Water activity bacterial growth

Chemical and physical processes may limit the stability of active substance, base and excipients in suppositories. Also the packaging and the conditions and times of storage need attention. Suppositories with a fatty or a macrogol base do not contain water. Therefore bacterial growth is unlikely and preservation is not needed. 

The optimal temperature for bacterial growth is between 20 and 37°C. For every 10°C decrease in temperature, bacterial activity is approximately halved. Temperature in deep groundwater is rather constant. However, for shallow soil and water, in cold weather the rate of biodegradation becomes depressed compared to in warmer weather, and therefore warm water may need to be injected into the subsurface. 

Although there have only been a few studies to date, it has been suggested that coastal plumes (Turner et al., 1996 Simo et al., 1997) and estuaries (Iverson et al., 1989 Cerqueira and Pio, 1999) may be important atmospheric sources of DMS. DMS, a compound produced by certain phytoplankton, has been shown to have possible implications for climate control once released into the atmosphere (Charlson et al., 1987). DMS is formed by cleavage of dimethylsulfoniopropionate (DMSP) (Kiene, 1990). In fact, DMSP, shown to be correlated with bacterial activity, may provide as much as 100% of the sulfur and 3.4% of the carbon required for bacterial growth in oceanic waters (Kiene and Linn, 2000). Other sulfur compounds such as COS and carbon disulfide (CS2) have also been shown to be possible sources of S in estuaries. For example, significant concentrations of COS and CS2 were found in four European estuaries, 220 150 and 25 6 pM (Sciare et al., 2002). COS is the most abundant sulfur compound in the... 

On the contrary, lysis and particularly viral lysis could be a major process in these bioassays. In cultures of natural marine bacteria inoculated into 0.2 pm filtered sea water, Wilcox and Furhman (1994) reported that virus abundance increased after few days of bacterial growth. The high abundance and production of bacteria in the HFe bioassay could enhance viral activity and consequently increase specific mortality rates. In agreement with this, during the mesoscale Fe fertilization EISENEX, a higher viral infection of bacterioplankton was estimated in the Fe-enriched patch (Weinbauer et al. 2003). Lysis could be of significance in Fe-limited ecosystems, as Fe released via lysis can be highly bioavailable (Poorvin et al. 2004). 

Water activity has a profound effect on the rate of many chemical reactions in foods and on the rate of microbial growth (Labuza 1980). This information is summarized in Table 1-9. Enzyme activity is virtually nonexistent in the monolayer water (aw between 0 and 0.2). Not surprisingly, growth of microorganisms at this level of aw is also virtually zero. Molds and yeasts start to grow at aw between 0.7 and 0.8, the upper limit of capillary water. Bacterial growth takes place when aw reaches 0.8, the limit of loosely... 

U. Ambrose, K. Middleton and D. Seal. In vitro studies of water activity and bacterial growth inhibition of sucrose-polyethylene glycol 400-hydrogen peroxide and xylose-polyethylene glycol 400- hydrogen peroxide pastes used to treat infected wounds. Antimicrob. Agents Chemother., 35, 1799-803 (1991)... 

Fruits have an inherent acidity and contain various organic acids that protect against bacterial invasion (Fielding, Cook, and Grandison, 1997). Fruit juices and other fruit products may be easily spoiled as a result of contamination due to high water activity, which allows microbial growth... 

In the USA, water fluoridation became widely available after 1955 and fluoridated toothpastes after 1975 and caries in adolescent children has decreased by 66%. The effects of fluoride on caries are topical from the surface to the interior. Water fluoridation ensures small amounts of fluoride throughout a tooth and fluoridated toothpaste enhances the fluoride concentration at the tooth surface. Protection from caries by artificial fluoridation of water supplies and fluoridated toothpaste is cumulative. Investigations as to how fluoridation protects from caries has identified three mechanisms of caries protection (1) inhibition of demineralization, (2) enhancement of remineralization, and (3) inhibition of bacterial enolase activity reducing lactate production from ingested carbohydrates. Fluoride has little effect on bacterial growth, and gives no direct protection from gingivitis, periodontitis, or osteoporosis... 

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