Microbial cells, immobilization

These reactors contain suspended solid particles. A discontinuous gas phase is sparged into the reactor. Coal liquefaction is an example where the solid is consumed by the reaction. The three phases are hydrogen, a hydrocarbon-solvent/ product mixture, and solid coal. Microbial cells immobilized on a particulate substrate are an example of a three-phase system where the slurried phase is catalytic. The liquid phase is water that contains the organic substrate. The gas phase supplies oxygen and removes carbon dioxide. The solid phase consists of microbial cells grown on the surface of a nonconsumable solid such as activated carbon. 

In all our work, we have used reconstituted bovine hide collagen as the carrier matrix of choice. The biomaterial, collagen, offers a number of unique advcintages as a support for microbial cell immobilization. Other publications from our laboratory describe these advantages as well as the procedures to prepare fixed cells in detail ( 3, ). We have attached many different microorganisms in this manner some of the ccxnplex reactions mediated by such fixed cell preparations are shown in Table 4. 

As has been shown already on an Industrial scale, fermentation can be substituted by heterogeneous catalysts with resting microbial cells Immobilized In polymeric carriers. Repeated use of the once formed biomass, continuous process operation, and elimination of costly separation steps of product solution from biomass are obvious advantages of this new technology. Some principal aspects of a) Immobilization methodology, b) catalyst effectiveness, and c) operational stability shall be outlined In this contribution. 

Sodium chlorite oxidation of com and rice starches is recommended for the production of textile sizes (101) and oxidized starch is recommended as a hardening agent in the immobilization of microbial cells within gelatin (102). 

Because enzymes can be intraceUularly associated with cell membranes, whole microbial cells, viable or nonviable, can be used to exploit the activity of one or more types of enzyme and cofactor regeneration, eg, alcohol production from sugar with yeast cells. Viable cells may be further stabilized by entrapment in aqueous gel beads or attached to the surface of spherical particles. Otherwise cells are usually homogenized and cross-linked with glutaraldehyde [111-30-8] to form an insoluble yet penetrable matrix. This is the method upon which the principal industrial appHcations of immobilized enzymes is based. 

Chibata, I., Immobilized Microbial Cells with Polyacrylamide Gel, Carrageenan and their Indushial Application, In Immobilized Microbial Cells , chap. 3. American Chemical Society, Washington, D.C., 1979. 

All soil metabolic proce.sses are driven by enzymes. The main sources of enzymes in soil are roots, animals, and microorganisms the last are considered to be the most important (49). Once enzymes are produced and excreted from microbial cells or from root cells, they face harsh conditions most may be rapidly decomposed by organisms (50), part may be adsorbed onto soil organomineral colloids and possibly protected against microbial degradation (51), and a minor portion may stand active in soil solution (52). The fraction of extracellular enzyme activity of soil, which is not denaturated and/or inactivated through interactions with soil fabric (51), is called naturally stabilized or immobilized. Moreover, it has been hypothesized that immobilized enzymes have a peculiar behavior, for they might not require cofactors for their catalysis. 

Samejima, H., Nagashima, M., Azuma, M., Noguchi, S., and Inuzuka, K., Semicommercial Production of Ethanol using Immobilized Microbial Cells, Annals New York Academy of Sciences, 434 394 (1984)... 

The sol-gel-entrapped microbial cells have shown excellent tolerance to different alcohols [99], The immobilized E. coli cells followed the Michaelis-Menten equation when quantified with the (3-glucosidase activity via the hydrolysis of 4-nitrophenyl-(3-D-galactopyranosdie [142], The sol-gel matrices doped with gelatin prevented the cell lysis, which usually occurs during the initial gelation process [143], Microorganisms are now widely used in the biosorption of different pollutants and toxicants. Bacillus sphaericus JG-A12 isolated from uranium mining water has been entrapped in aqueous silica nanosol for the accumulation of copper and uranium [144], Premkumar et al. [145] immobilized recombinant luminous bacteria into TEOS sol-gel to study the effect of sol-gel conditions on the cell response (luminescence). The entrapped and free cells showed almost the same intensity of luminescence (little lower), but the entrapped cells were more stable than the free cells (4 weeks at 4°C). This kind of stable cell could be employed in biosensors in the near future. 

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. 

The immobilization of microbial cells under conditions where an activity or set of enzymic activities remains intact, but the normal metabolic processes cease, represents a novel technique for enzyme immobilization. Moreover, immobilized cells might enable the standard fermentation methods to be replaced by immobilized -cell -based continuous processes. 

Karube I, Mitsuda S, Matsunaga T, Suzuki S (1977) A rapid method for estimation of BOD by using immobilized microbial cells. J Eerm Technol 55 243-248... 

Bubble columns in which gas is bubbled through suspensions of solid particles in liquids are known as slurry bubble columns . These are widely used as reactors for a variety of chemical reactions, and also as bioreactors with suspensions of microbial cells or particles of immobilized enzymes. 

Subsurface environmental conditions are suboptimal with low temperatures and low concentrations of growth nutrients. The decline of bacterial inoculae by protozoan predation is of major concern in soil (Acea etal., 1988 Acea Alexander, 1988 Casida, 1989) but may not be a factor in saturated subsurface environments. Immobilization of cells to carrier material may enhance microbial survival in the environment through control of predation and supply of nutrients and moisture. Stormo Crawford (1992) developed a cell immobilization technique for production of small beads (2-50 /rm) consisting of agarose and cells of PCP-degrading Flavobacterium sp. Microencapsulated Flavobacteria efficiently degraded PCP and survived for two years in soil columns at environmental conditions (Stormo Crawford, 1994). These results show that microencapsulation may be a very useful tool in in situ bioremediation. 

Chibata I, Wingard LB (eds) (1983) Immobilized microbial cells applied biochemistry and bioengineering, vol 4. Academic, New York... 

S Fukui, A Tanaka. Immobilized microbial cells. Annu Rev Microbiol 36 145-172, 1982. 

A Freeman, Y Aharonowitz. Immobilization of microbial cells in crosslinked, polymerized linear polyacrylamide gels antibiotic production by immobilized Streptomyces clavuligerus cells. Biotechnol Bioeng 23 2747-2759, 1981. 

Yenugopal Y, Alur MD, Nerkar DP. Solubilization of fish proteins using immobilized microbial cells. Biotechnol Bioeng 1989 33 1098-1103. 

Microbial cells displaying foreign proteins can be considered as microscopic protein matrices and be used in those applications that require protein immobilization. The display of enzymes such as /1-lactamase [71] and cellulase [16] on the surface of E. coli has demonstrated the possibility of creating immobilized cell biocatalysts. 

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