Showing papers by "Sathyanarayana N. Gummadi published in 2020"
TL;DR: In this article, the antibacterial, antioxidant and cytotoxicity behavior of silver ferrite nanoparticles (AgFeO2 NPs) synthesized through chemical and green routes were compared.
29 citations
TL;DR: In this paper, the effect of different operating conditions such as initial pH (4, 7 and 9), AgFeO2 NPs loading (10, 20, 50, and 100) mg/L, and caffeine concentration (20, 50 and 100 ppm) on degradation efficiency was studied.
Abstract: Caffeine is a persistent chemical with toxic effects on various biological systems in the environment which initiates the necessity to degrade the caffeine. This study aimed to degrade caffeine using Amaranthus blitum leaf extract mediated silverferrite nanoparticles (AgFeO2-NPs) under compact fluorescent lamp illumination in shake flask by photocatalysis. The AgFeO2 NPs were monodispersed with spherical shape (92 nm in average size and bandgap of 1.9 eV), holds higher photocurrents and surface area of 10.4 μA/cm2 and 145.21 m2/g respectively. The effect of different operating conditions such as initial pH (4, 7and 9), AgFeO2 NPs loading (10, 20, 50, and 100) mg/L, and caffeine concentration (10, 20, 50 and 100) ppm was studied on degradation efficiency. The results showed that optimal conditions led to maximum degradation of 99.9% at pH 9.0, 50 mg/L NPs dose with initial caffeine concentration of 50 ppm in 15 h compared to photolysis and NPs under dark condition. Under optimized conditions, (∼ 120 ppm caffeine in synthetic wastewater, pH 9.3, and 50 mg/L of AgFeO2 NPs), it was found that 95% degradation occurred in 24 h. Also, AgFeO2 NPs found to degrade polyphenols under light conditions suggesting a potential catalyst for treating caffeine wastewater.
15 citations
TL;DR: Predicted specific substrate utilization and product excretion rates have been correlated well with the experimental observations, which validate the proposed metabolic pathway developed from metabolic footprinting data.
8 citations
TL;DR: It is reported that Ca-Est is hormone-sensitive lipase with novel GYSMG pentapeptide motif at a catalytic domain with high preference for p-nitrophenyl butyrate.
Abstract: Gene CA_C0816 codes for a serine hydrolase protein from Clostridium acetobutylicum (ATCC 824) a member of hormone-sensitive lipase of lipolytic family IV. This gene was overexpressed in E. coli strain BL21and purified using Ni2+–NTA affinity chromatography. Size exclusion chromatography revealed that the protein is a dimer in solution. Optimum pH and temperature for recombinant Clostridium acetobutylicum esterase (Ca-Est) were found to be 7.0 and 60 °C, respectively. This enzyme exhibited high preference for p-nitrophenyl butyrate. KM and kcat/KM of the enzyme were 24.90 µM and 25.13 s−1 µM−1, respectively. Sequence analysis of Ca-Est predicts the presence of catalytic amino acids Ser 89, His 224, and Glu 196, presence of novel GYSMG conserved sequence (instead of GDSAG and GTSAG motif), and undescribed variation of HGSG motif. Site-directed mutagenesis confirmed that Ser 89 and His 224 play a major role in catalysis. This study reports that Ca-Est is hormone-sensitive lipase with novel GYSMG pentapeptide motif at a catalytic domain.
8 citations
TL;DR: In this paper, a black-oil biochemical multispecies reactive transport model was developed by coupling the kinetic model with the corresponding transport model involving microbial sorption, and the results showed that at very low reservoir porosity, an early breakthrough of nutrients, microbes, and biosurfactant leave insignificant concentrations in their respective fronts, which are insufficient for the recovery of the trapped oil.
Abstract: During the implementation of a microbial-enhanced-oil-recovery (EOR) (MEOR) technique in a sandstone formation, various reservoir physicochemical, microbial kinetic, and operational parameters play major roles in governing the efficiency of crude-oil recovery from a hydrocarbon reservoir. The present study numerically investigates the sensitivity of sandstone formation effective porosity; different injected strains of the species Bacillus under optimal metabolic conditions and possessing distinct values of maximum microbialspecific-growth rate, Monod saturation constant, and yield coefficient; and crucial operational parameters on biomass and biosurfactant production and their effects on microscopic oil-displacement efficiency within the sandstone reservoir, along with prompting modifications in rock physicochemical properties. A black-oil biochemical multispecies reactive transport model in porous sandstone media is developed by coupling the kinetic model with the corresponding transport model involving microbial sorption. The governing equations involve coupled transport of nutrients and microbes by dispersion and convection, growth and decay rates of microbes, chemotaxis, nutrient consumption, and deposition of microbes and nutrients on rock-grain surfaces caused by reversible/irreversible sorption. Coupled empirical equations are used to estimate biosurfactant production, oil/water-interfacial-tension (IFT) reduction, change in the viscosity of injection fluid, and their effects on oil relative permeability and mobility, and thus a decrease in residual oil saturation within the reservoir. The finitedifference-discretization technique is adopted to solve the governing equations. Results of the present model are found to be numerically stable and match very well, when verified, with the previously published analytical, numerical, and experimental results. The model results suggest that at very low reservoir porosity (approximately 10%), an early breakthrough of nutrients, microbes, and biosurfactant leave insignificant concentrations in their respective fronts, which are insufficient for the recovery of the trapped oil. Also, increase in porosity to approximately 30% and beyond causes loss of nutrients, microbes, and biosurfactant because they undergo higher dispersion during their transport within the reservoir. Thus, sandstone formations possessing an intermediate effective porosity value of approximately 20% significantly enhance the efficiency of the overall MEOR process. Further, it is observed that the nature of microbes and nutrients used for MEOR application affect biosurfactant production, and in turn oil recovery, to a large extent. Those microbial species with far lower Monod-saturation-constant values have high affinity toward their substrates. This phenomenon dramatically increases the rates of nutrient consumption and production of biomass and biosurfactant within a reservoir when suitable substrate compounds are used, irrespective of differences in the yield coefficients of the microbes. Further MEOR simulation studies within a sandstone core exhibited maximum oil displacement and recovery at a run time of 5 hours, injected-microbial concentration of 4.32 10 mg/cm, and maximum specific growth rate of 0.35 hours. Bioplugging-induced formation damage negatively affecting the oil-recovery efficiency is also observed with an increase in the process run time. The screened microbe also exhibited the possibility of wettability alteration of sandstone-formation rock from mixed/oil-wet to water-wet. Thus, the present study provides an improved understanding of the combined effects of reservoir porosity, microbial kinetic, and key operational parameters on fundamental MEOR processes, which will better characterize and develop an effective strategy to determine the suitability of an MEOR technique in a typical sandstone reservoir. Moreover, the developed numerical model is easier to implement and produces faster results with relatively lower computational cost, which helps in making a quick decision before applying MEOR processes in the field.
7 citations
TL;DR: In this paper, improved mathematical and numerical models are developed in order to simulate the influence of important reservoir (effective porosity and longitudinal dispersivity), fluid and microbial kinetic (Monod half-saturation constant, substrate to biomass yield coefficient and substrate inhibition) parameters on dynamics of in-Situ microbial enhanced oil recovery (MEOR) processes using Bacillus sp. in a typical sandstone reservoir.
6 citations
TL;DR: This is the first biochemical evidence for heavy metals binding to the mitochondrial membrane protein leading to bidirectional translocation of PLs specifically towards phosphatidylethanolamine.
Abstract: Human phospholipid scramblases are a family of four homologous transmembrane proteins (hPLSCR1-4) mediating phospholipids (PLs) translocation in plasma membrane upon Ca2+ activation. hPLSCR3, the only homologue localized to mitochondria, plays a vital role in mitochondrial structure, function, maintenance, and apoptosis. Upon Ca2+ activation, hPLSCR3 mediates PL translocation at the mitochondrial membrane enhancing t-bid-induced cytochrome c release and apoptosis. Mitochondria are important target organelles for heavy-metals-induced apoptotic signaling cascade and are the central executioner of apoptosis to trigger. Pb2+ and Hg2+ toxicity mediates apoptosis by increased reactive oxygen species (ROS) and cytochrome c release from mitochondria. To discover the role of hPLSCR3 in heavy metal toxicity, hPLSCR3 was overexpressed as a recombinant protein in Escherichia coli Rosetta (DE3) and purified by affinity chromatography. The biochemical assay using synthetic proteoliposomes demonstrated that hPLSCR3 translocated aminophospholipids in the presence of micromolar concentrations of Pb2+ and Hg2+. A point mutation in the Ca2+-binding motif (F258V) led to a ∼60% loss in the functional activity and decreased binding affinities for Pb2+ and Hg2+ implying that the divalent heavy metal ions bind to the Ca2+-binding motif. This was further affirmed by the characteristic spectra observed with stains-all dye. The conformational changes upon heavy metal binding were monitored by circular dichroism, intrinsic tryptophan fluorescence, and light-scattering studies. Our results revealed that Pb2+ and Hg2+ bind to hPLSCR3 with higher affinity than Ca2+ thus mediating scramblase activity. To summarize, this is the first biochemical evidence for heavy metals binding to the mitochondrial membrane protein leading to bidirectional translocation of PLs specifically toward phosphatidylethanolamine.
6 citations
TL;DR: Murraya koenigii leaf extract mediated cysteine-functionalized magnetite nanoparticles (Cys-FeO NPs) were synthesized by the precipitation method and the successful binding of XR on functionalized NPs was confirmed through functional and structural studies.
5 citations
01 Jan 2020
TL;DR: In this paper, controlled experiments were carried out to study PM concentrations generated while performing different cooking methods including boiling (rice, urad dal and preparation of tea) and pan-frying (wheat roti and omlette).
Abstract: Indoor air pollution (IAP) predominantly contributed from biomass burning in rural households is a major health hazard. Cooking activities are significant sources of indoor particulate matter (PM). The present study focuses on characterising PM emissions from different cooking methods that are primarily prepared in rural areas of South India, in a simulated kitchen relying on biomass as fuel and estimation of respiratory dosage. Controlled experiments were carried out to study PM concentrations generated while performing different cooking methods including boiling (rice, urad dal and preparation of tea) and pan-frying (wheat roti and omlette). Multiple Particle Path Dosimetry (MPPD) was used to estimate deposition fractions in head, tracheobronchial and pulmonary regions of the human respiratory tract (HRT) for women. Further, PM dosage was assessed by entering the captured PM measurements and evaluated amongst different cooking methods. PM concentrations from pan-frying were ~1.6 times greater than boiling, primarily due to usage of oil for frying. Furthermore, pan-frying displayed higher dosage (412–2240 µg) compared to the boiling (258–1119 µg). However, urad dal displayed extreme amplification of 8.7 times than preparation of tea due to longer cooking duration. It is evident from above results that cooking methods are major attributes impacting IAP in rural areas with severe health impacts.
3 citations
TL;DR: Higher DO in the medium is required for efficient conversion of caffeine to theobromine which is in agreement that the reaction is oxidative demethylation which will be useful in shaking flask studies and scaling up processes.
Abstract: Caffeine is a plant alkaloid present in the large ratio over other emerging pollutants and it causes serious health effects on overdosage. Microbial degradation of caffeine produces metabolites tha...
3 citations
TL;DR: N-lauryl sarcosine (NLS) has been established as an effective detergent to extract the functionally active recombinant 6X-his- hPLSCR3 from the inclusion bodies and established the potency of polystyrene-based beads as a convenient, efficient, and alternate tool to dialysis in detergent removal.
Abstract: Membrane protein purification is a laborious, expensive, and protracted process involving detergents for its extraction. Purifying functionally active form of membrane protein in sufficient quantity is a major bottleneck in establishing its structure and understanding the functional mechanism. Although overexpression of the membrane proteins has been achieved by recombinant DNA technology, a majority of the protein remains insoluble as inclusion bodies, which is extracted by detergents. Detergent removal is essential for retaining protein structure, function, and subsequent purification techniques. In this study, we have proposed a new approach for detergent removal from the solubilized extract of a recombinant membrane protein: human phospholipid scramblase 3 (hPLSCR3). N-lauryl sarcosine (NLS) has been established as an effective detergent to extract the functionally active recombinant 6X-his- hPLSCR3 from the inclusion bodies. NLS removal before affinity-based purification is essential as the detergent interferes with the matrix binding. Detergent removal by adsorption onto hydrophobic polystyrene beads has been methodically studied and established that the current approach was 10 times faster than the conventional dialysis method. The study established the potency of polystyrene-based beads as a convenient, efficient, and alternate tool to dialysis in detergent removal without significantly altering the structure and function of the membrane protein.
TL;DR: This is the first report showing that this scramblase from Caenorhabditis elegans possesses a Ca2+-dependent and head group-independent scrambleblase activity.
Abstract: In this study, the SCRM-1 gene from Caenorhabditis elegans was cloned and overexpressed in E. coli to study the biochemical properties of scramblase. This is the first report showing that this scramblase from C. elegans possesses a Ca2+-dependent and head group-independent scramblase activity. The SCRM-1 of C.elegans possesses functional domains including a single EF-hand-like Ca2+ binding domain, as human scramblases do. A point mutation in the EF-hand-like Ca2+ binding motif results in loss of scramblase activity. Other biochemical assays like carbocyanine staining, Tb3+ luminescence, Tryptophan fluorescence, and CD spectroscopy strongly proved the role of the EF-hand motif for functional activity. The increase in protein size in solution upon incubating with Ca2+ shows ligand-dependent oligomerization and conformational changes.
TL;DR: It was found that alteration in both secondary and tertiary structures caused enzyme deactivation in acidic pH while increased deactivation rates at alkaline pH was attributed to the variation of tertiary structure over time.
Abstract: The stability of Debaryomyces nepalensis NCYC 3413 xylose reductase, a homodimeric enzyme recombinantly expressed and purified from E. coli Rosetta cells, was studied at different pH ranging from 5.0 to 10.0. Deactivation kinetics at different pH were studied by analyzing residual activity of the recombinant enzyme over time at 40 °C whereas conformational changes and stability dependence were investigated by using circular dichroism and differential scanning calorimetry. Four osmolytes viz. glycerol, sucrose, trehalose and sorbitol were explored for their effect on the deactivation and melting temperatures of the enzyme under neutral and extreme pH conditions. The enzyme was found to be catalytically and structurally stable at pH 7.0 with half-life of 250 min and a melting temperature of 50 °C. It was found that alteration in both secondary and tertiary structures caused enzyme deactivation in acidic pH while increased deactivation rates at alkaline pH was attributed to the variation of tertiary structure over time. Estimated thermodynamic parameters also showed that the enzyme stability was highest at neutral pH with ΔH of 348 kcal/mole and ΔG40 of 9.53 kcal/mole. All four osmolytes were effective in enhancing enzyme stability by several folds at extreme pH with sorbitol being the most efficient, which increased enzyme half-life by 11-fold at pH 10.0 and 8-fold at pH 5.0.
01 Dec 2020
TL;DR: In this article, a black-oil biochemical multi-species reactive transport model in porous media is developed by coupling the kinetic model with the corresponding transport model, which involves coupled transport of nutrients and microbes by dispersion and convection, growth and decay rates of microbes, chemotaxis, nutrient consumption, and deposition of microbes and nutrients on rockgrain surfaces.
Abstract: During the implementation of microbial enhanced oil recovery (MEOR) technique in reservoirs, various reservoir and microbial kinetic parameters play major roles in governing the efficiency of crude oil recovery from hydrocarbon reservoirs. The present study numerically investigates the sensitivity of reservoir porosity, injected microbial species at different temperatures, maximum microbial specific growth rate, Monod saturation constant and yield coefficient on biomass and biosurfactant production and their impacts on microscopic oil displacement efficiency within the reservoir. A black-oil biochemical multi-species reactive transport model in porous media is developed by coupling the kinetic model with the corresponding transport model. The governing equations involve coupled transport of nutrients and microbes by dispersion and convection, growth and decay rates of microbes, chemotaxis, nutrient consumption, and deposition of microbes and nutrients on rock-grain surfaces. Coupled empirical equations are used to estimate biosurfactant production, oil-water interfacial tension reduction, change in viscosity of injection fluid and their impacts on oil mobility and decrease in residual oil saturation within reservoir. Finite difference discretization technique is adopted to solve the governing equations. Results of the present model are found to be numerically stable and match very well, when verified, with the previously published analytical and experimental results. The model results suggest that at very low reservoir porosity (less than 20%), an early breakthrough of nutrients, microbe and biosurfactant leave insignificant concentrations in their respective fronts which are insufficient for the recovery of the trapped oil. Also, increase in porosity beyond 20% causes loss of nutrients, microbes and biosurfactant because they undergo higher dispersion during their transport within reservoir. Further it is observed that the nature of microbes and nutrients used for MEOR application affect biosurfactant production and in turn oil recovery to a large extent. Those microbial species having very less Monod saturation constant values have high affinity towards their substrates. This phenomenon drastically increases the rates of nutrient consumption and production of biomass and biosurfactant within reservoir when suitable substrate compounds are used, irrespective of differences in the yield coefficients of the microbes. The optimized reservoir and microbial kinetic properties increase capillary number above 10−3 which further increases oil mobility towards production well and there is a significant decline in the effective residual oil saturation (less than 5%) within the reservoir. The present study provides an improved understanding of the combined effects of reservoir porosity and microbial kinetic parameters on fundamental MEOR processes which will better characterize the suitability of a MEOR technique in a typical petroleum reservoir. Moreover, the developed numerical model is easier to implement and produces faster results with relatively lower computational cost which helps in making quick decision before applying MEOR processes in the field.