Browsing by Author "R.K. Asthana"

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A comparison of proline, thiol levels and GAPDH activity in cyanobacteria of different origins facing temperature-stress
(2005) A.P. Singh; R.K. Asthana; Arvind M. Kayastha; S.P. Singh
Three cyanobacterial strains originating from different habitats were subjected to temperature shift exposures and monitored for levels of proline, thiol and activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Thermophile Mastigocladus laminosus (growth optimum, 40°C), raised the proline level 4.2-fold at low temperature (20deg;C), for the psychrophile Nostoc 593 (growth optimum, 20°C), it was raised 8-fold at 40°C while in the mesophile Nostoc muscorum (growth optimum, 30°C), the imino acid level increased 2.3-fold during temperature 'shiftdown' to 20°C or 3.5-fold in sets facing 'shiftup' (40°C). Alterations in thiol levels in the above strains were in line with proline. It is suggested that such fluctuations reflect metabolic shifts as a response to stress. Interestingly, GAPDH activity was maximum at the respective growth temperature optimum of M. laminosus (122 nmol NADPH oxidized min-1 mg-1 protein) and Nostoc 593 (141 nmol NADPH oxidized min-1 mg-1 protein) while in N. muscorum, it increased at 40°C (101 nmol NADPH oxidized min-1 mg-1 protein) and to 93.3 nmol NADPH oxidized min-1 mg-1 protein (20°C) relative to 86 nmol NADPH oxidized min -1 mg-1 protein at 30°C. It seems that extremophiles maintain the GAPDH activity/level during growth at their respective temperatures optimal while the mesophile increases it in order to cope up with temperature-stress.
A Study on Mixotrophic Approach for Maximizing Lipid Production in a Hypersaline Microalga, Dunaliella salina
(Springer, 2023) Abhishek Mohanta; Sk Riyazat Khadim; Prabhakar Singh; Laxmi; R.K. Asthana
The microalga, Dunaliella salina, is a treasure of fine chemicals, carotenoids, and lipids of industrial importance. The present investigation focused on the maximization of lipid content in the context of biofuel. Mixotrophic cultures growing in different combinations of sodium bicarbonate (NaHCO3) and glucose (Glu) or sodium acetate (Na-Ace) were monitored for essential growth parameters such as photosynthesis, dry biomass, and Chl a content. The maximum photosynthetic quantum yield (Fv/Fm) of all the screened mixotrophic cultures along with control ranged between 0.63 and 0.72, indicating the cells were in a good physiological state. The highest biomass productivity (33.46 ± 0.58 mg/L/d) was recorded in 1.0 mM NaHCO3 + 1.0 mM Glu-containing cultures. However, the highest lipid content (56% DCW) was recorded in 1.0 mM NaHCO3 + 0.5 mM Na-Ace-containing cultures. Interestingly, a 1.7-fold higher starch content (72.3 μg/mL) was recorded in 0.25 mM NaHCO3 + 0.5 mM Na-Ace over 1.0 mM NaHCO3 + 0.5 mM Na-Ace-containing cultures. Thus, data indicated that the higher concentration of NaHCO3 along with Na-Ace favoured lipid biosynthesis, while the lower concentration of NaHCO3 with Na-Ace favoured starch synthesis. Thus, substrate provision determined the desired products. Lipids obtained from D. salina at stage II (nitrogen-deficient condition) possessed ideal fuel properties according to international standards of EN 14214 and ASTM D6751. Therefore, the present work explored the threshold level of bicarbonate along with Na-Ace which was able to maintain good physiological status and produced higher lipids with better biodiesel properties. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Antimicrobial assay and genetic screening of selected freshwater Cyanobacteria and identification of a biomolecule dihydro-2H-pyran-2-one derivative
(2017) A. Srivastava; V.K. Singh; S. Patnaik; J. Tripathi; P. Singh; G. Nath; R.K. Asthana
Aims: Explorations of freshwater Cyanobacteria as antimicrobial (bacteria, fungi and methicillin-resistant Staphylococcus aureus (MRSA) strains) drug resource using bioassay, NRPS (non-ribosomal polypeptide synthetase) and PKS (polyketide synthase) genes, as well as in silico approach. Methods and Results: We have bioassayed the extracts of Phormidium CCC727, Geitlerinema CCC728, Arthrospira CCC729, Leptolyngbya CCC732, Phormidium CCC730, Phormidium CCC731 against six pathogenic bacteria comprising Gram (+ve): S. aureus including seven clinical MRSA and Enterococcus faecalis, Gram (−ve): Escherichia coli, Salmonella Typhimurium, Klebsiella pneumoniae and Shigella boydii along with non-pathogenic Enterobacter aerogenes as well as fungal strains (Cryptococcus neoformans and Candida albicans, C. krusei, C. tropicalis and Aspergillus niger) exhibiting antimicrobial potential. The NRPS and PKS genes of the target strains were also amplified and sequenced. The putative protein structures were predicted using bioinformatics approach. Conclusion: PKS gene expression indicated β keto-acyl synthase as one of the important active domains in the biomolecules related to antitumour and antifungal group. The simultaneous identification of the biomolecule (dihydro-2H-pyran-2-one derivative) was also inferred spectroscopically. Significance and Impact of the Study: Freshwater Cyanobacteria are prolific producers of secondary metabolite(s) that may act as the antimicrobial drug resource in addition to their much explored marine counterpart. © 2016 The Society for Applied Microbiology
Assesment of bioactivity of a Fischerella species colonizing Azadirachta indica (neem) bark
(Corvinus University of Budapest, 2006) S.K. Trigun; A.P. Singh; R.K. Asthana; S.M. Pandey; P. Pandey; S.K. Singh; S.P. Singh
In order to investigate whether a. Fischerella sp. colonizing Azadirachta indica (neem) bark is able to show, like neem derived extracts/products, bioactivity with respect to glucose metabolizing potential in animal models, laboratory cultivated neem colonized cyanobacterial biomass was fed to mice and its effects on liver lactate dehydrogenase (LDH: a key enzyme of glucose metabolism) vis a vis blood glucose level was monitored. Neem bark extract and purified azadirachtin (a bioactive neem product) were also tested simultaneously for comparison. As compared to the control, none of the samples could produce much variation in blood glucose levels except a transitory decline, 34% and 26% at 2nd & 12th h, in azadirachtin and Fischerella (isolated from neem) fed mice respectively. However, all the test samples showed significant increase in liver LDH activity after 2nd h of treatment (p< 0.01) followed by a decline at 6th h. Thereafter, the enzyme activity increased progressively up to 24th h in mice fed with azadirachtin and neem colonized Fischerella only (p < 0.001 at 24th h). Expression pattern of the enzyme was also studied using polyacrylamide gel electrophoresis. Liver specific M4-LDH (homo-tetramer of M sub-unit) was detected in all the cases and time-dependent changes in expression of the enzyme paralleled the alterations observed in its activities. To ascertain whether such a bioactivity is common with Fischerella sp. colonizing other trees also, liver LDH profile was compared between mice fed with Fischerella isolated from neem and jamun (Eugenia jambolana) barks separately. Though Fischerella from jamun did not alter liver LDH profile, Fischerella isolated from neem could produce significant increase in the enzyme activity (p < 0.001) and corresponding changes in the expression of LDH isozymes. The results suggest that Fischerella sp. inhabiting neem bark, like bioactivity of its host plant products, modulates activity and expression of liver LDH in mice. © 2005, Penkala Bt.
Biohydrogen production from cheese whey wastewater in a two-step anaerobic process
(2012) Pankaj K. Rai; S.P. Singh; R.K. Asthana
Cheese whey-based biohydrogen production was seen in batch experiments via dark fermentation by free and immobilized Enterobacter aerogenes MTCC 2822 followed by photofermentation of VFAs (mainly acetic and butyric acid) in the spent medium by Rhodopseudomonas BHU 01 strain. E. aerogenes free cells grown on cheese whey diluted to 10 g lactose/L, had maximum lactose consumption (∼79%), high production of acetic acid (1,900 mg/L), butyric acid (537.2 mg/L) and H2 yield (2.04 mol/mol lactose; rate,1.09 mmol/L/h). The immobilized cells improved lactose consumption (84%), production of acetic acid (2,100 mg/L), butyric acid (718 mg/L) and also H2 yield (3.50 mol/mol lactose; rate, 1.91 mmol/L/h). E. aerogenes spent medium (10 g lactose/L) when subjected to photofermentation by free Rhodopseudomonas BHU 01 cells, the H 2 yield reached 1.63 mol/mol acetic acid (rate, 0.49 mmol/L/h). By contrast, immobilized Rhodopseudomonas cells improved H2 yield to 2.69 mol/mol acetic acid (rate, 1.87 mmol/L/h). The cumulative H2 yield for free and immobilized bacterial cells was 3.40 and 5.88 mol/mol lactose, respectively. Bacterial cells entrapped in alginate, had a sluggish start of H2 production but outperformed the free cells subsequently. Also, the concomitant COD reduction for free cells (29.5%) could be raised to 36.08% by immobilized cells. The data suggest that two-step fermentative H 2 production from cheese whey involving immobilized bacterial cells, offers greater substrate to- hydrogen conversion efficiency, and the effective removal of organic load from the wastewater in the long-term. © Springer Science+Business Media, LLC 2011.
Biohydrogen production from sugarcane bagasse by integrating dark- and photo-fermentation
(Elsevier Ltd, 2014) Pankaj K. Rai; S.P. Singh; R.K. Asthana
Hydrogen production from sugarcane bagasse (SCB) by integrating dark-fermentation by Enterobacter aerogenes MTCC 2822 and photo-fermentation by Rhodopseudomonas BHU 01 was investigated. The SCB was hydrolysed by sulphuric acid and the hydrolysate detoxified by passing through adsorbent resin column (Amberlite XAD-4) to remove the inhibitory furfural, and subjected to dark-fermentation. The cellulosic residue from acid hydrolysis was hydrolysed by the new isolate Cellulomonas fimi to release sugars for H2 production by E. aerogenes, through simultaneous saccharification, filtration and fermentation (SSFF). Cumulative H2 production during dark-fermentation and SSFF was 1000 and 613ml/L, respectively. The spent media of dark-fermentation and SSFF were utilized for photo-fermentation by Rhodopseudomonas BHU 01. The cumulative H2 production was 755ml/L for dark-fermentation and 351ml/L for SSFF spent medium. © 2013 Elsevier Ltd.
Calcium-boron interaction in exopolysaccharide production by the cyanobacterium, Nostoc spongiaeforme
(2000) Neetu Singh; R.K. Asthana; S.P. Singh
The effect and interaction of Ca and B on exopolysaccharide (EPS) synthesis in the diazotrophically growing cyanobacterium, Nostoc spongiaeforme, was investigated. The absence of B inhibited EPS synthesis 1.56-fold (16 μg glucose equivalent/mg dry weight, 16 d) over the control cells (25 μg glucose equivalent) grown in medium containing 0.5 mM Ca and 8 μM B. When B concentration was raised to 40 μM, EPS production was stimulated 1.8-fold. Reduction of Ca concentration to one-half (0.25 mM) resulted in increased B demand (16 μM) by the cells for EPS production at par with the normal sets. However, without Ca, EPS production also increased as B increased. Addition of B to a Ca-free medium stimulated cyanobacterial diazotrophic growth as well as synthesis of Chl a and phycocyanin (0- 8 d). The data suggest B-dependent diazotrophic growth during Ca-deficiency and point to an important interactive role of Ca and B in regulation of cyanobacterial EPS synthesis.
Characterization of an exopolysaccharide mutant of Nostoc spongiaeforme: Zn2+-sorption and uptake
(2003) Neetu Singh; R.K. Asthana; S.P. Singh
Exposure of the exopolysaccharide (EPS)-synthesizing cyanobacterium Nostoc spongiaeforme to Zn2+ (20 μM) transformed the biomass into white debris. However, a few blue-green pin-heads emerged after 2 weeks in the same Zn2+-containing medium and formed less mucoid microcolonies (1-2 mm) relative to the protruding colonies (2-4 mm) of the parent strain on nutrient agar. One of such survivors (designated as Zn20) that was stable through 10 successive transfers in Zn2+-lacking medium has been adopted for further characterization. The parent strain retained almost 88% of the total EPS synthesized, the rest being released into the ambient medium, while for Zn20, the EPS retained approximated to 74%. Although the Zn2+-sensitivity of the mutant was comparable with that of the parent (LD50, 7 μM), Zn2+ uptake was still 5-fold higher in the former (2 μg mg-1 biomass dry wt., 20 μM, external concentration). Also, both the strains showed insignificant difference in Zn2+-sorption onto their isolated EPS. The mutant was characterized by having higher cell carbohydrate content (642.8 μg mg -1 dry wt.) than its parent (513.6 μg). The X-ray diffraction pattern revealed Zn2+ deposition on EPS from the parent mainly as zinc hypophosphite monohydrate [Zn(H2PO2) 2·H2O], whereas there was a lack of distinct peaks in similar samples from Zn20, thus confirming the amorphous nature. There was participation in Zn2+ binding of only COO-, N=O, NO2, SO2 groups in the parent while participation of P-O and C=O groups in mutant EPS was evident in IR spectra. The observations suggest that the mutant could be deployed to achieve sustained EPS synthesis, its release and metal sorption/desorption in repeated cycles.
Copper uptake and its compartmentalization in Pseudomonas aeruginosa strains: Chemical nature of cellular metal
(1999) Sufia K. Kazy; Pinaki Sar; R.K. Asthana; S.P. Singh
Copper-sensitive (Cu5) and copper-resistant (Cu1) strains of Pseudomonas aeruginosa were characterized in terms of Cu2+ sensitivity, uptake and its compartmentalization in the possible cell sectors. Minimum inhibitory concentrations (MICs) of Cu2+ for the Cur strain (3.2 mM and 0.12 mM in enriched- and in minimal-medium, respectively) were almost 5-fold higher over that of its sensitive counterpart. While Cu(s) strain accumulated Cu2+ to a maximum of 1.8 μmol mg-1 protein, Cu(r) strain increased it to 2.37 μmol mg-1 protein. Both the strains also demonstrated energy- and pH-dependent Cu2+ uptake through the broad-substrate range divalent cation (Zn2+, Mg2+, Co2+) uptake system as well as through the system specific for Cu2+. Cell-fractionation study revealed that in Cu(r) strain, periplasm and membrane are the main Cu2+ binding sites, whereas, in case of Cu(s) strain, it is the cytoplasm. The overall observations indicate that the Cur strain restricted Cu2+ sequestration exterior to the cytoplasm as the possible strategy for Cu-resistance. The chemical nature of Cu2+ deposition in the respective strains was also ascertained by X-ray powder diffraction analysis.
Gene expression in the cyanobacterium Anabaena sp. PCC7120 under desiccation
(2004) H. Katoh; R.K. Asthana; M. Ohmori
The N2-fixing cyanobacterium Anabaena sp. PCC7120 showed an inherent capacity for desiccation tolerance. A DNA microarray covering almost the entire genome of Anabaena was used to determine the genome-wide gene expression under desiccation. RNA was extracted from cells at intervals starting from early to late desiccation. The pattern of gene expression in DNA fragments was categorized into seven types, which include four types of up-regulated and three types of down-regulated fragments. Validation of the data was carried out by RT-PCR on selected up-regulated DNA fragments and was consistent with the changes in mRNA levels. Our conclusions regarding desiccation tolerance for Anabaena sp. PCC7120 are as follows: (i) Genes for osmoprotectant metabolisms and the K+ transporting system are upregulated from early to mid-desiccation; (ii) genes induced by osmotic, salt, and low-temperature stress are up-regulated under desiccation; (iii) genes for heat shock proteins are up-regulated after mid-desiccation; (iv) genes for photosynthesis and the nitrogen-transporting system are down-regulated during early desiccation; and (v) genes for RNA polymerase and ribosomal protein are down-regulated between the early and the middle phase of desiccation. Profiles of gene expression are discussed in relation to desiccation acclimation.
Green synthesis of gold nanoparticles from Dunaliella salina, its characterization and in vitro anticancer activity on breast cancer cell line
(Editions de Sante, 2019) Ankit Kumar Singh; Ratnakar Tiwari; Vikas Kumar Singh; Prabhakar Singh; Sk Riyazat Khadim; Urmilesh Singh; Laxmi; Vikas Srivastava; S.H. Hasan; R.K. Asthana
An ecofriendly and efficient method (photoinduced) has been used for green synthesis of stable gold nanoparticles (AuNPs) using aqueous extract as a reducing and stabilizing agent, derived from halotolerant microalga Dunaliella salina. Synthesis of AuNPs was confirmed by UV–Vis spectroscopy showing sharp SPR band at 560 nm after 30 min exposure of sunlight. The synthesis was optimized further as exposure(75min) to sunlight, aqueous extract of Dunaliella (AED) inoculum dose(30%) and HAuCl 4 .xH 2 O (1 mM). The presence of nearly spherical shape of AuNPs with average size of 22.4 nm and crystalline nature were confirmed by TEM, SAED and XRD analysis. The XPS analysis of AuNPs showed presence of two individual peaks at 85.17 and 88.94eV that attributed to Au 4f7/2 and Au 4f5/2 respectively. Phycochemical analysis of AED demonstrated presence of phenolics, flavonoids, tannin and proteins. AED when subjected to SDS-PAGE showed protein bands of 92 and 66 KDa. AuNPs were tested for anticancer activity on MCF7 (cancer) and MCF 10A (normal) cell lines, keeping commercial drug cisplatin as positive control. AuNPs selectively killed cancer cells and were not detrimental to the normal cell line whereas cisplatin killed normal cells also at 48 h exposure, therefore, such AuNPs may be used as an anticancer agent. © 2019 Elsevier B.V.
Identification and structure elucidation of antimicrobial compounds from Lyngbya aestuarii and Aphanothece bullosa
(Cellular and Molecular Biology Association, 2014) M. Kumar; P. Singh; J. Tripathi; A. Srivastava; M.K. Tripathi; A.K. Ravi; R.K. Asthana
Cyanobacteria are known to produce array of compounds. In an earlier report, we reported antibacterial and antifungal activities in methanolic crude extracts of laboratory grown Lyngbya aestuarii and Aphanothece bullosa isolated from Chilka Lake and local paddy field respectively. In this report the same methanolic crude extracts were subjected to TLC purification twice by altering the solvents and UV-illuminated bands bioassayed. Such UV illuminated potent bands obtained after 2nd TLC were subjected to spectroscopic analysis (UV, IR, 1H NMR and LCMS/MS). We have screened malyngolide and dragonamide C from L. aestuarii and a diterpenoid and majusculoic acid from A. bullosa. Dragonamide C and malyngolide were found to be antifungal while majusculoic acid and a diterpenoid as antibacterial. As far as our knowledge goes, this is the first ever report where fresh water A. bullosa was found to be a source of diterpenoid and majusculoic acid. Likewise, L. aestuarii was also established as a source of malyngolide and dragonamide C. This again indicated that cyanobacteria are inherently endowed with the capacity to produce metabolites according to niche and species specific manner emphasising fresh water cyanobacterial strain are as important as marine one. © 2014.
Investigations on nickel biosorption and its remobilization
(1995) R.K. Asthana; S. Chatterjee; S.P. Singh
Immobilized preparations of the bacteria (Pseudomonas aeruginosa and Rhodopseudomonas BHU strain 1) and the cyanobacterium (Anacystis nidulans) exhibited significant Ni adsorption in the order 91%, 72%, 75%, respectively, within 2 h contact with aqueous NiCl2 (7·05 μg Ni/0·1 mg biomass). The immobilizing agent (Ca-alginate, 1·5%, w/v) absorbed more Ni (43%) than the exopolysaccharide of cyanobacteria, Rivularia sp. (40%) of Aphanothece sp. (30%). Ni remobilization from different adsorbed systems was maximum (84%) for Ca(NO3)2 over NaCl (4·3%) at equimolar concentrations (12 mM, each). Extracts from forest soil (organic C, 2-3%) were more effective in Ni remobilization (22·65%) than similar preparations from garden soil (18%) with organic C in the range of 0·98-1·1%. © 1995.
Metal adsorption and desorption by lyophilized Pseudomonas aeruginosa
(1999) P. Sar; S.K. Kazy; R.K. Asthana; S.P. Singh
Biosorption of nickel (Ni2+) and copper (Cu2+) by lyophilized Pseudomonas aeruginosa cells was investigated based on Freundlich isotherm. Bacterial biomass showed significant sorption of both Ni (265 mg g-1) or Cu (137.6 mg g-1), and was also superior over the cation exchanger, IRA 400 (98 mg Ni g-1 or 26.6 mg Cu g-1). Metal binding by the test organism was a fast saturating, pH-dependent process. The optimum pH for Cu adsorption was 7.0 and for Ni 8.0. X-ray diffraction studies revealed that both cations were deposited on the cell predominantly as phosphide crystals. The participation of carboxyl, carbonyl, and phosphoryl groups along with H-bonding in metal sorption was evident in IR spectra. Biomass pretreatment by agents like NaOH, NH4OH or toluene enhanced the metal loading capacity, whereas, oven heating (80°C), autoclaving (120°C, 15 lb (in.2)-1), acid, detergent and acetone treatments were inhibitory. In bimetallic combination, Na, K or Ca increased sorption of Ni as well as Cu in contrast to Cd or Pb. Mineral acids (HCl, H2SO4 and HNO3) and NTA could recover more than 75% (on average) Ni or Cu adsorbed on the biomass. Calcium carbonate (10 mM) was efficient in Ni desorption (71%) compared to Cu (57%). Noticeably sodium carbonate remained specific for Cu remobilization (88%) than Ni (21%). The data are in favour of deployment of the test biomass as an efficient metal removal/recovery system.
Metal removal by selected sorbents
(Elsevier BV, 1996) S. Chatterjee; R.K. Asthana; A.K. Tripathi; S.P. Singh
The sorption of Ni from aqueous solution using fly ash, CaCO3 and sawdust preparations from pine (Pinus roxburghii) and cedar (Cedrus deodara) was investigated. Fly ash with a total of 90% Ni removal, was superior to CaCO3, (55%), sawdust from cedar (63%) or pine (41%) within 30 min. Fly ash was also an effective sorbent for Cd (79%) and Cu (75%). Ni was sequestered significantly by the dead biomass of Pseudomonas (60%) or Nostoc (41%) or Rhodopseudomonas (35%). Freundlich constants (KF) based on the Freundlich isotherm of all the sorbents were in the sequence: fly ash (213.8) > Pseudomonas (169.8) > Nostoc (131.8) > sawdust from cedar (64.57) > CaCO3 (56.23) > Rhodopseudomonas (51.29) > sawdust from pine (44-67). The observations indicate the possible cost-effective deployment of fly ash, carbonates of calcium and plant parts with native resins as metal sorbents. Copyright © 1996 Elsevier Science Ltd. All rights reserved.
Metal uptake and thiol production in Spirodela polyrhiza (L.) SP20
(Elsevier GmbH, 1999) Sanjula Pandey; R.K. Asthana; Arvind M. Kayastha; Neetu Singh; S.P. Singh
Spirodela polyrhiza (L.) SP20 was hypersensitive to Cu (1-100 μmol/L) compared with Ni (25-500 μmol/L). Lower Cu concentration (1 μmol/L) or Ni (25 μmol/L) stimulated general growth of the test organism compared with toxicity at elevated concentrations of both of the cations. Cu uptake was very fast during the first 10 min and remained stable irrespective of the extension of incubation. Ni uptake also showed concentration- and time-dependence, with saturation only at 40 h. If compared at equimolar concentration (100 μmol/L, each), Cu accumulated to the extent of 2.7 mg g-1 dw, a value in close proximity with that of Ni (2.84 mg g-1 dw). At lower concentrations, both of the cations showed high accumulation in root; however, the root/top ratio for either Ni or Cu decreased at elevated concentrations, indicating that the metal(s) could be translocated only after a threshold limit of accumulation in the root. The hypertoxic Cu was also the effective inducer of thiol biosynthesis in the test plant as 10 μmol/L Cu increased it to 15 μmol thiol g-1 dw (10 h) over the metal-less control (10.26 μmol). A 10-fold higher Ni concentration (100 μmol/L) was, however, needed to achieve the same level of thiol. Thiol biosynthesis was also correlated with the intracellular buildup of Cu or Ni.
Nickel effects on phosphate uptake, alkaline phosphatase, and ATPase of a cyanobacterium
(Springer-Verlag, 1992) R.K. Asthana; S.P. Singh; R.K. Singh
[No abstract available]
Nickel uptake and its localization in a cyanobacterium
(1992) A.L. Singh; R.K. Asthana; S.C. Srivastava; S.P. Singh
Nickel bioconcentration in different cell preparations of the cyanobacterium Nostoc muscorum was examined. A two- or three-fold increase in phosphate concentration over that prescribed in growth medium (58 μM), favoured nickel accumulation restricted to a threshold limit. Intact cells showed highest nickel bioconcentration (8.41 μmol mg-1 dry wt) over spheroplasts (6.19 μmol mg-1 dry wt) or polyphosphate bodies (5.88 μmol mg-1 dry wt). Such preparations derived from similar cells indicate that the cyanobacterial cell wall could accommodate around 14-19% of the total nickel taken in by the cell with the overall nickel-bioconcentration sequence as: intact cells > spheroplasts > polyphosphate bodies > cell wall. The data suggest that polyphosphate bodies are the main sink for nickel. © 1992.
One pot hydrothermal synthesis of fluorescent NP-carbon dots derived from Dunaliella salina biomass and its application in on-off sensing of Hg (II), Cr (VI) and live cell imaging
(Elsevier B.V., 2019) Ankit Kumar Singh; Vikas Kumar Singh; Mamata Singh; Prabhakar Singh; Sk. Riyazat Khadim; Urmilesh Singh; Biplob Koch; S.H. Hasan; R.K. Asthana
The impact of hazardous chemicals and toxic metal ions in the environment played havoc to the ecosystem. In the present work green chemistry approach was applied for one-step hydrothermal synthesis of nitrogen, phosphorus dual doped carbon dots, utilizing green precursor i.e, biomass of halophilic microalgae Dunaliella salina (algal derived nitrogen phosphorous carbon dots i.e A-NPCDs). Synthesized A-NPCDs were characterized through TEM, FT-IR, P-XRD, DLS and XPS. It showed appreciable optical properties with significant fluorescence quantum yield (8%)and exhibited blue color under UV – light (λ ex = 365 nm). A-NPCDs acted as fluorescent turn off sensor for toxic metal ion such as Hg (II) and Cr (VI) with good selectivity and sensitivity. Interestingly, ANPCDs detected Cr (VI) up to 0.018μM which was below the permissible level of Cr (VI) in drinking water. Such sensing resulted because of combination of inner filter effect and dynamic quenching mechanism. Moreover, it also showed good selectivity (0.018μM) for Hg (II) via dynamic quenching mechanism. MTT assay of A-NPCDs on HEK-293 cell line showed biocompatibility with negligible cytotoxicity. Therefore, these were successfully employed for live cell imaging and intracellular detection of Hg (II) and Cr (VI) in HEK-293 cell line. Thus, green synthesized A-NPCDs may be a good alternative for chemically derived CDs in intracellular detection of Hg (II) and Cr (VI) of a complex biological environment. © 2019
Optimization of photo-hydrogen production based on cheese whey spent medium
(Elsevier Ltd, 2014) Pankaj K. Rai; R.K. Asthana; S.P. Singh
Cheese whey wastewater diluted to 10 g lactose/L was initially subjected to dark-fermentation by Enterobacter aerogenes MTCC 2822, and the VFAs-rich spent medium (acetic acid 1900 mg/L, butyric acid 537 mg/L, and traces of propionic acid) was subjected to photo-fermentation through enrichment by Ni2+ (0-8 μmol/L), Fe2+ (0-100 μmol/L) or Mg2+ (0-15 mmol/L) in batch mode by Rhodopseudomonas BHU 01 strain. The maximum cumulative H2 production (144 ml) and yield (58 mmol) was obtained at 4 μmol Ni2+/L. Likewise, Fe2+ (60 μmol/L) resulted in maximum cumulative H2 production (139 ml) and yield (56 mmol). Nevertheless, 6 mmol of Mg2+ did not significantly affect H2 production (110 ml) or yield (44 mmol); the latter value in close proximity with the control (37 mmol). The concomitant reduction in COD was maximum (15.61%) for 4 μmol Ni2+/L, followed by 15.33% for 60 μmol Fe2+/L, and the least for 6 mmol Mg2+/L (14.5%). The observations suggest the role of Fe2+ and Ni2+ in regulation of nitrogenase and hydrogenase, while that of Mg2+ mainly in the biosynthesis of photopigment bacteriochlorophyll (Bchl). © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.