Entrapment alginate

The mixed solution obtained was then placed in a syringe and allowed to drop into a sterile 0.2M CaCli solution that was stirred continuously. Alginate drops solidified upon contact with CaCh, forming beads and thus entrapping bacteria cells. The beads were allowed to harden for 30 minutes at 37 C and then washed with sterile saline solution to remove excess calcium ions and untrapped cells. 

Effect of bead diameter on lactic acid yield is clearly revealed in Fig.6. The optimum bead diameter for the fermentation of lactic acid for cell entrapped in Ca-alginate is 1.0mm with a yield of 30.27 gL and 96.7%. Increasing bead diameter beyond this value did not improve lactic acid production. Smaller bead diameter yields more lactic acid production, due to an increase in the surface volume ratio [9]. A further increase in bead diameter to 5.0mm results in a decrease of lactic acid production to 17.65 gL or 50.7%. 

At end, it is important to mention that calcium pectate gel beads were compared with calcium alginates gel beads for all entrapment uses [65, 66] in this work, the authors determined the pore size of the beads by size exclusion chromatography using dextran standards and other solutes. 

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). 

Chen, J.P. and Wang, H.Y. (1998) Improved properties of bilirubin oxidase by entrapment in an alginate-silicate sol-gel matrix. Biotechnology Techniques, 12, 851-853. 

Kawakami, K. and Furukawa, S.Y. (1997) Alcohol-oxidation activity of whole cells of Pichia pastoris entrapped in hybrid gels composed of Ca-alginate and organic silicate. Applied Microbiology and Biotechnology, 67, 23-31. 

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. 

Cell cultures of Catharanthus roseus entrapped in calcium alginate have been employed by Takemoto and Achiwa to deracemize pyridyl alcohols such as 15 and 16 [17] (Scheme 8). 

Roy, I. and Gupta, M.N., Hydrolysis of starch by a mixture of glucoamylase and pullulanase entrapped individually in calcium alginate beads, Enzyme Microbial Tech., 34 (2004) 26-32. 

Villegas, M., Leon, R. and Brodelius P. E. 1999. Effects of alginate and immobilization by entrapment in alginate on benzophenanthridine alkaloid production in cell suspension cultures of Eschscholtzia californica. Biotechnology Letters, 21(1) 49-55. 

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