Immobilization medium bacteria

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. 

Immobilization on solid matrix by adsorption on ion exchange material or binding via lecitin is widely used for chemotrophic bacteria [Jack, Zajic, 1977] but not reported for photosynthetic microorganisms. In these matrixes a direct contact of microorganisms with medium was possible. However, matrixes and ion exchange material for immobilization of photosynthetic microorganisms should be transparent or translucent. 

Cephalosporin is determined from the proton concentration generated in a medium by using immobilized bacteria. A microbial sensor composed of a bacteria-collagen membrane reactor and a combined glass electrode was applied to the determination of cephalosporins in fermentation media. The system used for continuous determination... 

Both methods, however, have disadvantages. Biochemical transformations can have limited application, and there is always the problem of finding the proper bacteria, animal preparation, or enzyme and culture medium to effect a new synthesis. In addition, product isolation—such as in the production of an optically active < -deuteroalcohol, where a small amount of product must be isolated from a large quantity of spent fermentation liquor—can present formidable separation problems. Product isolation from enzyme systems, especially immobilized enzymes, could be much simpler, however. 

Preliminary experiments indicated that the activity of bacitracin production by immobilized whole cells was remarkably reduced at the second reaction when a fermentation medium was used. Furthermore, the growth of leaked bacteria was observed when a fermentation medium (starch-bouillon) was employed for bacitracin production. Therefore, the effect of medium composition on bacitracin productivity was examined. As shown in Table III, bacitracin productivity in a medium... 

Recombinant bacteria and yeast cells are efficiently cultivated in a fed-batch mode [28-30], Old-fashioned processes use the simple batch mode. The fed-batch mode has higher productivity because the physiological requirements of the cells can be better adjusted in fed-batch culture. Animal cells arc often cultivated in continuous mode [28], The cells are immobilized or retained by special devices in the fermenter and the culture medium is continuously fed to the bioreactor. In this case, the product can be harvested continuously. So far, continuous purification processes have not been used on an industrial scale to... 

As mentioned above, immobilized cells are studied mainly for practical reasons, since they show a number of economic advantages over the use of growing cells or cell suspensions. Production of organic acids is one of the prospective applications of immobilized cells. Another one is related to the release of nitrogenous bases and some nucleosides by immobilized cells. In nitrogen-starved immobilized cells the levels of all metabolites (first of all, nucleotides) are reduced (Leps and Ensign, 1979). It was shown (Ikonnikov et al., 1982) that immobilized cells of propionic acid bacteria, incubated periodically in nitrogen-free medium, released substances of protein and nucleic acid nature, whose quantity decreased with the time of incubation in... 

It is remarkable ftiat cells of the strain AKU-1251 secreted the vitamin synthesized, although the authors could not exclude that most of the vitamin released by the immobilized cells resulted from cell autolysis. The bacteria multiplied inside the gel, because the medium contained all the compounds required for growth. 

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