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Now showing items 1 - 15 of 15

  • Fluorescent competitive aptasensor for detection of aflatoxin B-1

    Mukherjee, Monali   Bhatt, Praveena   Manonmani, H. K.  

    Aflatoxin B1 (AFB(1)) is one of the most commonly found mycotoxins in food commodities, particularly cereals, oilseeds, spices and tree nuts. In the past decade, aptamers have come into limelight and emerged as a new biosensing element replacing antibodies in various detection formats. Herein we report a faster, more sensitive, high throughput method for the detection of AFB(1) using AFB(1)-specific aptamers. The assay format was based on a competitive reaction of the fluorescent tagged aptamer specific to AFB(1) with the aflatoxin conjugate. Under optimal conditions, a linear range of detection (50 ng to 50 pg) was achieved with a limit of detection (LOD) of 10 pg/mL in the buffer system. Results of inter-and intra-assay revealed that the assay was repeatable with standard deviation in acceptable range. The assay was also validated in food samples such as dried red chilies, groundnut and whole pepper with recovery in the range of 92 to 102% at 10 ng/mL and 100 pg/mL levels. The aptasensor assay was also compared with standard analytical method of HPLC and was found to be more sensitive. This detection technique has the potential to be developed into a biosensor platform for AFB(1) detection.
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  • Fate and Degradation of POP-Hexachlorocyclohexane

    Bhatt, Praveena   Kumar, M. Suresh   Chakrabarti, Tapan  

    Hexachlorocyclohexane (HCH) and its isomers are one of the most frequently detected chlorinated contaminants in the environment. In spite of the ban on technical grade HCH and restricted use of -HCH (lindane), its residues have not stopped from entering the environment. Its extensive use in the past, present use of lindane in several countries, unused stockpiles of date-expired HCH from earlier manufacturing, as well as leachates from earlier disposal at dump sites continue to pollute the biosphere. Because HCH is a persistent organic pollution (POP) known to have several toxic and deleterious effects on human health and wildlife, it becomes imperative to remove this substance of serious concern to the global community. A better understanding on the fate and degradation of this POP in the environment will facilitate in drawing measures to mitigate this chemical and bring about bioremediation of already contaminated sites. This review focuses on the fate, contamination levels, abiotic and biotic degradation of HCH isomers, genes and enzymes involved in microbial degradation, and future research needs in this area.
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  • Biodegradation of Chlorinated Compounds—A Review

    Bhatt, Praveena   Kumar, M. Suresh   Mudliar, Sandeep   Chakrabarti, Tapan  

    The pressures of an ever-increasing population and industrial development have led to the addition of an array of man-made chemicals in the environment, leading to tremendous deterioration in environmental quality. Contamination of soil, air, water, and food is one of the major problems facing the industrialized world today. Significant regulatory steps have been taken to eliminate or to reduce production and/or release of these chemicals into the environment. A major class of these chemicals is chlorinated compounds, most of which are toxic and hazardous. Application of microbial processes to decontaminate environmental media polluted with these compounds will require a better understanding of why and how microorganisms can degrade them and utilize them for their own survival as well as clean the environment. This review focuses on different microbial processes for biodegradation of chlorinated compounds and enzymes involved therein that are responsible for their degradation.
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  • Fluorescent aptaswitch for chloramphenicol detection – Quantification enabled by immobilization of aptamer

    Sharma, Richa   Satyaprasad Akshath, Uchangi   Bhatt, Praveena   Raghavarao, KSMS  

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  • Chemical Composition and Nutraceutical Potential of Indian Borage (Plectranthus amboinicus) Stem Extract

    Bhatt, Praveena   Joseph, Gilbert Stanley   Negi, Pradeep Singh   Varadaraj, Mandyam Chakravarthy  

    The stem of Indian borage (Plectranthus amboinicus) was found to be an antioxidant rich fraction as evaluated by in vitro models such as DPPH free radical scavenging, reducing power assay, superoxide anion radical scavenging, and total antioxidant capacity. The extract also exhibited antiplatelet aggregation ability, antibacterial activity, and antiproliferative effect against cancer cell lines: Caco-2, HCT-15, and MCF-7. Phytochemical evaluation of the extract revealed the occurrence of total phenolics (49.91mg GAE/g extract), total flavonoids (26.6mg RE/g extract), and condensed tannins (0.7mg TAE/g extract). Among the major phenolics, rosmarinic acid (6.160mg/g extract) was predominant, followed by caffeic acid (0.770mg/g extract), rutin (0.324mg/g extract), gallic acid (0.260mg/g extract), quercetin (0.15mg/g extract), and p-coumaric acid (0.104mg/g extract). The appreciable biological activity and presence of biomolecules in the methanolic extract of stem indicate its potential application as functional food ingredients and nutraceuticals.
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  • Tunneling of redox enzymes to design nano-probes for monitoring NAD(+) dependent bio-catalytic activity

    Akshath, Uchangi Satyaprasad   Bhatt, Praveena  

    Monitoring of bio-catalytic events by using nano-probes is of immense interest due to unique optical properties of metal nanoparticles. In the present study, tunneling of enzyme activity was achieved using redox cofactors namely oxidized cytochrome-c (Cyt-c) and Co-enzyme-Q (Co-Q) immobilized on Quantum dots (QDs) which acted as a bio-probe for NAD(+) dependent dehydrogenase catalyzed reaction. We studied how electron transfer from substrate to non-native electron acceptors can differentially modify photoluminescence properties of CdTe QDs. Two probes were designed, QD-Ox-Cyt-c and QD-Ox-Co-Q which were found to quench the fluorescence of QDs. However, formaldehyde dehydrogenase (FDH) catalyzed reduction of Cyt-c and Co-Q on the surface of QDs lead to fluorescence turn-on of CdTe QDs. This phenomenon was successfully used for the detection of HCHO in the range of 0.01-100,000 ng/mL (LOD of 0.01 ng/mL) using both QD-Ox-Cyt-c (R-2=3D0.93) and QD-Ox-Co-Q (R-2=3D0.96). Further probe performance and stability in samples like milk, wine and fruit juice matrix were studied and we could detect HCHO in range of 0.001-100,000 ng/mL (LOD of 0.001 ng/mL) with good stability and sensitivity of probe in real samples (R-2=3D0.97). Appreciable recovery and detection sensitivity in the presence of metal ions suggests that the developed nano-probes can be used successfully for monitoring dehydrogenase based bio-catalytic events even in the absence of NAD(+). Proposed method is advantageous over classical methods as clean up/derivatization of samples is not required for formaldehyde detection. (C) 2016 Elsevier B.V. All rights reserved.
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  • Modeling of caffeine degradation kinetics during cultivation of Fusarium solani using sucrose as co-substrate

    Nanjundaiah, Shwetha   Mutturi, Sarma   Bhatt, Praveena  

    Microbial kinetics for simultaneous caffeine degradation and its biotransformation to theophylline has been investigated using Fusariurn solani. Caffeine was utilized by the fungus as a sole nitrogen source in the presence of sucrose, which served as the primary carbon source. A reaction mechanism involving Monod kinetics with both substrate and product inhibition was formulated based on experimental evidence. A total of thirteen kinetic parameters were involved in the model formulation and these were estimated using simulated annealing algorithm. Moreover, the parameter estimation was carried out for three different experimental sets simultaneously with varying initial sucrose concentration, in order to obtain a common set. Based on sensitivity analysis, among thirteen parameters, saturation constant of biomass accumulation from sucrose utilization (K-S1), yield of biomass from sucrose utilization (Y-X2/X1.,), lumped parameter which was defined as apparent yield of biomass from caffeine degradation process (Y-X2/X3), and yield of theophylline from caffeine metabolism (Y-X4/X3), were observed to be highly sensitive. The experimental results were in good agreement with the model predictions and have also been validated for an experimental setup which was not used for calibration. The results of the present study has potential application in the development of a process for detoxification of caffeine containing wastes as well as for production of a value added product theophylline. (C) 2017 Elsevier B.V. All rights reserved.
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  • Differential Interaction of Metal Ions with Gold Nanoclusters and Application in Detection of Cobalt and Cadmium

    Akshath, Uchangi Satyaprasad   Bhatt, Praveena   Singh, Sridevi Annapurna  

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  • Plectranthus amboinicus leaves stimulate growth of probiotic L-plantarum:Evidence for ethnobotanical use in diarrhea

    Shubha, J. R.   Bhatt, Praveena  

    Ethnopharmacological relevance: Leaves of Plectranthus amboinicus are consumed in India along with buttermilk (a probiotic source) during pathogen induced diarrhea. This treatment is known to reduce the number of episodes as well as duration of diarrhea. Aim of the study: In the background of its ethnobotanical use, the present investigation was carried out to determine whether, apart from having an antimicrobial activity on pathogens, the leaves could possibly also have a positive effect on the beneficial microflora of the gut resulting in accelerated microbial ecological balance. Materials and methods: The growth stimulating activity of the hot water extract (HWE) of P. amboinicus leaves on probiotic Lactobacillus plantarum was determined by microbroth dilution technique and viable plate count method in selective medium (MRS) as well as in fermented milk. The ability of the bacteria to utilize the phytoconstituents of HWE primarily phenolic acids and sugars was determined by assaying for phenolic acid decarboxylase by SDS-PAGE and beta-galactosidase activity by beta-gal ONPG assay. Results: HWE of P. amboinicus leaves inhibited growth of pathogens (Escherichia coli and Salmonella typhimurium) while stimulated the growth of L. plantarum. SDS-PAGE gel showed the presence of phenolic acid decarboxylase enzyme induced in the presence of HWE in L plantarum indicating the utilization of polyphenols by the bacteria. Cells grown on HWE also showed beta-galactosidase activity indicating their ability to utilize sugars present in HWE. Conclusion: Indian borage leaves have a prebiotic effect on the probiotic bacteria (L plantarum) which utilizes the phytoconstituents of the leaves by producing necessary metabolic enzymes. This work provides evidence in the traditional use of the leaves in the alleviation of diarrhea by accelerating microbial gut balance during infection. (c) 2015 Elsevier Ireland Ltd. All rights reserved.
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  • Aptamer as capture agent in enzyme-linked apta-sorbent assay (ELASA) for ultrasensitive detection of Aflatoxin B1.

    Mukherjee, Monali   Manonmani, H K   Bhatt, Praveena  

    Aflatoxin B1 (AFB1), is one of the most toxic mycotoxins found to contaminate various food commodities like cereals, dried fruits, tree nuts, spices and crude vegetable oils. In spite of considerable progress in analytical techniques, there is still a need to develop rapid and highly sensitive detection platforms for AFB1. In this study, AFB1 specific aptamer was used as a capture molecule to develop an enzyme-linked apta-sorbent assay (ELASA) for ultrasensitive detection of AFB1. Under optimized conditions, the assay had a linear detection range from 1=E2=80=AFmug to 1=E2=80=AFpg with a limit of detection (LOD) of 1=E2=80=AFpg/mL in buffer. Conventional ELISA with AFB1 hapten as the capture agent (LOD=E2=80=AF=3D=E2=80=AF10=E2=80=AFpg/mL) was also carried out to compare the results with the present method. Recovery studies in food samples like dried red chillies, groundnut and pepper using both the methods was found to be in the range of 88.49-106.4% at 10=E2=80=AFng/mL and 87.4% to 95.8% at 5=E2=80=AFng/mL for ELASA and 76.56-127.68% at 10=E2=80=AFng/mL and 82-101.2% at 5=E2=80=AFng/mL for ELISA. Higher detection (10 fold) and better recovery using ELASA suggest that the method could offer an early, ultrasensitive, high-throughput, qualitative and semi-quantitative detection of AFB1 in contaminated food samples. Copyright =C2=A9 2018 Elsevier Ltd. All rights reserved.
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  • Fluorescence Based Turn-on Probe for the Determination of Caffeine Using Europium-Tetracycline as Energy Transfer Complex

    Nanjundaiah, Shwetha   Krishna, Honnur   Bhatt, Praveena  

    The study describes a simple and sensitive fluorometric sensor based on the enhancement of fluorescence intensity of Europium ion (Eu3+) - tetracycline (TC) charge transfer complex on addition of caffeine. The Eu3+-TC ternary complex has a characteristic emission peak at 615 nm (lambda(ex) =3D 375 nm), the intensity of which increases with increase in concentration of caffeine. The caffeine sensor assay was found to be linear in the range of 0.0515 mM to 51.5 mM. The limit of detection and quantification were found to be 0.0515 mM and 0.382 mM, respectively. A caffeine recovery of 90 to 110 % in biological samples (serum and urine) indicated minimal interference by commonly present excipients in the samples. Rosenthal plots to calculate the binding capacity of caffeine with the Eu3+- TC complex revealed an association constant (K) of 238 x 10(3) L/mol and binding number (N) of 1.9. Bland-Altman plot comparing the developed assay and HPLC showed good agreement between values obtained by both the methods. The proposed fluorescent chemical sensor is a rapid and convenient method to determine caffeine with excellent recovery and low detection limit. The probable reaction mechanism for the formation of the turn on fluorescent probe enhancer is discussed.
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  • Antiaflatoxigenic and Antimicrobial Activities of Schiff Bases of 2-Hydroxy-4-methoxybenzaldehyde,Cinnamaldehyde,and Similar Aldehydes

    Harohally, Nanishankar V.   Cherita, Chris   Bhatt, Praveena   Appaiah, K. A. Anu  

    2-Hydroxy-4-methoxybenzaldehyde (HMBA) is a nontoxic phenolic flavor from dietary source Decalipus hamiltonii and Hemidesmus indicus. HMBA is an excellent antimicrobial agent with additional antiaflatoxigenic potency. On the other hand, cinnamaldehyde from cinnamon is a widely employed flavor with significant antiaflatoxigenic activity. We have attempted the enhancement of antiaflatoxigenic and antimicrobial properties of HMBA, cinnamaldehyde, and similar molecules via Schiff base formation accomplished from condensation reaction with amino sugar (D-glucamine). HMBA derived Schiff bases exhibited commendable antiaflatoxigenic activity at the concentration 0.1 mg/mL resulting in 9.6 +/- 1.9% growth of Aspergillus flavus and subsequent 91.4 +/- 3.9% reduction of aflatoxin B-1 with respect to control.
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  • Enhanced biodegradation of hexachlorocyclohexane in upflow anaerobic sludge blanket reactor using methanol as an electron donor

    Bhatt, Praveena   Kumar, M. Suresh   Mudliar, Sandeep   Chakrabarti, Tapan  

    Anaerobic dechlorination of technical grade hexachlorocyclohexane (THCH) was studied in a continuous upflow anaerobic sludge blanket (UASB) reactor with methanol as a supplementary substrate and electron donor. A reactor without methanol served as the experimental control. The inlet feed concentration of THCH in both the experimental and the control UASB reactor was 100 mg l(-1). After 60 days of continuous operation, the removal of THCH was >99% in the methanol-supplemented reactor as compared to 20-35% in the control reactor. THCH was completely dechlorinated in the methanol fed reactor at 48 h HRT after 2 months of continuous operation. This period was also accompanied by increase in biomass in the reactor, which was not observed in the experimental control. Batch studies using other supplementary substrates as well as electron donors namely acetate, butyrate, formate and ethanol showed lower % dechlorination (<8 5%) and dechlorination rates (<3 mg g(-1) d(-1)) as compared to methanol (98%, 5 mg g(-1) d(-1)). The optimum concentration of methanol required, for stable dechlorination of THCH (100 mg l(-1)) in the UASB reactor, was found to be 500 mg l(-1). Results indicate that addition of methanol as electron donor enhances dechlorinationof THCH at high inlet concentration, and is also required for stable UASB reactor performance. (C) 2007 Elsevier Ltd. All rights reserved.
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  • Gold nanoparticle synthesis coupled to fluorescence turn-on for sensitive detection of formaldehyde using formaldehyde dehydrogenase

    Akshath, Uchangi Satyaprasad   Bhatt, Praveena  

    Ultrasensitive detection of toxins by nanoparticle-fluorophore interaction has been studied extensively in the past decade. The present study highlights the detection of formaldehyde based on fluorescence turn-on induced by NADH mediated GNP synthesis. The growth solution consisted of CTAB, Au3+ and fluorescein dye. Extensive fluorescence quenching was observed upon interaction of fluorescein with the growth solution. However, addition of NADH led to dose dependent fluorescence turn-on. This behavior was successfully employed for the ultrasensitive detection of formaldehyde (0.01 pg to 300 pg mL(-1) with R-2 =3D 0.9439) as a function of NADH using formaldehyde dehydrogenase enzyme. Metal ion interactions with the proposed system were also studied. We propose that the initial fluorescence quenching is due to CTAB-fluorescein-Au3+ interaction. Addition of NADH to the growth solution led to initiation of gold nanoparticle synthesis by the reduction of Au3+ to Au-0 that induced more polarity on the CTAB micellar surface causing fluorescein-CTAB transition and turn-on fluorescence, further leading to the detection of NADH. Also, at increased NADH/formaldehyde concentration, a fluorescence decrease was observed which is due to the efficient synthesis of gold nanoparticles leading to spectral overlap. The proposed method of Au3+ reduction coupled to fluorescence turn-on can be applied for monitoring NADH dependent dehydrogenase reactions at ultrasensitive levels.
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  • Assessment of bioremediation possibilities of technical grade hexachlorocyclohexane (tech-HCH) contaminated soils

    Bhatt, Praveena   Chakrabarti, Tapan  

    Hexachlorocyclohexane (HCH) is a broad spectrum insecticide still used in some of the developing countries, though developed countries have banned or curtailed its use. Even in those countries where the use of t-HCH has been discontinued for a number of years, the problem of residues of all isomers of t-HCH remains because of its high persistence. These insecticides in the soil disturb the delicate equilibrium between microorganisms and their environment. Few reports on the degradation of t-HCH isomers in soil are present in literature, and very little information is available on the effect of these t-HCH isomers on soil microflora. In the present study, an attempt has been made to see the microbial diversity in the uncontaminated soils and the effect of application of t-HCH on the soil microflora. The soil was spiked with t-HCH and incubated, at regular time intervals the soil samples were analyzed for microbial diversity as well as t-HCH isomers residues. The results show that at higher concentrations of t-HCH, microbial populations were inhibited and the inhibited populations did not reappear even after prolonged incubation. Potential t-HCH degrading cultures were isolated and subjected to further acclimation in order to enhance their degradation capacity. The results are presented and discussed in this paper. (C) 2006 Elsevier B.V. All rights reserved.
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