonic acid-NaOH (pH 5.8) that contained 0.4 M glucose. 

After being immersed for 2 h at 4°C, the alginate beads are washed three times with the buffer and kept in the buffer at 4°C for 18 h. 

Cut the alginate beads into small cubes of 1.0 X 1.0 cm2 square using a razor blade. 

Immerse the alginate beads according to a modified method of Akert and Sandri (44) for 3,16, or 20 h at 4°C in the ZIO mixture, which consisted of 3.75% zinc (powder) and 1.25% resublimed iodine crystals in 50 mM 2-(N-morpholino) ethanesulphonic acid-NaOH buffer (pH 5.8) containing 0.2 M glucose and 1% Os04 (MG buffer). 

A strain of Pseudomonas aeruginosa has been recently described, which shows the opposite enantioselectivity, converting racemic arylaminonitriles efficientiy into the D-amino acids. Again, whole-cell biocatalysis worked well, the cells being entrapped in alginate beads. It is unclear whether this biotransformation involves an amide intermediate. 

---