Hydroxyapatite nanoparticles (HAp NPs) were synthesized with Muntingia calabura leaf extract as solvent and eggshell waste as a calcium source. The synthesized nanoparticles were irregular rod-like, ...as visualized by FESEM, while EDX and XPS studies confirmed the formation of hydroxyapatite. The synthesized HAp NPs were polycrystalline and highly thermostable as per XRD and TGA studies respectively. FTIR confirmed the stable coating of plant phytochemicals onto the HAp NPs. Congo red adsorption using HAp NPs nanoadsorbent was optimized by central composite design, wherein 89.96% of 33.18 mg/L dye was adsorbed in 137 min at 180 RPM. The adsorption process was in line with pseudo-second-order model and the Freundlich isotherm indicated chemical adsorption. The adsorption process was feasible, exothermic, and spontaneous as indicated by the thermodynamic studies. The adsorption capacity of HAp NPs stood at a maximum of 217 mg/g, indicating its superiority among other adsorbents reported earlier. It is evident from the convincing results that the HAp NPs synthesized in the present investigation may have a major role in developing novel adsorbents for dye removal out of wastewater streams.
The present study aimed at the synthesis of cobalt oxide nanoparticles (CONPs) mediated by leaf extract of Muntingia calabura using a rapid and simple method and evaluation of its photocatalytic ...activity against methylene blue (MB) dye. UV–vis absorption spectrum showed multiple peaks with an optical band gap of 2.05 eV, which was concordant with the literature. FESEM image signified the irregular-shaped, clusters of CONPs, and EDX confirmed the existence of the Co and O elements. The sharp peaks of XRD spectrum corroborated the crystalline nature with a mean crystallite size of 27.59 nm. Raman spectrum substantiated the purity and structural defects. XPS signified the presence of Co in different oxidation states. FTIR image revealed the presence of various phytochemicals present on the surface and the bands at 515 and 630 cm−1 designated the characteristic Co–O bonds. VSM studies confirmed the antiferromagnetic property with negligible hysteresis. The high BET specific surface area (10.31 m2/g) and the mesoporous nature of the pores of CONPs signified the presence of a large number of active sites, thus, indicating their suitability as photocatalysts. The CONPs degraded 88% of 10 mg/L MB dye within 300 min of exposure to sunlight. The degradation of MB dye occurred due to the formation of hydroxyl free radicals on exposure to sunlight, which followed first-order kinetics with rate constant of 0.0065 min−1. Hence, the CONPs synthesized herein could be applied to degrade other xenobiotics and the treatment of industrial wastewater and environmentally polluted samples.
•Cobalt oxide nanoparticles were synthesized using Muntingia calabura leaf extract – green synthesis method.•Irregular nano-aggregates were witnessed in FE-SEM image.•XRD, XPS and Raman studies signified the crystallinity of the Co3O4 nanoparticles.•Photocatalytic potential of Co3O4 nanoparticles was demonstrated for methylene blue dye.
Use of novel biological materials as adsorbents for removal of xenobiotics is gaining significance owing to their exceptional advantages. An extracellular polymeric substance (EPS) produced by ...Lysinibacillus sp. SS1 had rough porous surface as observed by SEM analysis. Adsorption ability of EPS was estimated against various textile dyes such as Malachite Green (MG), Methyl Orange, Congo Red and Coomassie Blue. About 82% of MG (100 mg/L) was adsorbed onto 2.5 mg EPS within 30 min. Effect of MG concentration, EPS weight, agitation speed and incubation time on adsorption, studied by one factor at a time approach, revealed that adsorption was influenced by all factors. Maximum adsorption of 99.01 ± 0.61% was achieved at 100 mg/L MG, 10 mg EPS, 120 RPM in 75 min with maximum adsorption capacity of 247.5 mg/g. Kinetics was affected by MG and EPS amounts, with shift from pseudo first to pseudo second order with increase in concentration. Adsorption of MG by EPS of Lysinibacillus sp. SS1 was identified as unilayer chemisorption as it followed Langmuir isotherm with maximum adsorption capacity (Qm) of 178.57 mg/g (R2 = 0.9889). This is the first report on potential of EPS produced by Lysinibacillus sp. SS1 as novel biodegradable adsorbent with high efficacy of MG removal from aqueous solutions.
EPS, Lysinibacillus sp. SS1, Malachite Green, Adsorption kinetics.
Effect of oil spills on living forms demands for safe, ecofriendly and cost-effective methods to repair the damage. Pseudomonads have exceptional tolerance to xenobiotics and can grow at varied ...environmental conditions. This study aims at biosurfactant mediated degradation of petroleum crude oil by an indigenous Pseudomonas sp. WD23 in sea water. Pseudomonas sp. WD23 degraded 34% of petroleum crude oil (1.0% v/v) on supplementation of yeast extract (0.05 g/L) with glucose (1.0 g/L) in seawater. The strain produced a biosurfactant which was confirmed as a rhamnolipid (lipid: rhamnose 1:3.35) by FT-IR, LCMS and quantitative analysis. Produced rhamnolipid had low CMC (20.0 mg/L), emulsified petroleum oils (75–80%) and had high tolreance to varied conditions of pH, temperature and ionic strength. OFAT studies were performed to analyse the effect of petroleum crude oil, glucose, inoculum, yeast extract, pH, agitation speed and incubation time on degradation by Pseudomonas sp. WD23. Petroleum crude oil and glucose had significant effect on biodegradation, rhamnolipid production and growth, further optimized by central composite design. At optimum conditions of 3.414% v/v PCO and 6.53 g/L glucose, maximum degradation of 81.8 ± 0.67% was observed at pH 7.5, 100 RPM, 15.0% v/v inoculum in 28 days, with a 3-fold increase in biodegradation. GCMS analysis revealed degradation (86–100%) of all low and high molecular weight hydrocarbons present in petroleum crude oil. Hence, the strain Pseudomonas sp. WD23 can be effectively developed for management of oil spills in seas and oceans due to its excellent degradation abilities.
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•Indigenous Pseudomonas sp. WD23 utilizes petroleum crude oil as sole carbon source in seawater.•Degradation aided by secreted mono-rhamnolipid with exceptional physico-chemical properties.•Degradation of 81.8 ± 0.67% of 3.41% v/v of petroleum crude oil in seawater in 28 days on optimization by CCD.•C8–C26+ hydrocarbons degraded as per GC-MS analysis.
Intracellular lipase from Enterococcus faecium MTCC5695 (MTCC5695), a lactic acid bacterium, grown at optimal conditions was subjected to purification and concentration using aqueous two-phase ...extraction system (ATPS). The partitioning behavior was studied for five different phase forming salts. Molecular weight of polyethylene glycol (PEG), concentration of PEG and phase forming salt, tie line length (TLL) and phase volume ratio were optimized for the purification of E. faecium lipase. Partitioning occurred towards bottom phase of the system containing sodium dihydrogen phosphate. The optimum conditions for purification were at PEG 8000, 41.24% TLL and 0.25 phase volume ratio. Activity recovery and purification factor achieved after ultrafiltration were 5.99% and 82.09%, respectively. In addition, enzyme characterization studies revealed that MTCC5695 produced an alkaline lipase. Molecular weight of the purified lipase was about 19.2kDa; and, the purified lipase had optimal activity at pH 10.8 and 40°C. Stability over different pH and temperature ranges along with the effect of variety of organic solvents is also reported. Studies involving group specific modifiers indicated the role of histidine, serine, carboxylate and tryptophan in the catalytic site, which is a characteristic feature of lipases.
•Kleibsiella pneumoniae Kpn555 tolerates 900 mg/L lead.•SEM and TEM studies revealed surface deposition and bioaccumulation of lead.•Surface deposition mediated by EPS produced in response to lead ...stress, characterised as glycolipid with protein moieties.•Maximum biosorption ability of EPS – 475 mg/g.•Ability of lead bioaccumulation is plasmid mediated.
Kleibsiella pneumoniae Kpn555, isolated from coffee waste pulp showed high level of tolerance to lead with a minimum inhibitory concentration of 900 mg/L. On its growth in nutrient broth supplemented with lead, brown clumps were visualised at the bottom of the flask. On scanning and transmission electron microscopic studies the brown clumps were corroborated to be bacterial cells with lead biosorbed on the cell surface and accumulated inside the cytoplasm. Biochemical and FT-IR analysis of the extracellular polymeric substance produced on exposure to lead revealed its chemical nature as glycolipid with protein moieties. Purified EPS (100 mg/L) could remove 50% of lead from aqueous solution (200 mg/L). Isolation of plasmid from Klebsiella pneumoniae Kpn555 revealed the presence of a plasmid of size 30–40 kb. This capability of the bacteria was proven to be plasmid mediated as the Escherichia coli DH5α cells transformed with the plasmid of Klebsiella pneumoniae Kpn555 also could tolerate 900 mg/L of lead and form brown clumps. This study shows that these bacteria, aided by EPS could serve as an effective agent for the removal of lead from contaminated water environmental samples.
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Petroleum crude oil is transported on a global scale through marine vessels and barges by the sea route. Oil spills into the marine environment are known to cause long term effects on the health of ...marine life and human beings in addition to harming the eco-system. In this study, petroleum refinery effluent samples were collected and analyzed for their physico-chemical properties. Thirty two bacterial strains were isolated by direct isolation and post enrichment in crude oil. Among these, fourteen isolates could utilize petroleum hydrocarbons as sole carbon source on Bushnell Hass Agar plates supplemented with crude oil within 2 days. Out of these fourteen strains, four could decolorize 2,6-dichlorophenol indophenol within 36 h completely. They were identified as Bacillus cereus WD22, Pseudomonas aeruginosa WD23 and WDE11 (2 strains) and Acinetobacter baumannii OCB1 by 16sRNA sequencing. All four strains could tolerate salinity up to 4.0%w/v. The reduction in total petroleum hydrocarbons in sea water spiked with crude oil (1.0%v/v) supplemented with trace amounts of glucose and yeast extract was studied by gravimetric analysis. P. aeruginosa WD23 degraded 27.25% of supplied petroleum crude oil under limited nutrient conditions in seawater in 15 days. Keywords: petroleum crude oil, sea water, petroleum refinery effluent, Acinetobacter baumannii, Bacillus cereus, Pseudomonas aeruginosa
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Benzo(a)pyrene, a five-ring polyaromatic hydrocarbon, originating from coal tar, crude oil, tobacco, grilled foods, car exhaust etc, is highly persistent in the environment. It has been classified as ...a Group I carcinogen, as on its ingestion in human body, diol epoxide metabolites are generated, which bind to DNA causing mutations and eventual cancer. Among various removal methods, bioremediation is most preferred as it is a sustainable approach resulting in complete mineralization of benzo(a)pyrene. Therefore, in this study, biodegradation of benzo(a)pyrene was performed by two strains of Pseudomonas, i. e WDE11 and WD23, isolated from refinery effluent. Maximum benzo(a)pyrene tolerance was 250 mg/L and 225 mg/L against Pseudomonas sp. WD23 and Pseudomonas sp. WDE11 correspondingly. Degradation rate constants varied between 0.0468 and 0.0513/day at 50 mg/L with half-life values between 13.5 and 14.3 days as per first order kinetics, while for 100 mg/L, the respective values varied between 0.006 and 0.007 L/mg. day and 15.28–16.67 days, as per second order kinetics. The maximum specific growth rate of strains WDE11 and WD23 was 0.3512/day and 0.38/day accordingly, while concentrations over 75 mg/L had an inhibitory effect on growth. Major degradation metabolites were identified as dihydroxy-pyrene, naphthalene-1,2-dicarboxylic acid, salicylic acid, and oxalic acid, indicating benzo(a)pyrene was degraded via pyrene intermediates by salicylate pathway through catechol meta-cleavage. The substantial activity of the catechol 2,3 dioxygenase enzyme was noted during the benzo(a)pyrene metabolism by both strains with minimal catechol 1,2 dioxygenase activity. This study demonstrates the exceptional potential of indigenous Pseudomonas strains in complete metabolism of benzo(a)pyrene.
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•Indigenous Pseudomonas strains utilize benzo(a)pyrene as singular carbon source, degrade over 75% of 100 mg/L in 56 days.•Degradation kinetics is concentration dependent – first-order at lower concentration, second-order at higher concentration.•Growth of Pseudomonas strains is inhibited over 75 mg/L benzo(a)pyrene.•Metabolic intermediates of pyrene, phenanthrene and naphthalene identified.•Salicylate pathway followed by meta cleavage of catechol.
•Photocatalytic water splitting for hydrogen generation.•Reduced Bandgap, minimal electron-hole recombination by use of nanocomposite photocatalysts.•Recent carbon based and metal-based ...nanocomposites.•Implications and future prospects in use of nanocatalysts for H2 production.
Overexploitation of fossil fuels for energy production has impacted the globe tremendously in terms of warming and other environmental issues which is a grave issue of anxiety. An attractive solution would be to produce fuel like hydrogen, which is a clean renewable fuel as its combustion releases only water. Light-based splitting of water for hydrogen production using novel carbon and metal-based nano-catalysts has been the foremost emphasis of this review. The need for paradigm shifts from conventional semiconductors to novel nanocomposites, which could enhance the photocatalytic activity by reducing the recombination rate of photogenerated electron-holes/shortening the charge transfer distance through Z scheme, Type – II and Schottky junction is accentuated with recent advancements in the field. The implications and possible solutions with future perspectives to see hydrogen production technology are also deliberated.
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