Punniyakotti Parthipan

Biosurfactant and Degradative Enzymes Mediated Crude Oil Degradation by Bacterium Bacillus subtilis A1

In this work, the biodegradation of the crude oil by the potential biosurfactant producing Bacillus subtilis A1 was investigated. The isolate had the ability to synthesize degradative enzymes such as alkane hydroxylase and alcohol dehydrogenase at the time of biodegradation of hydrocarbon. The biosurfactant producing conditions were optimized as pH 7.0, temperature 40°C, 2% sucrose and 3% of yeast extract as best carbon and nitrogen sources for maximum production of biosurfactant (4.85 g l-1). Specifically, the low molecular weight compounds, i.e., C10–C14 were completely degraded, while C15–C19 were degraded up to 97% from the total hydrocarbon pools. Overall crude oil degradation efficiency of the strain A1 was about 87% within a short period of time (7 days). The accumulated biosurfactant from the biodegradation medium was characterized to be lipopeptide in nature. The strain A1 was found to be more robust than other reported biosurfactant producing bacteria in degradation efficiency of crude oil due to their enzyme production capability and therefore can be used to remove the hydrocarbon pollutants from contaminated environment.

Airborne bacteria associated with corrosion of mild steel 1010 and aluminum alloy 1100

A novel approach to measure the contribution of airborne bacteria on corrosion effects of mild steel (MS) and aluminum alloy (AA) as a function of their exposure period, and the atmospheric chemical composition was investigated at an urban industrial coastal site, Singapore. The 16S rRNA and phylogenetic analyses showed that Firmicutes are the predominant bacteria detected in AA and MS samples. The dominant bacterial groups identified were Bacillaceae, Staphylococcaceae, and Paenibacillaceae. The growth and proliferation of these bacteria could be due to the presence of humidity and chemical pollutants in the atmosphere, leading to corrosion. Weight loss showed stronger corrosion resistance of AA (1.37xa0mg/cm2) than MS (26.13xa0mg/cm2) over the exposure period of 150xa0days. The higher corrosion rate could be a result of simultaneous action of pollutants and bacterial exopolysaccharides on the metal surfaces. This study demonstrates the significant involvement of airborne bacteria on atmospheric corrosion of engineering materials.

Biocorrosion and Its Impact on Carbon Steel API 5LX by Bacillus subtilis A1 and Bacillus cereus A4 Isolated From Indian Crude Oil Reservoir

Biocorrosion is a frequent problem in oil and gas industry that occurs due to the ubiquitous nature of the microorganisms. The main objective of this study is to identify corrosive bacterial strains from crude oil reservoir samples and elucidation of their role in the biocorrosion of carbon steel API 5LX. Pure bacterial strains were identified using both biochemical and 16S rRNA gene sequencing methods. Identified dominant strains were subjected to weight loss and electrochemical studies. The Gram-positive bacteria Bacillus subtilis A1 and Bacillus cereus A4 were identified as dominant species. Corrosion rates were 0.743, 0.594 and 0.297xa0mm/year in the presence of strain B. subtilis A1, B. cereus A4 and abiotic control system, respectively. The charge transfer resistance values show a continuous decrease in the presence of bacterial culture indicating that formation of the heterogeneous biofilm and iron oxide over the metal surface leads to the corrosion phenomenon. Surface analysis techniques including X-ray diffraction, scanning electron microscopy and atomic force microscopy examination reveal the ability of bacteria to oxidize iron/manganese to their corresponding oxides, leading to the formation of thick biofilm on metal surface and accelerating the pitting corrosion of carbon steel.

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.

Electrochemical decolorization of methyl red by RuO2-IrO2-TiO2 electrode and biodegradation with Pseudomonas stutzeri MN1 and Acinetobacter baumannii MN3: An integrated approach

Textile effluent consists of enormous quantities of toxic dyes, which are being discharged into natural aqueous system and thus contaminate the water quality. Hence it is important to develop an eco-friendly and cost effective technology to treat the dyes contaminated wastewater. In this research, an integrated approach of electrochemical oxidation (EO) and biodegradation process (BP) was studied of methyl red (MR) dye. In EO, RuO2-IrO2-TiO2 is used as anode and titanium mesh electrode as cathode. This was followed by BP of the treated EO effluent. Various parameters viz., pH (5-10), sodium chloride concentrations (NaCl) (1-5xa0gxa0L-1) and current density (10-30xa0mAxa0cm2) were optimized. The results of the EO showed 99.96% of MR decolorization within 10xa0minxa0at pH of 5, NaCl of 2xa0gxa0L-1 and current density of 30xa0mAxa0cm2. The EO treated MR was further treated by BP Pseudomonas stutzeri MN1, Acinetobacter baumannii MN3 and mixed consortia of MN1 and MN3. The out of three treatments, the results of mixed consortium BP showed 90% removal of COD at the end of 24xa0h. The phytotoxic evaluation using Vigna radiata seeds confirmed the toxicity of untreated MR solution, whereas, 100% germination was observed in treated (biodegraded) MR solution. Overall these results evidenced that MR dye was completely decolorized and mineralized by EO and BP within 10xa0min and 24xa0h respectively. Hence, this integrated approach can be used as an effective degradation method to treat dyes in the textile industry.

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

Biosurfactant and enzyme mediated crude oil degradation by Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3

The present study focuses on the optimization of biosurfactant (BS) production using two potential biosurfactant producer Pseudomonas stutzeri NA3 and Acinetobacter baumannii MN3 and role of enzymes in the biodegradation of crude oil. The optimal conditions for P. stutzeri NA3 and A. baumannii MN3 for biodegradation were pH of 8 and 7; temperature of 30 and 40xa0°C, respectively. P. stutzeri NA3 and A. baumannii MN3 produced 3.81 and 4.68xa0g/L of BS, respectively. Gas chromatography mass spectrometry confirmed that BS was mainly composed of fatty acids. Furthermore, the role of the degradative enzymes, alkane hydroxylase, alcohol dehydrogenase and laccase on biodegradation of crude oil are explained. Maximum biodegradation efficiency (BE) was recorded for mixed consortia (86%) followed by strain P. stutzeri NA3 (84%). Both bacterial strains were found to be vigorous biodegraders of crude oil than other biosurfactant-producing bacteria due to their enzyme production capabilities and our results suggests that the bacterial isolates can be used for effective degradation of crude oil within short time periods.

Biosurfactants produced by Bacillus subtilis A1 and Pseudomonas stutzeri NA3 reduce longevity and fecundity of Anopheles stephensi and show high toxicity against young instars

Anopheles stephensi acts as vector of Plasmodium parasites, which are responsible for malaria in tropical and subtropical areas worldwide. Currently, malaria management is a big challenge due to the presence of insecticide-resistant strains as well as to the development of Plasmodium species highly resistant to major antimalarial drugs. Therefore, the present study focused on biosurfactant produced by two bacteria Bacillus subtilis A1 and Pseudomonas stutzeri NA3, evaluating them for insecticidal applications against malaria mosquitoes. The produced biosurfactants were characterized using FT-IR spectroscopy and gas chromatography-mass spectrometry (GC-MS), which confirmed that biosurfactants had a lipopeptidic nature. Both biosurfactants were tested against larvae and pupae of A. stephensi. LC50 values were 3.58 (larva I), 4.92 (II), 5.73 (III), 7.10 (IV), and 7.99 (pupae) and 2.61 (I), 3.68 (II), 4.48 (III), 5.55 (IV), and 6.99 (pupa) for biosurfactants produced by B. subtilis A1 and P. stutzeri NA3, respectively. Treatments with bacterial surfactants led to various physiological changes including longer pupal duration, shorter adult oviposition period, and reduced longevity and fecundity. To the best of our knowledge, there are really limited reports on the mosquitocidal and physiological effects due to biosurfactant produced by bacterial strains. Overall, the toxic activity of these biosurfactant on all young instars of A. stephensi, as well as their major impact on adult longevity and fecundity, allows their further consideration for the development of insecticides in the fight against malaria mosquitoes.

Enzyme-mediated biodegradation of long-chain n -alkanes (C 32 and C 40 ) by thermophilic bacteria

Abstract Removal of long-chain hydrocarbons and n-alkanes from oil-contaminated environments are mere important to reduce the ecological damages, while bio-augmentation is a very promising technology that requires highly efficient microbes. In present study, the efficiency of pure isolates, i.e., Geobacillus thermoparaffinivorans IR2, Geobacillus stearothermophillus IR4 and Bacillus licheniformis MN6 and mixed consortium on degradation of long-chain n-alkanes C32 and C40 was investigated by batch cultivation test. Biodegradation efficiencies were found high for C32 by mixed consortium (90%) than pure strains, while the pure strains were better in degradation of C40 than mixed consortium (87%). In contrast, the maximum alkane hydroxylase activities (161xa0µmolxa0mg−1 protein) were recorded in mixed consortium system that had supplied with C40 as sole carbon source. Also, the alcohol dehydrogenase (71xa0µmolxa0mg−1 protein) and lipase activity (57xa0µmolxa0mg−1 protein) were found high. Along with the enzyme activities, the hydrophobicity natures of the bacterial strains were found to determine the degradation efficiency of the hydrocarbons. Thus, the study suggested that the hydrophobicity of the bacteria is a critical parameter to understand the biodegradation of n-alkanes.