Date Published: March 1, 2016
Publisher: Springer Berlin Heidelberg
Author(s): Kiana Alasvand Zarasvand, V. Ravishankar Rai.
To control the severe problem of microbiologically influenced corrosion, industries require highly potent antibacterial agent which can inhibit the growth of bacteria on man-made surfaces. This need drove the research towards the synthesis of nanoscale antimicrobial compounds. We, therefore, screened several bacteria for the biosynthesis of copper/copper compound nanoparticles which could inhibit the growth of Desulfovibrio marinisediminis, a sulfate reducing bacterium. Supernatant of thirty bacteria isolated from the biofilm formed on ship hull was mixed with 1 mM CuCl2 solution at room temperature. Eight bacterial strains, whose mixtures exhibited colour change, were selected for antimicrobial test. One nanoparticle which has been biosynthesized by Shewanella indica inhibited the growth of D. marinisediminis. Characterization of this particle by UV–visible spectrophotometer, XRD, TEM, DLS and FTIR showed that the particle is polydisperse CuO nanoparticle with average size of 400 nm.
Paint and coating industries get the benefit by the use of NP to reduce corrosion. Addition of NP modifies morphology, conductivity and different physical properties of coats and provides superior resistance against metal corrosion (Montemor 2014). Microorganisms have an important role in corrosion. They cause rapid and severe type of corrosion failure which is well documented by many industries including shipping industry, offshore oil and gas production, power plants and coastal industrial plants (Licina and Cubicciotti 1989; Bodtker et al. 2008; Inbakandan et al. 2010). To manage microbial corrosion, nano-scale materials such as nanosilver and nanotitanium dioxide with potent antimicrobial activity are used to inhibit the microbial growth (Yu et al. 2003; Naik and Kowshik 2014). Copper and copper oxides are other nanoparticles possessing high toxicity. Their toxic effect found to be due to generation of reactive oxygen species, lipid peroxidation, protein oxidation and DNA degradation in the bacterial cells (Chatterjee et al. 2014).
Industries use chemicals, mainly biocides to mitigate microbial corrosion. However, due to the emergence of bacterial resistance, they tend to look for alternative antimicrobial agents. Interest in the application of nano-sized antimicrobial compounds is on the increase. Nano-sized materials have higher antimicrobial properties as compared to the bulky ones because by decreasing the dimension of the compounds, the surface to volume ratio will get increased and this property augments their interaction with bacterial cell membrane (Hajipour et al. 2012). Though these compounds have good antimicrobial activity, they can be synthesized by Microorganism. Bacteria can very well be used as nanofactories. Biosynthesis of nanoparticles by microorganisms has been attributed to energy production, special functions and detoxification of heavy metals (Krumov et al. 2009). Ramanathan et al. (2013) hypothesised that Morganella sp., a silver-resistant bacterium with ability to biosynthesis silver NP, is able to produce copper NP because proteins responsible for bacterial resistant to silver and copper were highly similar. This bacterium was able to produce spherical copper/copper oxide NP with the size of 7–15 nm. Although there are some reports regarding the biosynthesis of copper and its oxide by Escherichia coli, Morganella morganii and Pseudomonas stutzeri, the exploitation of bacteria as biological resource material for synthesis of Copper NP needs further explorations (Singh et al. 2010; Varshney et al. 2010; Ramanathan et al. 2013). In the present study, we isolated bacteria from the biofilm (an environment where vast diversity of bacteria live in packed community) formed on corroded ship hull which was covered with paint containing copper. Initially, bacteria have been screened for the synthesis of nanoparticles. After adding bacterial supernatant with CuCl2 solution, colour change from light yellow to light brown was observed in eight mixtures. This colour change is the primary indicator for the synthesis of CuONP.
Use of nano-antimicrobial compound to control biocorrosion is an attractive option for industry because of its high biocidal activity. These particles could be synthesized by physical, chemical and biological methods. As the biological method is eco-friendly, it has got profound interest compared to other methods. In the present study, extracellular synthesis of polydispersed CuONP with average size of 400 nm by S. indica strain has been reported. These NP have the ability to inhibit the growth of metal corrosion causing bacteria, D. marinisedimins. With our finding and earlier report on ability of Shewanella biofilm in inhibition of copper corrosion, it seems reasonable to protect copper from MIC by Shewanella live biofilm (Kusa et al. 2006). The advantage of this process as compared to adding nanoparticle to paint is that the nanoparticles do not leach out of biofilm and kill only those bacteria that contact the biofilm.