Incubators, chemical sterilization

Benoit and Barriuso (1997) carried out experiments to study the transformation of C-ring-labeled 2,4-D, 4-chlorophenol (4-CP) and 2,4-dichlorophenol (4-DCP) during straw composting under controlled laboratory conditions. Incubation under sterile and nonsterile conditions was done to evaluate the relative importance of the biotic and abiotic processes. Precomposted straw was treated with three chemicals and the availability of the different chemicals was monitored during incubations as well as their degradation. Under nonsterile conditions, Benoit and Barriuso (1997) observed that the mineralization of both chlorophenols reached 20% of the applied... 

Biological indicators (Bis) for use in thermal, chemical or radiation sterilization processes consist of standardized bacterial spore preparations which are usually in the form either of suspensions in water or culture medium or of spores dried on paper, aluminium or plastic carriers. As with chentical indicators, they are usually placed in dummy packs located at strategic sites in the sterilizer. Alternatively, for gaseous sterihzation these may also be placed within a tubular hehx (Line-Pickerill) device. After the sterilization process, the aqueous suspensions or spores on carriers are aseptically transferred to an appropriate nutrient medium which is then incubated and periodically examined for signs of growth. Spores of Bacillus stearothermophilus in sealed ampoules of cultrrre medium are used for steam sterilization morritoring, and these may be incubated directly at 55°C this eliminates the need for an aseptic transfer. 

With the exception of tomato and perhaps citrus fruits, there is no instance in which the presence of a PG in higher plants or macerates has been conclusively demonstrated. Often the types of changes reported suggest 1 that infection by microorganisms rather than naturally occurring enzymes was the cause of the observed chemical transformations. This is especially true with fruit juices, where the rapidly increasing bacterial and mold flora may eventually cause reactions which do not occur when a sterile macerate is incubated. 

Table 16.4 Percent of remaining parathion and of incubation, in 14 sterile soils with different chemical...

Great care should be taken to ensure that all apparatus and chemicals are sterile and free from RNase contamination. Glassware should be incubated at above 150°C for at least 6 h. All solutions not containing amines should be treated with diethyl-pyrocarbonate (DEPC) and autoclaved. If solutions contain amines (Tris), RNase-free chemicals should be added to DEPC-treated distilled water. Gloves should be worn at all times and changed frequently. 

An entirely new incubation technique was developed for water-free hatching of fish eggs . The new method involved low water and energy consumption survival at least in ratios attained by traditional incubators sterilization without malachite green, antibiotics or other banned chemicals minimal labor and hatching at an optimal time. The incubator works for both fresh-water and sea-water fish eggs - preferably for most cultured species. 

The only study located regarding the degradation of 1,1,2-trichloroethane in soil involved subsurface samples taken from the margin of a floodplain near Lula, Oklahoma (Wilson et al. 1983). These samples were obtained both above the water table of a shallow aquifer and in the unconsolidated material in the saturated zone. A portion of the soil was sterilized and slurries were made and test chemical added. Manipulations made with samples from the saturated zone were carried out under nitrogen. After 16 weeks of incubation, no degradation of 1,1,2-trichloroethan was observed in the samples from above or below the water table. These results are in conflict with other studies (Wilson et al. 1983). It has been suggested that the time frame for the experiment may have been insufficient for resident microorganisms to have become acclimated to the chemical (Newsom 1985). 

Ten milliliters of Fries minimal medium supplemented with 1.0% sucrose and 1.5% agar is poured into 20- by 150-mm test tubes which are then divided into experimental and control groups. Varying concentrations of the chemical are added to the experimental group either before autoclaving (with stable compounds) or after autoclaving (with filter-sterilized unstable compounds). The tubes are slanted before the agar cools. Conidia from a 7-day culture of heterokaryon 12 are first suspended in distilled water and then inoculated (- 5 X 10 conidia in 0.5 ml) onto the bottom of each slant. Control and experimental tubes are then incubated at 25°C for 5-7 days. 

In a generalized Adler method, one end of a capillary tube (1 Xl disposable micropipette, 3 cm long with an internal diameter of 0.2 mm) is flame sealed. The entire capillary tube is then quickly passed through a flame, and while warm, the open end is plunged into a reservoir containing the test chemical dissolved in chemotaxis medium. The liquid is drawn up into the capillary as it cools and the filled capillary is then withdrawn from the reservoir and inserted into a chemotaxis chamber, which is constructed by placing a U-shaped melting point capillary tube between a microscope slide and a coverslip (Fig. 1.2). The chamber is filled with an appropriate chemotaxis medium and inoculated with bacteria so that the final concentration is approximately 6 x 10 cells/ml. After a 1-h incubation, the capillary is removed from the chamber and the exterior rinsed with sterile water. The sealed end of the capillary is then broken and the contents are... 

---