Methionine-functionalized graphene oxide/sodium alginate bio-polymer nanocomposite hydrogel beads: Synthesis, isotherm and kinetic studies for an adsorptive removal of fluoroquinolone antibiotics

This work was supported by Pt. Ravishankar Research Fellowship Scheme, Raipur, Chhattisgarh, India (grant number V.R. No. 3114/4/Fin./Sch.//2018). This work was also supported by national funds through FCT-Fundacao para a Ciencia e a Tecnologia, I.P., under the Scientific Employment Stimulus-Institutional Call (CEECINST/00102/2018) and by the Associate Laboratory for Green Chemistry-LAQV, financed by national funds from FCT/MCTES (UIDB/50006/2020 and UIDP/50006/2020).In spite of the growing demand for new antibiotics, in the recent years, the occurrence of fluoroquinolone antibiotics (as a curative agent for urinary tract disorders and respiratory problems) in wastewater have drawn immense attention. Traces of antibiotic left-overs are present in the water system, causing noxious impact on human health and ecological environments, being a global concern. Our present work aims at tackling the major challenge of toxicity caused by antibiotics. This study deals with the efficient adsorption of two commonly used fluoroquinolone (FQ) antibiotics, i.e., Ofloxacin (OFX) and Moxifloxacin (MOX) on spherical hydrogel beads generated from methionine‒functionalized graphene oxide/ sodium alginate polymer (abbreviated Met-GO/SA) from aqueous solutions. The composition, morphology and crystal phase of prepared adsorbents were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM) and thermogravimetric analysis/differential thermogravimetry (TGA/DTG). Batch adsorption tests are followed to optimize the conditions required for adsorption process. Both functionalized and non-functionalized adsorbents were compared to understand the influence of several experimental parameters, such as, the solution pH, contact time, adsorbent dosage, temperature and initial concentration of OFX and MOX on adsorption. The obtained results indicated that the functionalized adsorbent (Met-GO/SA) showed a better adsorption efficiency when compared to non-functionalized (GO/SA) adsorbent. Further, the Langmuir isotherm was validated as the best fitting model to describe adsorption equilibrium and pseudo second-order-kinetic model fitted well for both types of adsorbate. The maximum adsorption capacities of Met-GO/SA were 4.11 mg/g for MOX and 3.43 mg/g for OFX. Thermodynamic parameters, i.e., ∆G°, ∆H° and ∆S° were also calculated. It was shown that the overall adsorption process was thermodynamically favorable, spontaneous and exothermic in nature. The adsorbents were successfully regenerated up to four cycles with 0.005 M NaCl solutions. Overall, our work showed that the novel Met-GO/SA nanocomposite could better contribute to the removal of MOX and OFX from the liquid media. The gel beads prepared have adequate features, such as simple handling, eco-friendliness and easy recovery. Hence, polymer gel beads are promising candidates as adsorbents for large-scale water remediation.publishersversionpublishe

Cytotoxic and cell vacuolating activity of Vibrio fluvialis isolated from paediatric patients with diarrhoea

Vibrio fluvialis is a halophilic Vibrio species associated with acute diarrhoeal illness in humans. It has the potential to cause outbreaks and has an association with paediatric diarrhoea. In this study, 11 V. fluvialis strains isolated from hospitalized patients with acute diarrhoea at the Infectious Diseases Hospital, Kolkata were extensively characterized. All the strains showed growth in peptone broth containing 7 % NaCl. The strains showed variable results in Voges-Proskauer test and to a vibriostatic agent. There was also variation in their antibiograms, and some of the strains were multidrug resistant. Among the 11 strains, two showed only a single band difference in their PFGE profile and the remaining strains showed nine different PFGE patterns. However, unlike PFGE, the strains exhibited close matches and clustering in their ribotype patterns. The haemolytic effect on sheep red blood cells varied with strains. Partial sequence analysis revealed that the V. fluvialis haemolysin gene has 81 % homology with that of the El Tor haemolysin of Vibrio cholerae. A striking finding was the capability of all the strains to evoke distinct cytotoxic and vacuolation effects on HeLa cells

Intensified elimination of aqueous heavy metal ions using chicken feathers chemically modified by a batch method

UIDB/50006/2020Modified chicken feathers (MCFs) were used as adsorbents for the removal of Co(II), Cu(II), Fe(II) and Ni(II) heavy metal ions from water by varying pH, adsorbent concentration and time. MCFs were characterized using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopic (SEM) analysis, Energy Dispersive X-ray (EDX) spectroscopy, Adsorption of N2 at −196 °C, Thermogravimetric analysis (TGA) and X-ray Diffraction (XRD) analysis. The adsorption isotherm for the metal ions could be well explained by the Langmuir model. The maximum adsorption capacities were 200.0, 50.0, 43.47, and 4.85 mg/g, following the sequence: Cu(II) > Co(II) > Fe(II) > Ni(II), respectively. Removal efficiencies of Co(II), Cu(II), Fe(II) and Ni(II) ions were 98.7%, 98.9%, 98.7% and 99%, respectively, for 20 mg/L concentration. The study of the adsorption kinetics for metal ions on MCFs confirmed that the process followed a pseudo second order kinetic model in all cases. The thermodynamics showed that the adsorption processes for metal ions adsorption on MCFs were spontaneous and endothermic. MCFs exhibited a good recyclability and high adsorption efficacy after 7 cycles using a 0.1 M EDTA solution, maintaining 90% of the adsorption ability.authorsversionpublishe

Mechanism of Drug Resistance in Clonally Related Clinical Isolates of Vibrio fluvialis Isolated in Kolkata, India

The molecular mechanisms of drug resistance in 19 strains of Vibrio fluvialis isolated from 1998 to 2002 in Kolkata, India, were investigated. Class 1 integrons were detected in eight strains, and four strains were found to carry SXT integrases. In the presence of carbonyl cyanide m-chlorophenylhydrazone or reserpine, all nalidixic acid- and ciprofloxacin-resistant strains became sensitive, suggesting that drug efflux plays a major role in quinolone resistance in V. fluvialis. It was further seen that strains which had MICs of >25 μg/ml for nalidixic acid had a sense mutation (Ser to Ile) at position 83 of the quinolone resistance-determining region of gyrA. All except one of the integron- and SXT integrase-bearing strains belonged to the same ribotype

Escalating Association of Vibrio cholerae O139 with Cholera Outbreaks in India

Between December 1999 and December 2000, teams from the National Institute of Cholera and Enteric Diseases, Calcutta, India, examined eight outbreaks of cholera, which occurred in different parts of the country distant from each other. In two of these outbreaks each, only V. cholerae O1 biotype ElTor or V. cholerae O139 could be isolated, while in the remaining four outbreaks, both O1 and O139 were isolated. The interesting feature is the escalating association of V. cholerae O139 with outbreaks of cholera; two of the most recent outbreaks, one in Calcutta and one in Orissa, were caused exclusively by O139. The O139 strains from the six different outbreaks were genotypically closely related. These trends indicate a shift in the outbreak propensity of V. cholerae O139

Assessing impact of climate change on season length in Karnataka for IPCC SRES scenarios

Citation: Anandhi, Aavudai. “Assessing Impact of Climate Change on Season Length in Karnataka for IPCC SRES Scenarios.” Journal of Earth System Science 119, no. 4 (August 2010): 447–60. https://doi.org/10.1007/s12040-010-0034-5.Changes in seasons and season length are an indicator, as well as an effect, of climate change. Seasonal change profoundly affects the balance of life in ecosystems and impacts essential human activities such as agriculture and irrigation. This study investigates the uncertainty of season length in Karnataka state, India, due to the choice of scenarios, season type and number of seasons. Based on the type of season, the monthly sequences of variables (predictors) were selected from datasets of NCEP and Canadian General Circulation Model (CGCM3). Seasonal stratifications were carried out on the selected predictors using K-means clustering technique. The results of cluster analysis revealed increase in average, wet season length in A2, A1B and B1 scenarios towards the end of 21st century. The increase in season length was higher for A2 scenario whereas it was the least for B1 scenario. COMMIT scenario did not show any change in season length. However, no change in average warm and cold season length was observed across the four scenarios considered. The number of seasons was increased from 2 to 5. The results of the analysis revealed that no distinct cluster could be obtained when the number of seasons was increased beyond three