Faculty Publications
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Item Chromium-resistant bacteria and their environmental condition for hexavalent chromium removal: A review(2013) Narayani, M.; Shetty K, K.The anthropogenic inputs of hexavalent chromium [Cr(VI)] have increased enormously during the past few decades and has become a challenge for life on earth and hence removal of this carcinogen has become the need of the hour. Cr(VI) removal through common physicochemical techniques is highly expensive and inappropriate at low concentration. Microbial reduction of Cr(VI) to trivalent form is considered a favorable technique for Cr(VI) removal from wastewater, as it reduces the highly toxic form of Cr to less toxic form and therefore the article conveys essential fundamental information on removal of Cr(VI) by bacteria. For efficient bioremoval of Cr(VI),the main machinery of the process, the microbes, and their conditions, which decide the fate of this heavy metal, should be appropriate. Hence, the authors cover vast information about the isolation of chromium-resistant bacteria from various environment and their Cr(VI) resistance capability. An extensive report is given on information pertaining to the factors such as cell density, pH, temperature, salt concentration, oxidation-reduction potential, electron donor, oxyanions, metabolic inhibitors, and other heavy metals that influence or affect the efficient Cr(VI) removal. Cr(VI) removal by immobilized bacterial cells and their advantages has also been summarized. In transferring this technology from laboratory to a large-scale application, better understanding of all these aspects is necessary. Hence, this developing biotechnological method that encompasses fields from genetic engineering to reactor engineering demands focused research in these directions, which may lead to implementation of this technology on a larger scale and drive it toward being the most opted-for technology. © 2013 Copyright Taylor and Francis Group, LLC.Item Role of catalyst supports in biocatalysis(John Wiley and Sons Ltd, 2023) Manikandan, S.K.; Giannakoudakis, D.A.; Prekodravac, J.R.; Nair, V.; Colmenares, J.C.Biocatalysis utilizes enzymes and microbial cells as catalysts for a wide range of applications in biotechnology. Immobilization of biocatalysts on various materials has several advantages, including the capacity for reuse, quick reaction termination, easy biocatalyst recovery and operational stability. The present article focuses on the use of material supports for developing immobilized biocatalysts in applications related to energy, environment and chemical synthesis. The work provides a comprehensive overview of a broad class of materials, including organic, inorganic and composites, that have been shown to be prosperous candidates to support the immobilization of enzymes and microbial cells. It also highlights the properties of nanomaterial support such as large surface area and comfort compartment for immobilization. The availability of different types of materials as catalyst support provides an opportunity to understand and develop efficient biocatalytic systems. The choice of selecting a catalyst support will mostly depend on the interaction of the material with the enzyme or microbial cell. Finally, potential challenges, future approaches in developing immobilized biocatalytic systems for various applications and novel material supports are suggested. © 2022 Society of Chemical Industry (SCI). © 2022 Society of Chemical Industry (SCI).Item Effective Usage of Biochar and Microorganisms for the Removal of Heavy Metal Ions and Pesticides(MDPI, 2023) Manikandan, S.K.; Pallavi, P.; Shetty K, V.; Bhattacharjee, D.; Giannakoudakis, D.A.; Katsoyiannis, I.A.; Nair, V.The bioremediation of heavy metal ions and pesticides is both cost-effective and environmentally friendly. Microbial remediation is considered superior to conventional abiotic remediation processes, due to its cost-effectiveness, decrement of biological and chemical sludge, selectivity toward specific metal ions, and high removal efficiency in dilute effluents. Immobilization technology using biochar as a carrier is one important approach for advancing microbial remediation. This article provides an overview of biochar-based materials, including their design and production strategies, physicochemical properties, and applications as adsorbents and support for microorganisms. Microorganisms that can cope with the various heavy metal ions and/or pesticides that enter the environment are also outlined in this review. Pesticide and heavy metal bioremediation can be influenced by microbial activity, pollutant bioavailability, and environmental factors, such as pH and temperature. Furthermore, by elucidating the interaction mechanisms, this paper summarizes the microbe-mediated remediation of heavy metals and pesticides. In this review, we also compile and discuss those works focusing on the study of various bioremediation strategies utilizing biochar and microorganisms and how the immobilized bacteria on biochar contribute to the improvement of bioremediation strategies. There is also a summary of the sources and harmful effects of pesticides and heavy metals. Finally, based on the research described above, this study outlines the future scope of this field. © 2023 by the authors.Item Performance of pulsed plate bioreactor for biodegradation of phenol(2007) Shetty K, K.V.; Kalifathulla, I.; Srinikethan, G.Biodegradation of phenol was carried out using Nocardia hydrocarbonoxydans immobilised on glass beads, in a pulsed plate bioreactor. The effect of operating parameters like frequency of pulsation and amplitude of pulsation on the performance of pulsed plate bioreactor for biodegradation of phenol in a synthetic wastewater containing 500 ppm phenol was studied. Axial concentration profile measurements revealed that the pulsed plate bioreactor shows continuous stirred tank behaviour. As the amplitude was increased, percentage degradation increased, reaching 100% at amplitude of 4.7 cm and higher. Introduction of pulsation is found to increase the percentage degradation. Percentage degradation has increased with increase in frequency and 100% degradation was achieved at 0.5 s-1 and above. Biofilms developed in a non-pulsed bioreactor were thicker than those in the pulsed plate bioreactor. But biofilm thickness remained almost constant with increasing frequency. Biofilm density was found to be influenced by pulsation. The time required to reach steady state was more for pulsed reactor than the non-pulsed reactor and this start-up time had increased with increase in frequency of pulsation. The performance studies reveal that the pulsed plate bioreactor with immobilized cells has the potential to be an efficient bioreactor for wastewater treatment. © 2006 Elsevier B.V. All rights reserved.Item Biological phenol removal using immobilized cells in a pulsed plate bioreactor: Effect of dilution rate and influent phenol concentration(2007) Shetty K, K.V.; Ramanjaneyulu, R.; Srinikethan, G.The continuous aerobic biodegradation of phenol in synthetic wastewater was carried out using Nocardia hydrocarbonoxydans immobilized over glass beads packed between the plates in a pulsed plate bioreactor at a frequency of pulsation of 0.5 s-1 and amplitude of 4.7 cm. The influence of dilution rate and influent phenol concentration on start up and steady state performance of the bioreactor was studied. The time taken to reach steady state has increased with increase in dilution rate and influent phenol concentration. It was found that, as the dilution rate is increased, the percentage degradation has decreased. Steady state percentage degradation was also reduced with increased influent phenol concentration. Almost 100% degradation of 300 and 500 ppm influent phenol could be achieved at a dilution rate of 0.4094 h-1 and more than 99% degradation could be achieved with higher dilution rates. At a higher dilution rate of 1.0235 h-1 and at concentrations of 800 and 900 ppm the percentage degradation has reduced to around 94% and 93%, respectively. The attached biomass dry weight, biofilm thickness and biofilm density at steady state were influenced by influent phenol concentration and dilution rate. © 2007 Elsevier B.V. All rights reserved.Item Biological sulfide oxidation using autotrophic Thiobacillus sp.: Evaluation of different immobilization methods and bioreactors(2009) Ravichandra, P.; Gopal, M.; Jetty, A.Aims: Evaluation of various immobilization methods and bioreactors for sulfide oxidation using Thiobacillus sp. was studied. Methods and Results: Ca-alginate, K-carrageenan and agar gel matrices (entrapment) and polyurethane foam and granular activated carbon (adsorption) efficacy was tested for the sulfide oxidation and biomass leakage using immobilized Thiobacillus sp. Maximum sulfide oxidation of 96% was achieved with alginate matrix followed by K-carrageenan (88%). Different parameters viz. alginate concentration (1%, 2%, 3%, 4% and 5%), CaCl2 concentration (1%, 2%, 3%, 4% and 5%), bead diameter (1, 2, 3, 4 and 5 mm), and curing time (1, 3, 6, 12 and 18 h) were studied for optimal immobilization conditions. Repeated batch experiments were carried out to test reusability of Ca-alginate immobilized beads for sulfide oxidation in stirred tank reactor and fluidized bed reactor (FBR) at different sulfide concentrations. Conclusions: The results proved to be promising for sulfide oxidation using Ca-alginate gel matrix immobilized Thiobacillus sp. for better sulfide oxidation with less biomass leakage. Significance and Impact of the Study: Biological sulfide oxidation is gaining more importance because of its simple operation. Present investigations will help in successful design and operation of pilot and industrial level FBR for sulfide oxidation. © 2009 The Society for Applied Microbiology.Item Adsorption of phenol on granular activated carbon from nutrient medium: Equilibrium and kinetic Study(2009) Dabhade, M.A.; Saidutta, M.B.; Murthy, D.V.R.This paper presents the adsorption of phenol on granular activated carbon (GAC) from nutrient medium suitable for microorganisms' growth and also the subsequent biodegradation. Two parameter Langmuir and Freundlich adsorption isotherm models were studied using large range of phenol concentration (50-1000 mg/L). In low range of phenol concentration (50-300 mg/L), correlation coefficient, normalized deviation "g% and separation factor were 0.9989,2.18% and 0.38-0.78 respectively, while for higher concentration range (400-1000 mg/L), the corresponding values were 0.9719, 1.9% and 0.45- 0.67. Freundlich isotherm gave correlation coefficient of 0.9984, 1/n. value of 0.7269 and normalized deviation of 4.55%. Comparison based on R2, adjusted R2, normalized deviation and root mean square deviation (RMSD) showed that the Redke-Prausnitz isotherm model gives better prediction compared to other models. Adsorption of phenol follows pseudo second order kinetics with correlation coefficient closer to one. Biodegradation study using immobilized cells of Nocardia hydrocarbonoxydans on GAC showed that, biodegradation begins well before GAC reaches the saturation period.Item Experimental investigation and artificial neural network-based modeling of batch reduction of hexavalent chromium by immobilized cells of newly isolated strain of chromium-resistant bacteria(2012) Shetty K, K.V.; Namitha, L.; Rao, S.N.; Narayani, M.The batch bioreduction of Cr(VI) by the cells of newly isolated chromium-resistant Acinetobacter sp. bacteria, immobilized on glass beads and Ca-alginate beads, was investigated. The rate of reduction and percentage reduction of Cr(VI) decrease with the increase in initial Cr(VI) concentration, indicating the inhibitory effect of Cr(VI). Efficiency of bioreduction can be improved by increasing the bioparticle loading or the initial biomass loading. Glass bioparticles have shown better performance as compared to Ca-alginate bioparticles in terms of batch Cr(VI) reduction achieved and the rate of reduction. Glass beads may be considered as better cell carrier particles for immobilization as compared to Ca-alginate beads. Around 90% reduction of 80 ppm Cr(VI) could be achieved after 24 h with initial biomass loading of 14.6 mg on glass beads. Artificial neural networkbased models are developed for prediction of batch Cr(VI) bioreduction using the cells immobilized on glass and Ca-alginate beads. © Springer Science+Business Media B.V. 2011.Item Microbial disinfection of water with endotoxin degradation by photocatalysis using Ag@TiO2 core shell nanoparticles(Springer Verlag service@springer.de, 2016) Sreeja, S.; Shetty K, K.V.The studies on photocatalytic disinfection of water contaminated with Escherichia coli using Ag core and TiO2 shell (Ag@TiO2) nanoparticles under UV irradiation showed that these nanoparticles are very efficient in water disinfection both in their free and immobilised form. Complete disinfection of 40 × 108 CFU/mL could be achieved in 60 min with 0.4 g/L catalyst loading and in 35 min with 1 g/L catalyst loading. Ag@TiO2 nanoparticles were found to be superior to TiO2 nanoparticles in photocatalytic disinfection of water. Kinetics of disinfection followed Chick’s law, and the pseudo-first-order rate constant was 0.0168 min?1 for a catalyst loading of 0.1 g/L. Disinfection of water and degradation of endotoxins (harmful disinfection residual) occurred simultaneously during photocatalysis thereby making the treated water safe for use. Endotoxin degradation showed a shifting order of kinetics. The rate of photocatalysis with nanoparticles immobilised in cellulose acetate film was marginally lower as compared to that of free nanoparticles. Negligible Ag ion leakage and re-growth of cells post-photo-catalytic treatment of water confirmed that complete disintegration of E. coli occurred during photocatalysis making the treated water safe for use. Therefore, Ag@TiO2 nanoparticles have a potential for large-scale application in drinking water treatment plants and household purification units. © 2016, Springer-Verlag Berlin Heidelberg.Item Photocatalytic water disinfection under solar irradiation by Ag@TiO2 core-shell structured nanoparticles(Elsevier Ltd, 2017) Sreeja, S.; Shetty K, V.K.The Ag core-TiO2 shell structured (Ag@TiO2) nanoparticles were found to be efficient in the disinfection of water under solar light irradiation both in free and immobilized form. Complete disinfection of 40 ? 108 CFU/mL Escherchia coli cells was achieved in 15 min by solar photocatalysis with 0.4 g/L Ag@TiO2 catalyst loading. Ag@TiO2 nanoparticles were found to be superior to TiO2 nanoparticles in solar disinfection. Photocatalysis rate was found to increase with increase in catalyst loading and with decrease in cell concentration. Ag@TiO2 nanoparticles showed their efficacy in the degradation of endotoxin, a harmful disinfection byproduct. Kinetics of solar disinfection with Ag@TiO2 nanoparticles followed Chick's law. The kinetics of endotoxin degradation followed zero order kinetics at high concentrations of endotoxin. However at lower concentrations, rate followed a nth order model with n = 6.99. A lower rate of photocatalytic disinfection with Ag@TiO2 nanoparticles immobilized on cellulose acetate as compared to that in their free form was observed, owing to diffusional and light penetration limitations. The re-growth of cells after photocatalytic disinfection was below the detectable limits, thus proving the potential of the process to produce safe drinking water. Ag@TiO2 nanoparticles can find potential application in solar water disinfection and the process which harnesses the solar energy may prove to be energy efficient and economical, thus can be easily adopted for large scale applications and portable drinking water treatment units for domestic applications. © 2017 Elsevier Ltd
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