Microbial degradation surfactants

Cain RB (1981) Microbial degradation of surfactants and builder components. In Microbial Degradation of Xenobiotics and Recalcitrant Compounds (Eds T Leisinger, AM Cook, R Hiitter, and J Niiesch), pp. 325-370. Academic Press, London. 

White GF, NJ Russell (1994) Biodegradation of anionic surfactants and related molecules. In Biochemistry of Microbial Degradation (Ed C Ratledge), pp. 143-177. Kluwer Academic Publishers, Dordrecht, The Netherlands. 

These bioavailability problems may be overcome by the use of food-grade surfactants,17 which increase the availability of contaminants for microbial degradation. 

Investigation of the pronounced resistance of ABS to microbial degradation demonstrated that the branched alkyl chain derived from tetrapropylene was responsible for the longevity of ABS in the aquatic environment [74], Shortly after this discovery, the surfactant industry reacted and made attempts—in some countries additionally forced by legal restrictions—to provide an alternative surfactant with comparable functional properties, but with inherent biodegradability. The outcome was the introduction of LAS on the detergent market. After the switch from ABS to LAS in almost all nations in the mid 1960s, a substantial drop in the levels of ABS was observed [8],... 

The importance of a good chromatographic separation prior to the mass spectrometric analysis has to be underlined in face of the large number of possible surfactant-derived isobaric compounds to be encountered during the microbial degradation of LAS containing traces of DATS. For example, Cn-LAS and methylated C8-DATSC yield the same molecular ion [M — H] at m/z 311 identical masses of the [M — H] ions (m/z 355) are calculated for methylated Cn-SPC and dimethylated C8-DATSdC. 

The relatively strong interaction of cationic contaminants with negatively charged soil constituents, for example, is expected to decrease bioavailability. This has been shown to be the case for diquat, in which intercalation into internal clay surfaces eliminates microbial degradation of the compound (Weber and Coble, 1968). Decreased bioavailabilities forbenzylamine in association with montmorillonite (Miller Alexander, 1991), quinoline bound to hectorite or montmorillonite (Smith etal., 1992), and cationic surfactants with humic materials or montmorillonite (Knaebel et al., 1994) have also been reported. 

Hales, S.G. 1981. Microbial degradation of linear ethoxylate surfactants, Ph.D. Thesis, Univ. Wales, Cardiff. 

A series of related experiments investigated nonionic surfactant sorption onto soil, mechanisms of nonionic surfactant solubilization of polycyclic aromatic hydrocarbon (PAH) compounds from soil, and microbial mineralization of phenanthrene in soil-aqueous systems with nonionic surfactants. Surfactant solubilization of PAH from soil at equilibrium can be characterized with a physicochemical model by using parameters obtained from independent tests in aqueous and soil-aqueous systems. The microbial degradation of phenanthrene in soil-aqueous systems is inhibited by addition of alkyl ethoxylate, alkylphenyl ethoxylate, or sorbitan- (Tween-) type nonionic surfactants at doses that result in micellar solubilization of phenanthrene from soil. Available data suggest that the inhibitory effect on phenanthrene biodegradation is reversible and not a specific, toxic effect. 

The application of surfactants or emulsifying agents may decrease interfacial tension and assist solubilization of sorbed HOCs from soils, thereby making the hydrophobic compounds more available for microbial degradation (22, 23). However, the experimental observations of the effects of surfactant addition on microbial degradation of HOCs are not always consistent, nor has a general explanation been advanced for their influence. Some of the varied observations of surfactant effects on biodegradation are summarized in Table I (24-37). 

The likely causes for the inhibition of microbial degradation of phenanthrene at higher surfactant doses are... 

Available data suggest that the supra-CMC inhibitory effect on biodegradation is reversible and not a specific toxic effect. Partial inhibition of microbial degradation of phenanthrene was observed for nonionic surfactants at sub-CMC doses. It is not clear whether these effects result from surfactant interactions with microorganisms or from preferential use of surfactant as substrate or source of carbon. The effects of surfactant monomers and micelles on microbial cell surfaces and constituents, and effects related to preferential substrate utilization and mineralization of degradation products, must be better understood in order to evaluate whether synthetic surfactants may be employed advantageously to enhance bioremediation in soil-water systems. 

Some of the usual product testing becomes even more important with these dilute spray cleaners. For instance, higher concentrations of solvents could change the flammability of the product, and therefore the shipping of the product. The abundance of water and the low concentration of surfactant might make the product more susceptible to microbial degradation and therefore adequacy of preservation is more important. 

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