Jayaraman Narenkumar

Role of Bacterial Plasmid on Biofilm Formation and Its Influence on Corrosion of Engineering Materials

Bacterial plasmids are involved in biofilm formation, degradation of hydrocarbons and biosynthesis of antibiotics in extreme environments. A number of intercalating compounds have been reported to be used for curing the plasmids in various bacterial species, since they act as inhibitors during plasmid replication by selectively binding to the plasmid DNA. In this research, we investigated the influence of bacterial plasmid on biofilm formation on metal surface and corrosion of engineering metals, such as mild steel (MS), stainless steel (SS) and brass (BS). The biocorrosion behaviour of Bacillus thuringiensis EN2 wild and cured strain was studied using immersion tests based on the weight loss method, electrochemical analysis and surface analysis techniques (FTIR spectroscopy). The plasmid cured strain EN2 was unable to form biofilm, showing significantly less corrosion over all the tested metal surfaces. On the contrary, the presence of plasmid led to higher corrosion rate (0.18, 10.3 and 91.5xa0mm/year) and surface hydrophobicity for MS, SS and BS. Overall, it can be concluded that the plasmid gene was found to be responsible for the biofilm formation, which determines the corrosion rate of metals.

Ginger extract as green biocide to control microbial corrosion of mild steel

In latest years, various techniques and chemicals have been used for the control of microbial influenced corrosion (MIC) of metals. The application of botanical-based biocides is one of the effective and practical techniques in the fight against MIC. In the present study, the role of aqueous extract of ginger (Zingiber officinale) (GIE) as green biocide to control MIC of mild steel 1010 (MS) in a cooling water system was investigated. Biocorrosion behavior of Bacillus thuringiensis EN2 on MS and its control by GIE was analyzed by electrochemical measurements. Polarization, electrochemical studies (ES), weight loss measurements (WL), and surface analysis (XRD, X-ray diffraction spectroscopy, and FTIR, Fourier transform infra-red spectroscopy) were performed under various incubation periods up to 4xa0weeks. We observed that EN2 forms a thick biofilm on the MS metal surface at the end of the incubation period and the WL significantly increased to 993xa0mg at fourth week when compared to the initial immersion period (194xa0±xa02xa0mg). In contrast, with addition of GIE, WL was reduced about 41xa0±xa02xa0mg over biotic system (993xa0±xa02xa0mg). GC–MS analysis confirmed the adsorption of active component of GIE (β-turmerone) on the metal surface as a protective layer to prevent the biofilm formation and thus leads to reduction of corrosion. The optimum 20xa0ppm of GIE was found to be effective corrosion inhibition efficiency which was about 80%. From the results of WL, ES, XRD, FTIR, and GC–MS, GIE was identified as biocide and thus inhibits the bacterial growth on MS metal surface and it leads to control MIC. XRD showed that the GIE with EN2 resulted in less formation of corrosion products over biotic and abiotic systems. Overall, this research first shed light on the antibacterial activity of GIE inhibiting biofilm formation, thus reducing the corrosion of MS in cooling water systems.

Influence of Thermophilic Bacteria on Corrosion of Carbon Steel in Hyper Chloride Environment

The present study evaluates, the oxidation behaviour of thermophilic bacteria Geobacillus thermoparaffinivorans IR2, Geobacillus stearothermophillus IR4 and Bacillus licheniformis MN6 on carbon steel API 5 LX by weight loss, electrochemical studies (impedance and polarization analysis) and surface analysis (X-ray diffraction spectroscopy). The presence of IR2, IR4 and MN6 showed highest corrosion rate (CR) of 2.51, 2.82 and 2.41xa0mm/year, respectively, than the abiotic control (0.95xa0mm/year). Whereas in the presence of biocide tetrakis (hydroxymethyl) phosphonium sulphate (THPS) inhibition of the biofilm formation was noticed on the carbon steel and thus reduced the CR of about 0.36, 0.46 and 0.42xa0mm/year. The electrochemical studies also revealed that higher charge transfer resistance (105xa0Ωxa0cm2) and solution resistance (6.99xa0Ωxa0cm2) in the presence of THPS due to the intact protective film on carbon steel surface. Thus, THPS is found to act as an effective candidate towards control microbial influenced corrosion by thermophilic bacteria on carbon steel API5LX in a 36% chloride environment.

Bioengineered silver nanoparticles as potent anti-corrosive inhibitor for mild steel in cooling towers

AbstractSilver nanoparticle-aided enhancement in the anti-corrosion potential and stability of plant extract as ecologically benign alternative for microbially induced corrosion treatment is demonstrated. Bioengineered silver nanoparticles (AgNPs) surface functionalized with plant extract material (proteinacious) was generated in vitro in a test tube by treating ionic AgNO3 with the leaf extract of Azadirachta indica that acted as dual reducing as well as stabilizing agent. Purity and crystallinity of the AgNPs, along with physical and surface characterizations, were evaluated by performing transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive x-ray spectra, single-area electron diffractions, zeta potential, and dynamic light scattering measurements. Anti-corrosion studies against mild steel (MS1010) by corrosion-inducive bacterium, Bacillus thuringiensis EN2 isolated from cooling towers, were evaluated by performing electrochemical impedance spectroscopy (EIS), weight loss analysis, and surface analysis by infrared spectroscopy. Our studies revealed that AgNPs profoundly inhibited the biofilm on MS1010 surface and reduced the corrosion rates with the CR of 0.5xa0mm/y and an inhibition efficiency of 77% when compared to plant extract alone with a CR of 2.2xa0mm/y and an inhibition efficiency of 52%. Further surface analysis by infrared spectra revealed that AgNPs formed a protective layer of self-assembled film on the surface of MS1010. Additionally, EIS and surface analysis revealed that the AgNPs have inhibited the bacterial biofilm and reduced the pit on MS1010. This is the first report disclosing the application of bioengineered AgNP formulations as potent anti-corrosive inhibitor upon forming a protective layer over mild steel in cooling water towers.n Graphical Abstractᅟ

Control of corrosive bacterial community by bronopol in industrial water system

Ten aerobic corrosive bacterial strains were isolated from a cooling tower water system (CWS) which were identified based on the biochemical characterization and 16S rRNA gene sequencing. Out of them, dominant corrosion-causing bacteria, namely, Bacillus thuringiensis EN2, Terribacillus aidingensis EN3, and Bacillus oleronius EN9, were selected for biocorrosion studies on mild steel 1010 (MS) in a CWS. The biocorrosion behaviour of EN2, EN3, and EN9 strains was studied using immersion test (weight loss method), electrochemical analysis, and surface analysis.xa0To address the corrosion problems, an anti-corrosive study using a biocide, bronopol was also demonstrated. Scanning electron microscopy and Fourier-transform infrared spectroscopy analyses of the MS coupons with biofilm developed after exposure to CWS confirmed the accumulation of extracellular polymeric substances and revealed that biofilms was formed as microcolonies, which subsequently cause pitting corrosion. In contrast, the biocide system, no pitting type of corrosion, was observed and weight loss was reduced about 32xa0±xa02xa0mg over biotic system (286xa0±xa02xa0mg). FTIR results confirmed the adsorption of bronopol on the MS metal surface as protective layer (co-ordination of NH2–Fe3+) to prevent the biofilm formation and inhibit the corrosive chemical compounds and thus led to reduction of corrosion rate (10xa0±xa01xa0mm/year). Overall, the results from WL, EIS, SEM, XRD, and FTIR concluded that bronopol was identified as effective biocide and corrosion inhibitor which controls the both chemical and biocorrosion of MS in CWS.Graphical Abstract

Role of calcium-depositing bacteria Agrobacterium tumefaciens and its influence on corrosion of different engineering metals used in cooling water system

The present investigation deals with the role of calcium-depositing bacterial community on corrosion of various engineering metals, namely, brass alloy (BS), copper (Cu), stainless steel (SS) and mild steel (MS). Based on the corrosion behavior, Agrobacterium tumefaciens EN13, an aerobic bacterium is identified as calcium-depositing bacteria on engineering metals. The results of the study are supported with biochemical characterization, 16S rRNA gene sequencing, calcium quantification, weight loss, electrochemical (impedance and polarization) and surface analysis (XRD and FTIR) studies. The calcium quantification study showed carbonate precipitation in abiotic system/biotic system as 50 and 700xa0ppm, respectively. FTIR results too confirmed the accumulation of calcium deposits from the environment on the metal surface by EN13. Electrochemical studies too supported the corrosion mechanism by showing a significant increase in the charge transfer resistance (Rct) of abiotic system (44, 33.6, 45, 29.6xa0Ωxa0cm2) than compared to biotic system (41, 10.1 29 and 25xa0Ωxa0cm2). Hence, the outcome of the present study confirmed the enhanced bioaccumulation behavior of calcium by the strain, EN13.

Treatment of soak liquor and bioelectricity generation in dual chamber microbial fuel cell

The discharge of untreated soak liquor from tannery industry causes severe environmental pollution. This study is characterizing the soak liquor as a substrate in the microbial fuel cell (MFC) for remediation along with electricity generation. The dual chamber MFC was constructed and operated. Potassium permanganate was used as cathode solution and carbon felt electrode as anodic and cathodic material, respectively. The soak liquor was characterized by electrochemical studies viz., cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and polarization studies, respectively. The removal percentage of protein, lipid, and chemical oxygen demand (COD) were measured before and after treatment with MFC. The results of MFC showed a highest current density of 300xa0mA/cm2 and a power density of 92xa0mW/m2. The removal of COD, protein, and lipid were noted as 96, 81, and 97% respectively during MFC process. This MFC can be used in tannery industries for treating soak liquor and simultaneous electricity generation.

Biocorrosion of mild steel and copper used in cooling tower water and its control

The present study describes the biocorrosion of mild steel (MS1010) and pure copper (Cu) in cooling water environments (both field and lab study). Electrochemical and surface analyses of both metals were carried out to confirm the corrosion susceptibility in the presence of bacteria and inhibitor. Surface analysis of the MS and Cu coupons revealed that biofilm was developed with increasing exposure time in the field study. In the lab study, accumulation of extracellular polymeric substance over the metal surface was noticed and led to the severe pitting type of corrosion on both metal surfaces. Besides, the anti-corrosive study was carried out using the combinations of commercial corrosion inhibitor (S7653—10xa0ppm) with biocide (F5100—5xa0ppm), and the results reveal that the corrosion rate of MS and Cu was highly reduced to 0.0281 and 0.0021xa0mm/year (inhibitor system) than 0.1589 and 0.0177xa0mm/year (control system). Inhibition efficiency for both metals in the presence of inhibitor with biocide was found as 82 and 88% for MS and Cu, respectively. The present study concluded that MS was very susceptible to biocorrosion, compared to copper metal in cooling water environment. Further, the combination of the both inhibitor and biocide was effectively inhibiting the biocorrosion which was due to its antibacterial and anti-corrosive properties.