Microbial requirements

So called since they are found in milk, where the iron-binding protein lactoferrin, sequesters iron so tightly that it is no longer available for microbial requirements. 

There are several basic microbial requirements that must be in place if bioremediation is to be successful. 

In relation to the microbial requirements for humidity, the influence of the climate becomes especially obvious for objects that at some stage have been inaccessible, creating a stable climate. Recently, newspapers reported on microbial problems in a cave in France that had been recently opened to the public. Even if only a limited number of visitors are allowed, it is necessary to consider the amount of humidity that is introduced by people. Therefore, in most cases, wall paintings opened to the public are subject to enhanced humidity, due to both human influences and the effects of the external climate after opening. Only very rarely can investigations of the climate and air contamination be carried out before documentation, investigation and consolidation are started. One of the exceptions to be described is the tomb of Queen Nefetari, in the Queens Valley, Thebes. Caves like Altamira or Lascoux have now been completely closed to tourists and are now only accessible to selected visitors with specific interests. 

Some manufacturers of non-sterile excipients use heat, gamma radiation and other methods to reduce microbial burden. These methods are acceptable provided the manufacturer has validated that the product meets microbial requirements and that the process is under control within the manufacturer s specifications. 

It will also be important to understand the rhizosphere ecology around the roots of metal accumulating plants fully. Maximizing the bioavailabihty of the contaminant metals in this zone may require the optimization of the microbial communities, or perhaps the addition of soil amendments. There are early indications that such intervention may be beneficial (88), but research in this area is at a very early stage. 

After World War II, analytical methods for amino acids were improved and new methods were iatroduced. The first was microbial assay usiag lactic acid bacteria which require all of the regular amino acids for growth. Manometric determiaation (by use of a Warburg manometer) of CO2 Hberated by the... 

Enzymatic Determination and Microbial Assay. In these methods, only the desired amino acid is detected ia spite of the presence of other amino acids. No expensive tools are needed for these determiaations. The required nutrients for microorganisms and practical operations for the microbial assay of amino acids have been reviewed (134,135). 

For those pesticides which are utilized as microbial growth substrates, sigmoidal rates of biodegradation are frequentiy observed (see Fig. 2). Sigmoidal data are more difficult to summarize than exponential (first-order) data because of their inherent nonlinearity. Sigmoidal rates of pesticide metabohsm can be described using microbial growth kinetics (Monod) however, four kinetics constants are required. Consequentiy, it is more difficult to predict the persistence of these pesticides in the environment. 

Hospital steriliza tion is more limited in the availabiHty of steriliza tion methods and of packaging materials. Microbial invasion can occur particularly when articles are wrapped in traditional fabrics such as muslin (140-thread-count cotton). The expected shelf life of hospital-wrapped and sterilized articles is considered to be ca 21—30 days when a double-wrapping technique is used. Double-wrapping requires two successive wraps, each having a layer or layers of an approved packaging material. 

Sanitization is a cleaning procedure that reduces microbial contaminants on certain surfaces to safe or relatively safe levels, as defined by the EPA or pubHc health authorities. The article is usually cleaned with hot water and various germicidal detergents. Sanitization can be safe for a product in contact with intact skin or for food utensils, but it is not considered safe for articles to be inserted in the human body. Effective sanitization is a requirement in the processing of reusable medical suppHes before packaging and sterilization. It is also a requirement in the maintenance of utensils and containers used for food preparation. 

The microbial assay is based on the growth of l ctobacillus casei in the natural (72) or modified form. The lactic acid formed is titrated or, preferably, the turbidity measured photometrically. In a more sensitive assay, l euconostoc mesenteroides is employed as the assay organism (73). It is 50 times more sensitive than T. casei for assaying riboflavin and its analogues (0.1 ng/mL vs 20 ng/mL for T. casei). A very useful method for measuring total riboflavin in body fluids and tissues is based on the riboflavin requirement of the proto2oan cHate Tetrahjmenapyriformis which is sensitive and specific for riboflavin. 

As noted above, all vitamin is produced by microbial fermentation. A partial Hst of microorganisms that synthesize vitamin B 2 under appropriate conditions follows. Most strains, in their wild state, produce less than 10 mg/L vitamin although a few approach 40 mg/L. The organisms are both aerobes and anaerobes. The carbon requirements in the fermentations are satisfied from sources as wide ranging as hydrocarbons, methanol, and glucose. 

Besides being slower, anaerobic treatment is more difficult to manage and can generate by-products that are more mobile or toxic than the original compound, for example, the daughter products of TCE, ie, dichloroethenes and vinyl chloride. It requires a longer acclimation period which means slower startup times in the field. The microbial processes are less well understood, and hence, ate less controlled than for aerobic systems. 

Neutralization. Wastewater discharge usually requires a pH between 6 and 9. Exceptions are a biological process in which microbial respiration degrades acidity (acetic acid is oxidized to CO2 and H2O), or one in which the CO2 generated by microbial respiration neutralizes caustic alkalinity (OH ) to bicarbonate HCO. ... 

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