Faculty Publications
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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 Modelling and simulation of steady-state phenol degradation in a pulsed plate bioreactor with immobilised cells of Nocardia hydrocarbonoxydans(2011) Shetty K, V.S.; Verma, D.K.; Srinikethan, G.A novel bioreactor called pulsed plate bioreactor (PPBR) with cell immobilised glass particles in the interplate spaces was used for continuous aerobic biodegradation of phenol present in wastewater. A mathematical model consisting of mass balance equations and accounting for simultaneous external film mass transfer, internal diffusion and reaction is presented to describe the steady-state degradation of phenol by Nocardia hydrocarbonoxydans (Nch.) in this bioreactor. The growth of Nch. on phenol was found to follow Haldane substrate inhibition model. The biokinetic parameters at a temperature of 30 ± 1 °C and pH at 7.0 ± 0.1 are ? m = 0.5397 h -1, K S = 6.445 mg/L and K I = 855.7 mg/L. The mathematical model was able to predict the reactor performance, with a maximum error of 2% between the predicted and experimental percentage degradations of phenol. The biofilm internal diffusion rate was found to be the slowest step in biodegradation of phenol in a PPBR. © 2010 Springer-Verlag.Item Shear stress effects on production of exopolymeric substances and biofilm characteristics during phenol biodegradation by immobilized Pseudomonas desmolyticum (NCIM2112) cells in a pulsed plate bioreactor(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2016) Veena, B.R.; Shetty K, K.V.; Saidutta, M.B.This article reports studies on a continuous pulsed plate bioreactor (PPBR) with the cells of Pseudomonas desmolyticum (NCIM2112) immobilized on granular activated carbon (GAC) used as a biofilm reactor for biodegradation of phenol. Almost complete removal of 200 ppm phenol could be achieved in this bioreactor. Biofilm structure and characteristics are influenced by hydrodynamic and shear conditions in bioreactors. In this article, the effect of shear stress induced by frequency of pulsation on biofilm characteristics during the startup period in the PPBR is reported. The startup time decreased with the increase in frequency of pulsation. The formation of biofilm in PPBR was found to have three phases: accumulation, compaction, and plateau. The effect of frequency on production of exoploymeric substances (EPS) such as, protein, carbohydrate, and humic substance is reported. An increase in shear stress induced by the frequency of pulsation increased the production of exopolymeric substances in the biofilm during startup of the bioreactor. Increase in shear stress caused a decrease in biofilm thickness and an increase in dry density of the biofilm. Increase in shear stress resulted in a smoother and thinner biofilm surface with more compact and dense structure. © 2016, Copyright © Taylor & Francis Group, LLC.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 The combined effects of carbon/nitrogen ratio, suspended biomass, hydraulic retention time and dissolved oxygen on nutrient removal in a laboratory-scale anaerobic–anoxic–oxic activated sludge biofilm reactor(IWA Publishing, 2018) Manu, D.S.; Thalla, A.K.The current trend in sustainable development deals mainly with environmental management. There is a need for economically affordable, advanced treatment methods for the proper treatment and management of domestic wastewater containing excess nutrients (such as nitrogen and phosphorus) which can cause eutrophication. The reduction of the excess nutrient content of wastewater by appropriate technology is of much concern to the environmentalist. In the current study, a novel integrated anaerobic–anoxic–oxic activated sludge biofilm (A2O-AS-biofilm) reactor was designed and operated to improve the biological nutrient removal by varying reactor operating conditions such as carbon to nitrogen (C/N) ratio, suspended biomass, hydraulic retention time (HRT) and dissolved oxygen (DO). Based on various trials, it was seen that the A2O-AS-biofilm reactor achieved good removal efficiencies with regard to chemical oxygen demand (95.5%), total phosphorus (93.1%), ammonia nitrogen concentration (NH4þ-N) (98%) and total nitrogen (80%) when the reactor was maintained at C/N ratio of 4, suspended biomass of 3 to 3.5 g/L, HRT of 10 h, and DO of 1.5 to 2.5 mg/L. Scanning electron microscopy (SEM) of suspended and attached biofilm showed a dense structure of coccus and bacillus bacteria with the diameter ranging from 0.3 to 1.2 ?m. The Fourier transform infrared (FTIR) spectroscopy results indicated phosphorylated macromolecules and carbohydrates mix or bind with extracellular proteins in exopolysaccharides. © IWA Publishing 2018.Item Influence of various operating conditions on wastewater treatment in an AS-biofilm reactor and post-treatment using TiO2-based solar/UV photocatalysis(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2019) Manu, D.S.; Thalla, A.K.In the present study, the effect of carbon to nitrogen (C/N) ratio, suspended biomass concentration (X), hydraulic retention time (HRT) and dissolved oxygen (DO) on chemical oxygen demand (COD) and nutrient removal from wastewater was investigated in a lab-scale activated sludge (AS)-biofilm reactor. Furthermore, in order to improve the quality of the treated wastewater, photocatalysis by TiO2 was investigated as a post-treatment technology, using solar and UV irradiations. The AS-biofilm reactor provided a substantial removal efficiency in terms of COD, ammonia nitrogen (NH+4-N), total nitrogen (TN) and total phosphorous when the system was maintained at C/N ratio 6.66, X in the range 2–2.5 g/L, HRT 10 h, DO in the range of 3.5–4.5 mg/L and organic loading rate (OLR) of 0.96 kg COD/m3d during Run 1. Similarly, when the reactor was maintained at C/N ratio 10, X in the range of 3–3.5 g/L, HRT 8 h, DO in the range of 3.5–4.5 mg/L and OLR of 1.8 kg COD/m3d during Run 2. The microstructure of suspended and attached biomass comprised a dense bacterial structure of cocci and bacillus microorganisms. The UV photocatalysis was found to be better than solar photocatalysis during the comparative analysis. The maximum removal efficiencies of COD, most probable number and phosphorous at optimum conditions in the case of UV and solar irradiations were 72%, 95%, 52% and 71%, 99%, 50%, respectively. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.Item Evaluation of the surface characteristics and antibacterial properties of Titanium dioxide nanotube and methacryloyloxyethylphosphorylcholine (MPC) coated orthodontic brackets-a comparative invitro study(Springer Science and Business Media Deutschland GmbH, 2024) Rao, M.; Ashith, M.V.; Suman, E.; Isloor, A.M.; Shetty, N.J.; Srikant, S.Objectives: White spot lesions are the most common iatrogenic effect observed during orthodontic treatment. This study aimed to compare the surface characteristics and antibacterial action of uncoated and coated orthodontic brackets. Materials and methods: Sixty commercially available stainless steel brackets were coated with TiO2 nanotubes and methacryloyloxyethylphosphorylcholine. The sample was divided into Group 1: uncoated orthodontic brackets, Group 2: Stainless steel brackets with TiO2 nanotubes coating, Group 3: Stainless steel brackets with methacryloyloxyethylphosphorylcholine coating, and Group 4: Stainless steel brackets with TiO2 nanotubes combined with methacryloyloxyethylphosphorylcholine coating. Surface characterization was assessed using atomic force microscopy and scanning electron microscopy. Streptococcus mutans was selected to test the antibacterial ability of the orthodontic brackets, total bacterial adhesion and bacterial viability were assessed. The brackets were subjected to scanning electron microscopy to detect the presence of biofilm. Results: The surface roughness was the greatest in Group 1 and least in Group 2 followed by Group 4 and Group 3 coated brackets. The optical density values were highest in Group 1 and lowest in Group 4. Comparison of colony counts revealed high counts in Group 1 and low counts in Group 4. A positive correlation between surface roughness and colony counts was obtained, however, was not statistically significant. Conclusions: The coated orthodontic brackets exhibited less surface roughness than the uncoated orthodontic brackets. Group 4 coated orthodontic brackets showed the best antibacterial properties. Clinical relevance: Coated orthodontic brackets prevent adhesion of streptococcus mutans and reduces plaque accumulation around the brackets thereby preventing formation of white spot lesions during orthodontic treatment. © The Author(s) 2024.Item Non-reactive biochar and Bacillus pumilus RSB17-based healing powder: A sustainable solution for enhanced bacterial viability in self-healing mortar(Elsevier B.V., 2025) Anoop, P.P.; Palanisamy, T.Existing mortar uses self-healing powders that are based on mineral admixtures, whose reactive nature negatively impacts bacterial viability and diminishes their effectiveness over time. This study aims to develop non-reactive, sustainable biochar-based healing powders with extended bacterial viability to serve as self-healing admixture in bio-mortar. Biochar from coconut husk, coconut shell, and coconut leaf petiole was evaluated for compatibility with Bacillus pumilus RSB17, emphasizing bacterial growth and calcium carbonate precipitation. Coconut shell biochar demonstrated superior performance and was used to formulate a microbial biochar healing powder. Another healing powder was prepared by lyophilizing the bacterial spore solution without protectants. The shelf life was evaluated for 180 days at 4 °C and 25 °C, demonstrating that microbial biochar healing powder at 4 °C maintained bacterial viability above the 4.5 log CFU/g threshold necessary for effective calcium carbonate precipitation, while lyophilized spore powder stored at 25 °C dropped below the threshold at 90 days. Microbial biochar healing powder stored at 4 °C for 180 days was integrated into the mortar, which healed crack width up to 0.80 mm at 56 days under submerged rainwater maintained at 27 °C ± 2 °C and 85 % ± 5 % relative humidity. Electrical resistivity decreased from 28.16 ?·m to 21.35 ?·m, the permeability coefficient dropped from 153.90 mm/s to 0 mm/s, and compressive strength regained 90.53 %, which collectively indicated enhanced self-healing. Microstructural analysis confirmed the stable cuboid calcite crystals with a crystallite size of 86.62 nm. Thus, Microbial biochar healing powder produced from coconut shell biochar and Bacillus pumilus RSB17 and stored at 4 °C is an effective self-healing admixture for bio-mortar applications with a minimum storage period of 180 days. © 2025 Elsevier B.V.Item Amyloid-like Protein-Metal Sulfide Nanocoatings for Synergistic Photothermal and Antibacterial Implant Surface Protection(American Chemical Society, 2025) Li, K.; Zhang, X.; Xu, L.; Xu, K.; Rao, X.; Murugesan, S.; Barão, V.A.R.; Yang, P.; Kang, E.-T.Preventing bacterial adhesion and biofilm formation is essential for the long-term success of biomedical implants. Implant-associated infections remain a significant clinical challenge, underscoring the urgent need for effective and durable antimicrobial surface strategies. This study develops a nanocoating with dual antibacterial adhesion and photothermal antibacterial properties for biomedical surface modification. Bovine serum albumin-templated metal sulfide (MS@BSA) nanocomposites are synthesized and converted into a stable nanofilm via phase-transitioned BSA (PTB) self-assembly. The MS@PTB coating adheres to various substrates and demonstrates broad-spectrum antibacterial activity. In vitro assays show that the copper sulfide@PTB (CuS@PTB) coating significantly reduces bacterial attachment and suppresses biofilm development upon 808 nm near-infrared irradiation. RNA sequencing identifies differentially expressed genes in common pathogens, indicating disrupted respiration, energy metabolism, and virulence pathways as well as stress responses to heat and copper ions. In vivo experiments using rat subcutaneous infection and abdominal wall defect models demonstrate that CuS@PTB markedly reduces bacterial load and inflammatory responses while accelerating tissue regeneration and maintaining excellent biocompatibility. The results demonstrate the synergistic antibacterial effects of photothermal heating and Cu ion release, supporting CuS@PTB as a promising antimicrobial surface coating for implantable biomaterials. © 2025 American Chemical Society