Bacterial stability

As already stated, the ameliorative effect of malo-lactic fermentation is equally important in the preparation of red wines—probably more so since a degree of tartrate not desirable in a red wine is often wanted in a white wine. It is also necessary to achieve bacterial stability. So long as malic acid remains in the wine and there is any presence of lactic bacteria, there is a risk, however remote, of delayed fermentation in the bottle accompanied by hazes and gassiness. In former times, French Burgundies often were subject to this accident. Finally, the slight increase of volatile acidity that accompanies malo-lactic fermentation may help to heighten and improve aroma and flavor. 

Pseudomonas that cause skin infections, within 30 s by 2 ppm FAC at pH 7.4 (62). In a series of tests under stabilized conditions (50—100 ppm cyanuric acid), an initial concentration of 3 ppm FAC could not provide water that met the NSPI standards for bacteria or the maintenance of at least a 2 ppm FAC residual. Increasing the initial FAC to 4 ppm resulted in the bacterial criteria being met 100% of the time even when the FAC residual fell below 1 ppm. For heavy bather loads an initial FAC > 4 ppm is recommended. 

Many enzymes need a certain ionic strength to maintain an optimum stabiHty and solubiHty, eg, bacterial a-amylases show optimal stabiHty in the presence of 1—2% NaCl. Some enzymes may need certain cations in low amounts for stabilization, eg, Ca " is known to stabilize subtiHsins and many bacterial a-amylases. Antioxidants (qv) such as sodium sulfite can stabilize cysteine-containing enzymes which, like papain, are often easily oxidized. 

A bacterial isolate APN has been shown to convert a-aminopropionitril enantioselectively to L-alanine (94% yield, 75% e e). However, the major disadvantage of this approach, is the low stability of most aminonitriles in water (for example a-aminophenylacetonitrile in water of pH 7, degrades completely within 48 hours). The aminonitriles are always in equilibrium with the aldehyde or ketone and ammonia/HCN. Polymerisation of hydrogen cyanide gives an equilibrium shift resulting in the loss of the aminonitrile. Therefore, a low yield in amino adds is to be expected, which makes this method less attractive for the industrial synthesis of optically active amino adds. 

Tu, S.-C. (1986). Bacterial luciferase 4a-hydroperoxyflavin intermediates stabilization, isolation, and properties. Method. Enzymol. 133 128-139. 

Tissue and Bacteria Electrodes The limited stability of isolated enzymes, and the fact that some enzymes are expensive or even unavailable in the pure state, has prompted the use of cellular materials (plant tissues, bacterial cells, etc.) as a source for enzymatic activity (35). For example, banana tissue (which is rich with polyphenol oxidase) can be incorporated by mixing within the carbon paste... 

Marlborough, D.I., Miller, D.S. Cammack, K.A. (1975). Comparative study on conformational stability and sub-unit interactions of two bacterial asparaginases. Biochimica Biophysica Acta, 386, 576-89. 

Photosynthetic reaction centers from Rhodobacter sphaeroides and bacteri-orhodopsin (BR) from purple membrane (PM) have been used for their unique optoelectronic properties and for their capability of providing light-induced proton and electron pumping. Once assembled they display extremely high thermal and temporal stability... 

Delays of more than two hours after the collection is completed may lead to markedly erroneous results. Urines with bacterial overgrowth, hemolyzed blood, or those obtained following any type of instrumental examination of the urinary tract may also lead to erroneous results, and should not be used for assays of enzyme activities. The stability of some clinically important enzymes in the various body fluids is given in Table IV. 

The transport of EDTA into a bacterial strain capable of its degradation has been examined (Witschel et al. 1997). Inhibition was observed with DCCD (ATPase inhibitor), nigericin (dissipates ApH), but not valinomycin (dissipates Av /), and was dependent on the stability constant of metal-EDTA complexes. 

Schldmann M, P Fischer, E Schmidt, H-J Knackmuss (1990b) Enzymatic formation, stability, and spontaneous reactions of 4-fluoromuconolactone, a metabolite of the bacterial degradation of 4-fluorobenzoate. J Bacterial 172 5119-5129. 

A hydraulic fracturing fluid containing guar gum or other natural polymers can be stabilized against bacterial attack by adding heterocyclic sulfur... 

Another issue in the preparation of reference material is the required shelf life. The shelf life of reference material is the time that it remains stable under proper storage conditions. Depending on the nature of the mechanisms affecting the stability of the material, various actions can be taken to improve the shelf life. Reduction of the moisture content is one of the first options to be considered. In many cases, moisture plays a key role in mechanisms leading to instability of the matrix and/or parameters. In other cases, sterilization or pasteurization of the material might be considered in order to stop bacterial activity. When preparing solutions, additives may increase the shelf life. Obviously, the shelf life of material is also a function of the storage conditions. 

Stability of several enzymes like proteases from thermophilic micro-organisms can be increased in aqueous-organic biphasic systems. Owusu and Cowan [67] observed a strong positive correlation between bacterial growth temperature, the thermostability of free protein extracts, and enzyme stability in aqueous-organic biphasic systems (Table 1). Enzymes, like other cell components (membranes, DNA, (RNA ribosomes), are adapted to withstand the environmental conditions under which the organism demonstrates optimal growth. 

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