Surfactants microbial attack

The increasing popularity of biodegradable materials, which are more susceptible to microbial attack, has boosted the demand for preservation. If the product does not already contain ingredients that are themselves preservatives, such as cationic surfactants, acids, or bases, preservatives may need to be added. The required level of preservatives can be related to water availability (AW), which is defined as the ratio between the water vapor pressure over a substance and the water vapor pressure over pure water at the same temperature [17], In general, an A W of below 70% should be targeted to prohibit microorganism growth [18],... 

Hazardous substances may be protected from microbial attack by physical or chemical envelopes. These protective barriers must be destroyed mechanically or chemically to produce fine particles or waste suspensions to increase the surface area for microbial attachment and subsequent biodegradation. Another way to increase the bioavailability of hydrophobic substances is washing of waste or soil by water or a solution of surface-active substances (surfactants). The disadvantage of this technology is the production of secondary hazardous... 

Figure 2 presents a schematic of one scenario in which nonionic surfactant may assist biomineralization. In this situation micellar nonionic surfactant has solubilized HOC from soil. As microorganisms deplete aqueous-phase HOC via mineralization, the micelle releases HOC to solution. HOC exit rates from micelles may be significantly faster than HOC desorption rates from soil, and this condition thereby potentially enhances the availability of HOC to the microorganism. Other researchers (25, 28) suggested that surfactants may make HOCs more available for microbial attack in soil by decreasing the interfacial tension between the compound and water. 

Liquid raw materials such as defoamers, surfactants, starch solutions and hydroxyethyl cellulose solutions may themselves be susceptible to microbial attack and, unless carefully manufactured and protected with biocides, can also introduce contamination into the product. 

Although non-ionic surfactants are often chosen for emulsified systems because of their relatively low toxicity, several problems in formulation have arisen with their use. Most emulsions of edible fats and oils must be preserved against microbial attack. The most effective preservatives have often been the p-hydroxybenzoic acids. Unfortunately, these acids are inactivated by interaction... 

A great deal of work has also been carried out on the biodegradation of nonionic surfactants, in this case the ethoxylates used in detergents and cleaning agents. However, the metabolic mechanism has not been investigated to the same extent as with linear alkylbenzenesulfonate. The microbial attack takes place on the ethylene oxide chain and also on the alkyl group of the molecules. 

As outlined in the previous sections very extensive microbial attack takes place in the course of the biological effluent treatment. Microorganisms which degrade surfactants are present already in the sewer system before the treatment plant as well as in the latter, and also later in the natural waters. An adverse effect of the cur-... 

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