Microbial selective

T. Mino (2000). Microbial selection of polyphosphate-accumulating bacteria in activated sludge wastewater treatment process for enhanced biological phosphate removal, Biochemistry (Moscow), 65, 541-549. 

L. gallinarum, L. plantarum, Propionibacteriumfreudenreichii, and Streptococcus bovis, and these bacterial types interestingly are localized in the rumen or small intestine. As a direct-fed microbial, selected L. acidophilus strains, alone or in combination with P. freundenreichii, have been the most thoroughly studied and often are very effective at reducing the prevalence of fecal shedding of E. coli 0157 H7 when dosed at 10 cells per animal daily (Peterson et al., 2007a Tabe et al., 2008 Younts-Dahl et al., 2005). 

When inferring the mechanisms involved in a process one should realize that mechanisms with characteristic time magnitudes larger or smaller than the process time can be ignored. In a microbial fermentation, for example, metabolic reactions in the cell are too fast (characteristic times less than 10 sec) and microbial selection is too slow (more than 10 sec) to influence the process. 

Some examples of different effects depending on the kind of biological colonization (Bastian et al. 2009 Fonseca et al. 2010 Barrionuevo and Gaylarde 2011 de los Rfos et al. 2012) and there could be microbial selection by the use of biocides -see e.g. Bastian et al. (2009). 

Thus, in determining the mechanism of chromate or uranyl reduction, one must consider the microbial selection of terminal electron acceptor(s) and the resulting concentration of competing chemical reductants such as Fe(II) or S(-II). 

Water Activity. The rates of chemical reactions as well as microbial and en2yme activities related to food deterioration have been linked to the activity of water (qv) in food. Water activity, at any selected temperature, can be measured by determining the equiUbrium relative humidity surrounding the food. This water activity is different from the moisture content of the food as measured by standard moisture tests (4). 

Aliphatic-Garboxylics. There are only two herbicides present in this class, trichloroacetate [76-03-9] (TCA) and dalapon [75-99-0]. These are used primarily for the selective control of annual and perennial grass weeds in cropland and noncropland (2,299). Dalapon is also used as a selective aquatic herbicide (427). Dalapon and TCA are acidic in nature and are not strongly sorbed by sods. They are reported to be rapidly degraded in both sod and water by microbial processes (2,427). However, the breakdown of TCA occurs very slowly when incubated at 14—15°C in acidic sods (428). Timing not only accelerates this degradation but also increases the numbers of TCA-degrading bacteria. An HA has been issued for dalapon, but not TCA (269). 

Reverse osmosis membrane separations are governed by the properties of the membrane used in the process. These properties depend on the chemical nature of the membrane material, which is almost always a polymer, as well as its physical stmcture. Properties for the ideal RO membrane include low cost, resistance to chemical and microbial attack, mechanical and stmctural stabiHty over long operating periods and wide temperature ranges, and the desired separation characteristics for each particular system. However, few membranes satisfy all these criteria and so compromises must be made to select the best RO membrane available for each appHcation. Excellent discussions of RO membrane materials, preparation methods, and stmctures are available (8,13,16-21). 

A microbial source for a food enzyme must be nonpathogenic and nontoxicogenic. Manufacturers of microbial food enzymes have always selected their production microorganisms from the safe end of the spectmm of available sources. Consequendy, a few species have acquired a record of safe use as sources of a wide variety of food enzymes. 

In section 9.3, we discussed in general terms the use of microbial metabolism to selectively remove the side chain from sterols to produce steroids. This removal may also be accompanied by some modification to the ring structure. We did not, however, discuss in any detail any specific reactions. In this section we will focus on some specific reactions. 

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