Biocidal effect of cathodic protection on bacterial viability in biofilm attached to carbon steel

Department of Bioengineering, Tokyo Institute of Technology 4259 J2-15 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Biotechnology and Bioengineering (Impact Factor: 4.13). 07/2007; 97(4):850-7. DOI: 10.1002/bit.21278
Source: PubMed


Biofilm formed on carbon steel by various species of bacterial cells causes serious problems such as corrosion of steel, choking of flow in the pipe, deterioration of the heat-transfer efficiency, and so on. Cathodic protection is known to be a reliable method for protecting carbon steel from corrosion. However, the initial attachment of bacteria to the surface and the effects of cathodic protection on bacterial viability in the biofilm have not been clarified. In this study, cathodic protection was applied to an artificial biofilm containing Pseudomonas aeruginosa (PAO1), a biofilm constituent, on carbon steel. The aims of this study were to evaluate the inhibition effect of cathodic protection on biofilm formation and to reveal the inhibition mechanisms. The viability of PAO1 in artificial biofilm of 5 mm thickness on cathodically protected steel decreased to 1% of the initial cell concentration. Analysis of pH distribution in the artificial biofilm by pH microelectrode revealed that pH in proximity to carbon steel increased to approximately 11 after cathodic protection for 5 h. Moreover, 99% of region in the artificial biofilm was under the pH conditions of over nine. A simulation of pH profile was shown to correspond to experimental values. These results indicate cells in the artificial biofilm were killed or damaged by cathodic protection due to pH increase.

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    • "Settlement of C. rubrum Papers dealing with colonisation on polarised substrata represent a small fraction of the literature on the colonisation of artificial substrata. In particular, several investigations have been performed in order to (i) prevent (antifouling technologies) (Nakasono et al. 1993; Wellman et al. 1996; Miyanaga et al. 2007), (ii) stimulate (restoration strategies) the development of benthic organisms (Hilbertz 1979; Schuhmacher and Shillak 1994; Sternhell et al. 2002; Goreau et al. 2004; Sabater and Yap 2004), and (iii) evaluate the effect of colonisation on cathodic protection (Edyvean et al. 1992; Dexter and Lin 1992; De Saravia et al. 1997; Eashwar et al. 2009). To the authors' knowledge, no studies have been carried out on settlement of octocorals on artificially polarised substrata. "
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    • "Alternatively, protective antifouling coatings, such as tributyltin (TBT)-based paints, are used extensively in seawater environments, despite concerns for their toxicity, to combat biofouling and biocorrosion of metallic materials (Jelic-Mrcelic et al., 2006; Yebra et al., 2004). Although cathodic protection has been reported to effectively inhibit biocorrosion of SS by aerobic bacteria (Guezennec, 1994; Miyanaga et al., 2007), it has been found to have no effect on the adhesion of anaerobic bacteria, and is thus unable to prevent the initiation of pitting corrosion by SRB (de Mele et al., 1995). In view of environmental, ecological, and economical impacts, more recent efforts are focused on developing environmentally benign antimicrobial coatings to prevent bacterial adhesion and biofilm formation (Al- Darbi et al., 2002; Sreekumari et al., 2005; Telegdi et al., 2005), as the formation of biofilms is widely recognized as the key step in initiating biocorrosion. "
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    • "The literature on the interrelationship between cathodic polarization and biofilms, as stated by Little et al. (1999) is rather confusing. Some authors (eg Guezennec 1991; Nekoksa and Gutherman 1991) have reported more bacterial settlement on cathodically protected metals than unpolarized ones, whereas others (eg Videla et al. 1993; Miyanaga et al. 2007) have reported the reverse. Maxwell (1986) did not find variations in biofilm bacterial numbers, but measured reduction of metabolic activity during cathodic polarization . "
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