Microorganisms sterilization

Absence of microorganisms Sterility test (see also Chapter 23)... 

During sample preparation and electrophoresis DNA will not be denaturated, i.e., the double strand and higher elements of structure stay unaffected. To avoid unwanted further fragmentation all manipulations have to be done without possible contaminations by fingerprints, droplets of saliva or microorganisms. Sterilized materials are recommended. 

Since the inactivation of bacteria follows an exponential decay process with a limiting value tending towards zero, the absolute sterility can never be obtained. The D,g value is the absorbed dose required to reduce a microbial population to 10% of its initial value, so that in industrial applications, a SAL value of 10" is reached after 3 x D value. For drugs, a dose of 25 kGy (or kJ kg ) is generally higher than 6 x D,g value and achieves the minimum SAL required of 10 . Many reviews demonstrated that for drugs with low bioburdens (initial contamination by microorganisms), sterilization was achieved with doses even lower than 15 kGy. 

Sterilization in place—Closed systems such as process vessels, dryers, centrifuges, isolators, and other items should be subjected to a validated sterilization procedure, which assures that all internal surfaces have been rendered free of microorganisms. Sterilization-in-place (SIP) procedures reduce the number of aseptic manipulations necessary to ready the equipment for use in the aseptic production processes and as such are considered preferable to aseptic assembly of systems from individually sterilized components (25). The SIP procedure should allow the system to maintain sterility until ready for use without aseptic manipulations. Sterilization-in-place procedures could employ steam, gas, dry heat, radiation, chemical agents, or other validateable sterilization procedure. 

Microorganisms are ubiquitous, thus microbial contamination is the rule the total absence of microbes, ie, sterility, is the exception. Many microorganisms might be considered mainstream, growing under typical ambient conditions, but there are almost always strains that are capable of surviving and multiplying under the extremes of pH, salinity, pressure, and temperature. 

Product Heat Treatment. Equivalent heat treatment for destmction of microorganisms or inactivation of enzymes can be represented by plotting the logarithm of time versus temperature. These relationships were originally developed for sterilization of food at 121.1°C, therefore the time to destroy the microorganism is the V value at 121.1°C (250°F). The slope of the curve is and the temperature span is one log cycle. The heat treatment at 131°C for one minute is equivalent to 121.1°C for 10 minutes (Fig. 10). 

Pasteurization does not mean sterilization of the beer, ie, killing all microorganisms, but rather a reduction and inactivation of the microorganisms. The result of the heat treatment depends not only on time and temperature, but also on the number of microorganisms present. It is important that tanks. 

Sporicide kills (inactivates) bacterial spores, and is therefore expected to kill all other microorganisms of less resistance. According to the AO AC International it may not kill 100% of the spores, and therefore may not be as powerful as a sterilant. However, according to the EPA, sporicide and sterilant are considered identical. 

Chlorine Dioxide. Like ozone, chlorine dioxide [10049-04-4] is a powerflil oxidant. It is usually generated as used. It has been used for disinfecting drinking water and bleaching paper pulp. Its effectiveness in killing microorganisms is well documented (305,306), and it has received recent study as a gas to sterilize medical devices. It requites 50% rh or higher to be effective. Bacterial cells had a D-value of 2.6 min and spores of 24 min (307). 

To prevent contamination with undesirable microorganisms, the fermentor and auxiUary equipment must be sterilized before inoculation. This is achieved by steam, ie, at least 20 min at 121°C. The incoming air is filtered. 

Relative thermal resistance for the different types of microorganisms encountered in typical environments associated with fermentation broths is shown in Table 24-3. Bacterial spores are far more resistant to moist heat than are any other type oi microbial contaminants thus, a sterilization cycle based on the destruction of bacterial spores should destroy all life. 

In the holding section of a continuous sterilizer, correct exposure time and temperature must be maintained. Because of the distribution of residence times, the actual reduction of microbial contaminants in the holding section is significantly lower than that predicted from plug flow assumption. The difference between actual and predicted reduction in viable microorganisms can be several orders of magnitude therefore, a design based on ideal flow conditions may fail. 

Batch processing A processing technique in which a bioreactor is supplied with substrate and essential nutrients, sterilized and inoculated with microorganisms, and the process is run to completion followed by removal of products. 

This material was made up with distilled water to provide 41 g per liter, and the mixture was adjusted to pH 7.0 with potassium hydroxide solution. To the mixture were added per liter 5.0 g of calcium carbonate and 7.5 ml of soybean oil. 2,000 ml portions of this medium were then added to fermentation vessels, equipped with stirrers and aeration spargers, and sterilized at 121°C for 60 minutes. After cooling the flasks were inoculated with a suspension of strain No. ATCC 11924 of Streptomyces lavendulae, obtained from the surface of agar slants. The flasks were stirred for 4 days at 28°C at approximately 1,700 rpm. At the end of this period the broth was found to contain cycloserine in the amount of about 250 C.D.U./ml of broth. The mycelium was separated from the broth by filtration. The broth had a pH of about 7.5. Tests showed it to be highly active against a variety of microorganisms. 

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