Micro-organisms biocides

The risk that biocides insure against is that caused by infections of micro-organisms, the so-called "invisible enemy", and to appreciate the risks involved it s first necessary to learn something about this group of living creatures. 

Wooden hatch covers may support and encourage growth, particularly of fungi, and powders, caked onto the stirrer shaft and lid, moistened with condensation and not biocidally protected, can also become colonised by micro-organisms. 

The wide range of micro-organisms found in emulsion paints dictates the use of broad spectrum products. However, many biocides are less active against fungi than bacteria (or vice versa) and it is therefore important to ensure that biocide manufacturers claims are backed up by results of realistic in-use tests. 

Micro-organisms inhabit the aqueous phase of an emulsion and thus it is necessary for the biocide not only to be water soluble but also to remain in the aqueous phase. 

Antibiotics usually have a specific site or mode of action whereby they achieve a selective toxic effect against bacteria but not human host cells. In contrast, biocides frequently have multiple target sites in the bacterial cell and by their very nature are often toxic not only to bacteria and other micro-organisms but also to host cells [7,23,24], Thus, mutation at, or absence of, a normal target site (or the presence of an additional target site) may be responsible for producing resistance to antibiotics but not to biocides. 

It is also important to notice that SCFs have biocide properties against most micro-organisms (fungi, bacteria, viruses) (20-25) and, even if it cannot be considered as a real sterilizing agent, SCF processes are intrinsically sterile and never increase the bioburden. 

Biocide Kills or disables micro-organisms so that they do not stick to surfaces. 

Biocide Biocide concentration mg/l product Micro-organism population, cfu/ml after h 2h Ih ... 

The starch tank was not emptied during the run cycle and so provided a continuous reserve of micro-organisms. On adding an appropriate biocide to the starch tank a constant, high FPR was achieved. 

Chemicals used against micro-organisms may be divided into two groups, bacteriostatic and bactericidal (biocidal). Bacteriostatic compounds are those which stop bacteria growing, whilst bactericidal compounds are those which kill bacteria. The division is not clear cut as many compounds are bacteriostatic at low concentrations and bactericidal at high concentrations. The extent of the bactericidal effect of any compound is governed by four factors. These are ... 

The process of sterilisation is required for any product used in a situation where there is a risk of infection. Sterilisation requires the application of a chemical (biocide) to a product, or the physical removal of micro-organisms from the product. The objective is to kill the bacteria, the definition of bacterial death being the irreversible loss of reproductive ability. There are a number of chemical and physical methods available to achieve this objective. The physical methods... 

This short list, still remarkable for its simplicity, led inevitably to the organometallic compounds and polyhalogenated phenol derivatives — active ingredients which are both highly effective and highly persistent and which may indeed be termed biocides , since they are harmful not only to micro-organisms, but also to plants, insects, snails, fish and other organisms — in short, to all forms of life. 

The activity of biocides depends on three main factors (a) the nature of the physical environment, (b) the nature and condition of the micro-organism, and (c) the ability of the organism to render the biocide inactive. These processes have been extensively reviewed [50] and only those specific aspects relevant to the aldehydes will be discussed here. 

Most studies on the mode of action of biocides have examined vegetative bacteria, although recent work has also provided information about the inactivation of spores. Other micro-organisms have perhaps been more neglected, although there are some data on the mechanism of action of aldehydes against fungi and viruses. 

Annex IVA includes the data requirements for active organisms such as fungi, micro-organisms and viruses and Annex IVB for biocidal products containing such active organisms. 

Temperature Low temperature (below 30°C) or warm machines (above 50°C that are often observed with TMP and also with DIP treated with hot dispersion) will reduce biological activity and make the machines less favourable for microbial growth. The use of non-oxidising biocides can then be reduced and the treatment mainly based on the usage of polymers/surfactants blend to inhibit the growth of micro-organisms or remove the biofilm. 

In order to obtain the strong biocidal effect needed to avoid mould formation on the textile materials and to avoid decomposition of the textile materials, it is needed that active component diffuses out of the textile material to the micro-organism (e.g. by water through hydrolytic decomposition or dissolving). Various classes of biocidal agents that can provide this effect, are ... 

Biocides To control the growth of micro-organisms and bacteria... 

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