A novel and economical approach for the synthesis of short rod-shaped mesoporous silica nanoparticles from coal fly ash waste by Bacillus circulans MTCC 6811.

Coal fly ash (CFA) is an industrial byproduct produced during the production of electricity in thermal power plants from the burning of pulverized coal. It is considered hazardous due to the presence of toxic heavy metals while it is also considered valuable due to the presence of value-added minerals like silicates, alumina, and iron oxides. Silica nanoparticles' demands and application have increased drastically in the last decade due to their mesoporous nature, high surface area to volume ratio, etc. Here in the present research work, short rod-shaped, mesoporous silica nanoparticles (MSN) have been synthesized from coal fly ash by using Bacillus circulans MTCC 6811 in two steps. Firstly, CFA was kept with the bacterial culture for bioleaching for 25 days in an incubator shaker at 120 rpm. Secondly, the dissolved silica in the medium was precipitated with the 4 M sodium hydroxide to obtain a short rod-shaped MSN. The purification of the synthesized silica particle was done by treating them with 1 M HCl at 120 °C, for 90 min. The synthesized short rod-shaped MSN were characterized by UV-vis spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Particle size analyzer (PSA), Field emission scanning electron microscopy (FESEM), and transmission electron microscope. The microscopic techniques revealed the short rod-shaped mesoporous silica nanoparticles (MSN) for the final nano-silica, whose size varies from 40 to 80 nm, with an average size of 36 ± 5 nm. The XRD shows the crystalline nature of the synthesized MSN having a crystallite size of 36 nm. The FTIR showed the three characteristic bands in the range of 400-1100 cm-1, indicating the purity of the sample. The energy dispersive X-ray (EDX) showed 53.04 wt% oxygen and 43.42% Si along with 3.54% carbon in the final MSN. The particle size analyzer revealed that the average particle size is 368.7 nm in radius and the polydispersity index (PDI) is 0.667. Such a novel and economical approach could be helpful in the synthesis of silica in high yield with high purity from coal fly ash and other similar waste.

Nanobioremediation: a bacterial consortium-zinc oxide nanoparticle-based approach for the removal of methylene blue dye from wastewater.

Industrial effluents carrying dyes are considered a major environmental threat in the present era. Methylene blue (MB) dye is one of the key dyes of the thiazine group of dyes. It is broadly used in medical, textile, and various fields and is well known for its carcinogenicity and methemoglobin nature. Bacterial and other microbes-mediated bioremediation is becoming an emerging and significant section for the treatment of wastewater. Isolated bacteria were used for the bioremediation and nanobioremediation of methylene blue dye under varying conditions and parameters. A comparative study was conducted for the remediation of methylene blue dye using bacterial consortium, potential bacteria (isolated by scale-up method), and potential bacteria within zinc oxide nanoparticles. The decolorizing ability of bacteria was analyzed by UV visible spectrophotometer after stirring and static incubation in different time intervals of the isolates. Growth parameters and environmental parameters which include pH, initial dye concentration, and dose of nanoparticles were optimized with the minimal salt medium. An enzyme assay study was also done to check the effect of dye and nanoparticles on bacterial growth and the mode of action of degradation. The authors found that potential bacteria within ZnO nanoparticles showed enhanced decolorization efficiency (95.46% at pH 8) due to the properties of nanoparticles. On the other hand, the decolorization of MB dye by potential bacteria and the bacterial consortium was about 89.08 and 76.3%, respectively, for a 10-ppm dye concentration. During the enzyme assays study, the highest activity was observed for phenol oxidase, nicotinamide adenine dinucleotide (NADH), 2,6-Dichloroindophenol(DCIP), and laccase for nutrient broth having MB dye, MB dye, and ZnO NPs, while no such change was observed for manganese peroxidase enzyme activity. Nanobioremediation is a promising approach to removing such pollutants from the environment.

16S rRNA molecular profiling of heavy metal tolerant bacterial communities isolated from soil contaminated by electronic waste.

Electronic waste is an evolving source of harmful pollutants in our surrounding environments and considered to be perilous as it contains toxic metals such as chromium, cadmium, lead, mercury, zinc, and nickel in huge quantities. Heavy metals are harmful contaminants and accumulated in the environment due to various anthropogenic activities. The present study was conducted to isolate and characterize different heavy metal tolerant bacterial species, based on molecular techniques from soil contaminated by electronic waste. The contaminated soil samples were analyzed for various physicochemical properties such as pH, electrical conductivity, soil moisture, water holding capacity, organic carbon, organic matter, available phosphorus, total nitrogen, and potassium using standard procedures. The soil samples were found to contain a higher amount of different heavy metals such as copper, chromium, lead, iron, cadmium, and nickel. Serial dilution and spread plate techniques have been used for bacterial isolation. The identification and molecular characterization of isolated bacterial species were done by biochemical tests and 16S rRNA gene sequencing technique. The 16S rRNA sequencing analysis confirmed the presence of different bacterial species as, Micrococcus aloeverae, Kocuria turfanensis, Bacillus licheniformis, Bacillus jeotgali, Bacillus velezensis, and Bacillus haikouensis. The findings indicated that the e-waste dumping sites are the storehouse of elite bacterial species. The present research study offers a platform for systematic analysis of e-waste sites by microbial profiling that may help in the innovation of novel microorganisms of scientific importance and better biotechnological potential.

Microbial degradation of petrochemical waste-polycyclic aromatic hydrocarbons.

BACKGROUND: Petrochemical industry is one of the fastest growing industries. This industry has immense importance in the growth of economy and manufacture of large varieties of chemicals. The petrochemical industry is a hazardous group of industry generating hazardous waste containing organic and inorganic compounds. In spite of the present treatment process, the hazardous waste compounds are found untreated to the acceptable level and found discharged at soil-water environment resulting into the persistent organic-inorganic pollutant into the environment. The bioremediation will be the innovative techniques to remove the persistent pollutants in the environment. RESULT: Petrochemical contaminated site was found to be a rich source of microbial consortium degrading polycyclic aromatic hydrocarbons. Indigenous microbial consortiums were identified and used for bioremediation of polycyclic aromatic hydrocarbons (naphthalene and anthracene) at the concentrations of 250, 500, and 750 ppm. The potential microorganism was also identified for naphthalene and anthracene, and their bioremediation was studied at varying concentrations. The bioremediation with consortium was found to be comparatively more effective than the potential microorganism used for bioremediation of each compound. Pseudomonas aeruginosa a potential organism was identified by 16S rRNA and further studied for the gene responsible for the PAH compounds. CONCLUSION: Indigenous microorganism as a consortium has been found effective and efficient source for remediation of organic compound-Polycyclic aromatic hydrocarbon and this will also be applicable to remediate the toxic compounds to clean up the environment.

Mineralization of a sulfonated textile dye Reactive Red 31 from simulated wastewater using pellets of Aspergillus bombycis.

BACKGROUND: Reactive Red 31, applied extensively in the commercial textile industry, is a hazardous and persistent azo dye compound often present in dye manufacturing and textile industrial effluents. Aspergillus bombycis strain was isolated from dye contaminated zones of Gujarat Industrial Development Corporation, Vatva, Ahmedabad, India. The decolorization potential was monitored by the decrease in maximum absorption of the dye using UV-visible spectroscopy. Optimization of physicochemical conditions was carried out to achieve maximum decolorization of Reactive Red 31 by fungal pellets. RESULTS: Pellets of A. bombycis strain were found to decolorize this dye (20 mg/L) under aerobic conditions within 12 h. The activity of azoreductase, laccase, phenol oxidase and Manganese peroxidase in fungal culture after decolorization was about 8, 7.5, 19 and 23.7 fold more than before decolorization suggesting that these enzymes might be induced by the addition of Reactive Red 31 dye, and thus results in a higher decolorization. The lab-scale reactor was developed and mineralization of Reactive Red 31 dye by fungal pellets was studied at 6, 12 and 24 h of HRT (hydraulic retention time). At 12 h of HRT, decolorization potential, chemical oxygen demand (COD) and total organic carbon reduction (TOC) was 99.02, 94.19, and 83.97%, respectively, for 20 mg/L of dye concentration. CONCLUSIONS: Dye decolorization potential of A. bombycis culture was influenced by several factors such as initial dye concentration, biomass concentration, pH, temperature, and required aerated conditions. Induction of azoreductase, laccase, phenol oxidase, and Mn-peroxidase enzymes was observed during dye decolorization phase. A. bombycis pellets showed potential in mineralization of dye in the aerobic reactor system. Isolated fungal strain A. bombycis showed better dye decolorization performance in short duration of time (12 h) as compared to other reported fungal cultures.Graphical abstractDegradation of RR31 dye in developed aerobic fungal pelleted reactor.

Egg shell waste as heterogeneous nanocatalyst for biodiesel production: Optimized by response surface methodology.

Worldwide consumption of hen eggs results in availability of large amount of discarded egg waste particularly egg shells. In the present study, the waste shells were utilized for the synthesis of highly active heterogeneous calcium oxide (CaO) nanocatalyst to transesterify dry biomass into methyl esters (biodiesel). The CaO nanocatalyst was synthesied by calcination-hydration-dehydration technique and fully characterized by infrared spectroscopy, X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), brunauer-emmett-teller (BET) elemental and thermogravimetric analysis. TEM image showed that the nano catalyst had spherical shape with average particle size of 75 nm. BET analysis indicated that the catalyst specific surface area was 16.4 m2 g-1 with average pore diameter of 5.07 nm. The effect of nano CaO catalyst was investigated by direct transesterification of dry biomass into biodiesel along with other reaction parameters such as catalyst ratio, reaction time and stirring rate. The impact of the transesterification reaction parameters and microalgal biodiesel yield were analyzed by response surface methodology based on a full factorial, central composite design. The significance of the predicted mode was verified and 86.41% microalgal biodiesel yield was reported at optimal parameter conditions 1.7% (w/w), catalyst ratio, 3.6 h reaction time and stirring rate of 140.6 rpm. The biodiesel conversion was determined by 1H nuclear magnetic resonance spectroscopy (NMR). The fuel properties of prepared biodiesel were found to be highly comply with the biodiesel standard ASTMD6751 and EN14214.

Biosynthesis of titanium dioxide nanoparticles using Bacillus amyloliquefaciens culture and enhancement of its photocatalytic activity for the degradation of a sulfonated textile dye Reactive Red 31.

The present study aims at exploiting Bacillus amyloliquefaciens for the biosynthesis of titanium dioxide nanoparticles and also investigates role of bacterial enzymes in the biosynthesis of titanium dioxide nanoparticles. Bacterial synthesized as well as metal doped titanium dioxide nanoparticles were characterized by X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDAX). Amylase activity (43.37IU) in culture supernatant evinced a potential involvement of extracellular enzyme in TiO2 nanoparticle biosynthesis. Crystallite size of bio-synthesized nanoparticles was found to be in the range of 15.23-87.6nm. FTIR spectroscopy and native-PAGE (Polyacrylamide Gel Electrophoresis) clearly indicated involvement of alpha amylase in biosynthesis of TiO2 nanoparticles and in their stabilization. TEM micrographs of the synthesized titanium dioxide nanoparticles revealed the formation of spherical nanoparticles with a size range of 22.11-97.28nm. Photocatalytic degradation of Reactive Red 31 (RR31) dye was carried out using bio-synthesized TiO2 nanoparticles under UV radiation. Photocatalytic activity of synthesized nanoparticles was enhanced by Ag, La, Zn and Pt doping. Platinum doped TiO2 showed highest potential (90.98%) in RR31 degradation as compared to undoped (75.83%).

Multifunctionality of rare earth doped nano ZnSb2O6, CdSb2O6 and BaSb2O6: photocatalytic properties and white light emission.

Undoped MSb2O6 (where M = Zn, Cd, Ba) and single and double doped MSb2O6:RE (where RE = Tb(3+) and Eu(3+)) nanophosphors were synthesized through a simple sonochemical process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), diffuse reflectance (DRS) and photoluminescence (PL) spectrophotometry. The TEM micrographs show that the resulting nanoparticles have mostly a spherical shape. Energy transfer was observed from the host to the dopant ions and characteristic green emissions from Tb(3+) ions and red emissions from Eu(3+) ions were observed. The chromaticity diagrams of the ZnSb2O6:Tb(3+)(1.2%):Eu(3+)(0.8%), CdSb2O6:Eu(3+)(0.5%):Tb(3+)(1.5%) and BaSb2O6:Eu(3+)(1%):Tb(3+)(1%) nanophosphors yielded CIE and CCT (correlated color temperature) values in the white light region. The photocatalytic activities of the undoped and double doped antimonates were evaluated for the degradation of rhodamine B (RhB) under UV light. Undoped MSb2O6 (where M = Zn, Cd, Ba) as well as ZnSb2O6:Tb(3+)(1.2%):Eu(3+)(0.8%), CdSb2O6:Eu(3+)(0.5%):Tb(3+)(1.5%) and BaSb2O6:Eu(3+)(1%):Tb(3+)(1%) samples exhibited good photodegradation capacity for RhB. Thus double doped ZnSb2O6:Tb(3+)(1.2%):Eu(3+)(0.8%), CdSb2O6:Eu(3+)(0.5%):Tb(3+)(1.5%) and BaSb2O6:Eu(3+)(1%):Tb(3+)(1%) can be termed a bifunctional material exhibiting both photocatalytic properties and white light emission.

Investigation of potential rhizospheric isolate for cypermethrin degradation.

Rhizoremediation is the use of plant-microbe interaction for the enhanced degradation of contaminants. Rhizosphere bioremediation of pyrethroid pesticides will offer an attractive and potentially inexpensive approach for remediation of contaminated soil. The present study was done with the aim of establishment of highly effective remediation method using plant with degradative rhizosphere and isolation of naturally occurring rhizosphere associated potential degrader providing the possibility of both environmental and insitu detoxification of cypermethrin contamination. The remediation efficacy of Pennisetum pedicellatum was investigated using green house pot culture experiments in cypermethrin amended potting soil mix (10, 25, 50, 75 and 100 mg/kg) for periodic evaluation of changes in concentration. Total proportion of cypermethrin degraders was found to be higher in rhizosphere soil compared to bulk soil. The cypermethrin degrading strain associated with rhizosphere capable of surviving at higher concentrations of cypermethrin was designated as potential degrader. On the basis of morphological characteristics, biochemical tests and 16S rDNA analysis, isolate was identified as Stenotrophomonas maltophilia MHF ENV 22. Bioremediation data of cypermethrin by strain MHF ENV22 examined by HPLC and mass spectroscopy, indicated 100, 50 and 58 % degradation within the time period of 72, 24 and 192 h at concentrations 25, 50 and 100 mg/kg, respectively. This is the first report of effective degradation of cypermethrin by Stenotrophomonas spp. isolated from rhizosphere of Pennisetum pedicellatum. Rhizoremediation strategy will be of immense importance in remediation of cypermethrin residues to a level permissible for technogenic and natural environment.

Chlorpyrifos bioremediation in Pennisetum rhizosphere by a novel potential degrader Stenotrophomonas maltophilia MHF ENV20.

Rhizoremediation is a specific type of phytoremediation involving both plants and their rhizosphere associated microbes. In the present study Pennisetum pedicellatum and rhizosphere associated degrading strains were evaluated for chlorpyrifos remediation. Time-course pot experiments were conducted in greenhouse with P. pedicellatum grown in soil amended with chlorpyrifos at the concentrations of 10, 25, 50, 75 and 100 mg/kg for 60 days. The half life of chlorpyrifos varied from 19.25 to 13.02 days in planted treatments. Residual concentrations of chlorpyrifos were negatively correlated with abundance of degrading microorganisms in rhizosphere. The isolated species of Bacillus, Rhodococcus and Stenotrophomonas were evaluated for their degrading potential in mineral medium. A novel isolated strain of potential degrader Stenotrophomonas maltophilia named as MHF ENV20 showed better survival and degradation at high concentration of chlorpyrifos. Degradation of chlorpyrifos by strain MHF ENV20, 100, 50 and 33.3% degradation within the time period of 48 h (h), 72 and 120 h at 50,100 and 150 mg/kg concentrations, further the gene encoding the organophosphorous hydrolase (mpd) was amplified using PCR amplification strategy and predesigned primers. Our findings indicate that rhizosphere remediation is effective bioremediation technique to remove chlorpyrifos residues from soil. P. pedicellatum itself, in addition to the rhizosphere bacterial consortium, seemed to play an important role in reducing chlorpyrifos level in soil. High chlorpyrifos tolerance and rhizospheric degradation capability of P. pedicellatum, makes this plant suitable for decontamination and remediation of contaminated sites. The ability to survive at higher concentration of chlorpyrifos and enhanced degrading potential due to presence of mpd gene make S. maltophilia MHF ENV20 an ideal candidate for its application in chlorpyrifos remediation.

Bioremediation of heavy metals using biostimulation in laboratory bioreactor.

The present research study investigates bioremediation potential of biostimulated microbial culture isolated from heavy metals waste disposal contaminated site located at Bhayander (east), Mumbai, India. The physicochemical and microbial characterization including heavy metal contaminants have been studied at waste disposal site. The microorganisms adapted at heavy metal-contaminated environment were isolated, cultured, and biostimulated in minimal salt medium under aerobic conditions in a designed and developed laboratory bioreactor. Heavy metals such as Fe, Cu, and Cd at a selected concentration of 25, 50, and 100 µg/ml were taken in bioreactor wherein biostimulated microbial culture was added for bioremediation of heavy metals under aerobic conditions. The remediation of heavy metals was studied at an interval of 24 h for a period of 21 days. The biostimulated microbial consortium has been found effective for remediation of Cd, Cu, and Fe at higher concentration, i.e., 100 mg/l up to 98.5%, 99.6%, and 100%, respectively. Fe being a micronutrient was remediated completely compared to Cu and Cd. During the bioaccumulation of heavy metals by microorganisms, environmental parameters such as pH, total alkalinity, electronic conductivity, biological oxygen demand, chemical oxygen demand, etc. were monitored and assessed. The pilot scale study would be applicable to remediate heavy metals from waste disposal contaminated site to clean up the environment.

Biodegradation of phenanthrene using adapted microbial consortium isolated from petrochemical contaminated environment.

In developing countries like India, there are many industrial areas discharging effluent containing large amount of polyaromatic hydrocarbon (PAH) which causes hazardous effect on the soil-water environment. The objective of this study was to isolate and characterize high-efficiency PAH-degrading microbial consortium from 3 decade old petrochemical refinery field located in Nagpur, Maharashtra with history of PAH disposal. Based on biochemical tests and 16S rDNA gene sequence analysis the consortium was identified as Sphingobacterium sp., Bacillus cereus and a novel bacterium Achromobacter insolitus MHF ENV IV with effective phenanthrene-degrading ability. The biodegradation data of phenanthrene indicates about 100%, 56.9% and 25.8% degradation at the concentration of 100mg/l, 250 mg/l and 500 mg/l respectively within 14 days. The consortium and its monoculture isolates also utilized variety of other hydrocarbons for growth. To best of our knowledge this is the first time that Achromobacter insolitus has been reported to mineralize phenanthrene effectively. GC-MS analysis of phenanthrene degradation confirmed biodegradation by detection of intermediates like salicylaldehyde, salicylic acid and catechol. All the results indicated that the microbial consortium have a promising application in bioremediation of petrochemical contaminated environments and could be potentially useful for the study of PAH degradation and for bioremediation purposes.

Benzene bioremediation using cow dung microflora in two phase partitioning bioreactor.

Bioremediation of benzene has been carried out using cow dung microflora in a bioreactor. The bioremediation of benzene under the influence of cow dung microflora was found to be 100% and 67.5%, at initial concentrations of 100mg/l and 250 mg/l within 72 h and 168 h respectively; where as at higher concentration (500 mg/l), benzene was found to be inhibitory. Hence the two phase partitioning bioreactor (TPPB) has been designed and developed to carry-out biodegradation at higher concentration. In TPPB 5000 mg/l benzene was biodegraded up to 50.17% over a period of 168 h. Further the Pseudomonas putida MHF 7109 was isolated from cow dung microflora as potential benzene degrader and its ability to degrade benzene at various concentrations was evaluated. The data indicates 100%, 81% and 65% degradation at the concentrations of 50mg/l, 100mg/l, 250 mg/l within the time period of 24h, 96 h and 168 h respectively. The GC-MS data also shows the presence of catechol and 2-hydroxymuconic semialdehyde, which confirms the established pathway of benzene biodegradation. The present research proves the potential of cow dung microflora as a source of biomass for benzene biodegradation in TPPB.

Rhizosphere remediation of chlorpyrifos in mycorrhizospheric soil using ryegrass.

The potential of ryegrass for rhizosphere bioremediation of chlorpyrifos in mycorrhizal soil was investigated by the green house pot culture experiments. The pot cultured soil amended at initial chlorpyrifos concentration of 10mg/kg was observed to be degraded completely within 7 days where the rest amended concentrations (25-100mg/kg) decreased rapidly under the influence of ryegrass mycorrhizosphere as the incubation progressed till 28 days. This bioremediation of chlorpyrifos in soil is attributed to the microorganisms associated with the roots in the ryegrass rhizosphere, therefore the microorganisms surviving in the rhizospheric soil spiked at highest concentration (100mg/kg) was assessed and used for isolation of chlorpyrifos degrading microorganisms. The potential degrader identified by 16s rDNA analysis using BLAST technique was Pseudomonas nitroreducens PS-2. Further, bioaugmentation for the enhanced chlorpyrifos biodegradation was performed using PS-2 as an inoculum in the experimental set up similar to the earlier. The heterotrophic bacteria and fungi were also enumerated from the inoculated and non-inoculated rhizospheric soils. In bioaugmentation experiments, the percentage dissipation of chlorpyrifos was 100% in the inoculated rhizospheric soil as compared to 76.24, 90.36 and 90.80% in the non-inoculated soil for initial concentrations of 25, 50 and 100mg/kg at the 14th, 21st and 28th day intervals respectively.

Bioremediation of phenol by a novel partitioning bioreactor using cow dung microbial consortia.

A bioreactor has been designed and developed for partitioning of aqueous and organic phases with a provision for aeration and stirring, a cooling system and a sampling port. The potential of a cow dung microbial consortium has been assessed for bioremediation of phenol in a single-phase bioreactor and a two-phase partitioning bioreactor. The advantages of the two-phase partitioning bioreactor are discussed. The Pseudomonas putida IFO 14671 has been isolated, cultured and identified from the cow dung microbial consortium as a high-potential phenol degrader. The methods developed in this study present an advance in bioremediation techniques for the biodegradation of organic compounds such as phenol using a bioreactor. We have also demonstrated the potential of microorganisms from cow dung as a source of biomass.

Occupational exposure to dust in quartz manufacturing industry.

Owing to the abundance of a sedimentary rock, 65 small-scale quartz manufacturing enterprises, employing 650 workers, have been established in the region studied. Quartz powder manufacturing involves various processes and operations, such as manual handling of quartz stones, crushing, grinding, sieving, screening, mixing, storing and bagging. Results demonstrate that each of these operations generates high concentrations of airborne 'total' dust and respirable dust, which contain a very high percentage (> 75%) free silica. The estimated average exposure to airborne 'total' dust was 22.5 mg m-3 (Permissible Limit of Exposure 1.08 mg m-3), and respirable dust 2.93 mg m-3 (PLE 0.36 mg m-3). This shows that 'total' dust exposure was 7.7 times higher than respirable dust. Since the present work systems and practices may pose a serious health risk to the workers, public and the environment, suitable preventive and control measures have been suggested for improvement in the workplace.

Occupational exposure to dust in slate pencil manufacture.

Slate pencils are manufactured from natural rock known as Binota Shale in small factories. Since the dust generated by stone-cutting and groove-making machines during the process contains a very high percentage of free silica and the particles are of sizes ranging up to a few microns in diameter the exposure both to respirable and to total inhalable airborne dust was assessed. Dust sizing revealed that all of the dust was respirable (less than 2.5 microns). Measurement of the intake velocity of the exhaust system in many cases showed it to be less than 10 m s-1. Suggestions are made for improvement in the working conditions.