Anita Rajor

Calcium carbonate precipitation by different bacterial strains

Bacteria are capable of performing metabolic activities which thereby promote precipitation of calcium carbonate in the form of calcite. In this study, it is shown that microbial mineral precipitation was a result of metabolic activities of some specific microorganisms. Concrete microorganisms were used to improve the overall behavior of concrete. It was predicted that bacterial calcium carbonate (CaCO 3) precipitation occurs as a byproduct of common metabolic processes such as urea hydrolysis. In this study, ureolytic bacteria that were capable of precipitating calcium carbonate were isolated and further their urease activity was tested based on the production of urease. Scanning electron microscopy (SED) analysis revealed the direct involvement of these isolates in calcium carbonate precipitation. The production of calcite was further confirmed by x-ray diffraction (XRD) and energy-dispersive x-ray (EDX) analysis.

An overview on characterization, utilization and leachate analysis of biomedical waste incinerator ash

Solid waste management is one of the major global environmental issues, as there is continuous increase in industrial globalization and generation of waste. Solid wastes encompass the heterogeneous mass of throwaways from the urban community as well as the homogeneous accumulations of agricultural, industrial and mineral wastes. Biomedical waste pose a significant impact on health and environment. A proper waste management system should be required to dispose hazardous biomedical waste and incineration should be the best available technology to reduce the volume of this hazardous waste. The incineration process destroys pathogens and reduces the waste volume and weight but leaves a solid material called biomedical waste ash as residue which increases the levels of heavy metals, inorganic salts and organic compounds in the environment. Disposal of biomedical waste ash in landfill may cause contamination of groundwater as metals are not destroyed during incineration. The limited space and the high cost for land disposal led to the development of recycling technologies and the reuse of ash in different systems. In order to minimize leaching of its hazardous components into the environment several studies confirmed the successful utilization of biomedical waste ash in agriculture and construction sector. This paper presents the overview on the beneficial use of ash in agriculture and construction materials and its leachate characteristics. This review also stressed on the need to further evaluate the leachate studies of the ashes and slag for their proper disposal and utilization.

Degradation of Imidacloprid in Liquid by Enterobacter sp. Strain ATA1 Using Co-Metabolism

ABSTRACT Imidacloprid (IMI), a potent insecticide, belongs to the neonicotinoid family and is of great concern due to the fact that its persistence in the soil is a threat to both plants and vertebrates. The present study was aimed at the isolation and characterization of a bacterial strain from paddy field soil at Punjab (India), which has a history of 9–10 years of imidacloprid contamination. Among the various isolates, a soil bacterium was selected and identified by 16S rRNA gene sequencing as Enterobacter sp. strain ATA1. It grew well in pH ranging from 6.0 to 7.0 at 37°C, and it was found to be a competent bacterium for the degradation of IMI. The presence of glucose in minimal salt medium (MMG; 0.1% w/v) as compared with any other co-substrate provokes the dissipation of IMI as a co-metabolite. Initially, incubation of IMI for 72 h in the MMG resulted in 30–40% degradation; thereafter, no significant change in its amount was found until 15 days of incubation, which explains the disappearance of any viable cells in the medium. Among the various identified metabolites, imidacloprid urea (m/z = 212) and imidacloprid guanidine (m/z = 211) were found to be the end products of IMI degradation, whereas others remained unidentified (m/z = 99 and m/z = 119).

Photocatalytic degradation of imidacloprid in soil: application of response surface methodology for the optimization of parameters

The photocatalytic mineralization of imidacloprid (IMI) in soil to inorganic ions and the formation of various intermediates using TiO2 as the photocatalyst have been investigated under UV light. Various parameters, viz., catalyst concentration, soil depth and pH, intensity of light and initial concentration of IMI were optimized theoretically by using a central composite design based on a response surface methodology and were correlated with experimental results. The statistical analysis from the modelling results indicates that the degradation efficiency of IMI is affected by the depth of soil and the intensity of light, but the effects of the pH and the initial concentration of imidacloprid are more dominant. The optimum conditions obtained for the maximum degradation of imidacloprid were at pH = 3, intensity of UV light = 30 W m−2, soil depth = 0.2 cm and initial concentration of imidacloprid = 10 mg kg−1 of soil. Under these optimum conditions, the highest degradation efficiency of 83% was achieved after 18 h of UV light irradiation. The identification of various photoproduced intermediates of IMI by LC-MS analysis revealed its degradation, whereas the increase in the formation of inorganic ions with time of UV light irradiation confirms its mineralization.

Identification of the potential of microbial combinations obtained from spent mushroom cultivation substrates for use in textile effluent decolorization

The study presents variation in microbial population of Agaricus bisporus, Pleurotus sajor-caju and Volvariella volvacea spent substrates (SMS) along with ligninolytic enzymes activity and textile effluent decolorization potential of microorganisms isolated from these. The effect of temperature, pH, carbon sources and immobilizing agents on effluent decolorization using different combinations of these microorganisms has also been studied. SMS of P. sajor-caju harbored highest population and diversity of bacteria and fungi compared to other SMSs. Schizophyllum commune and Pezizomycotina sp. from P. sajor-caju SMS, exhibited highest activities of laccase (11.8 and 8.32U mL(-1)) and lignin peroxidase (339 and 318 UL(-1)), while Pseudomonas fluorescens of Manganese peroxidase. Highest decolorization was in presence of glucose and sucrose at 30°C, and microbial consortium comprised of the immobilized forms of S. commune and Pezizomycotina sp. on wheat straw and broth cultures of P. fluorescens, Bacillus licheniformis and Bacillus pumilus.

Bacterial treatment of alkaline cement kiln dust using Bacillus halodurans strain KG1

This study was conducted to isolate an acid-producing, alkaliphilic bacterium to reduce the alkalinity of cement industry waste (cement kiln dust). Gram-positive isolate KG1 grew well at pH values of 6–12, temperatures of 28–50 °C, and NaCl concentrations of 0–16% and thus was further screened for its potential to reduce the pH of an alkaline medium. Phenotypic characteristics of the KG1 isolate were consistent with those of the genus Bacillus, and the highest level of 16S rRNA gene sequence similarity was found with Bacillus halodurans strain DSM 497 (94.7%). On the basis of its phenotypic characteristics and genotypic distinctiveness from other phylogenetic neighbors belonging to alkaliphilic Bacillus species, the isolated strain was designated B. halodurans strain KG1, with GenBank accession number JQ307184 (= NCIM 5439). Isolate KG1 reduced the alkalinity (by 83.64%) and the chloride content (by 86.96%) of cement kiln dust and showed a potential to be used in the cement industry for a variety of applications.

Isolation, Characterisation of Novel Pseudomonas and Enterobacter sp. from Contaminated Soil of Chandigarh for Naphthalene Degradation

Naphthalene an organic pollutant arises from industrial operations and natural events such as forest fires. According to US EPA list of priority pollutants, naphthalene is considered as possible carcinogen due to its low solubility and bioavailability. Degradation of this recalcitrant can be carried out using physical and chemical methods but it leads to various products, most of them are toxic to the environment. Therefore, bioremediation using selected microorganisms remains the most suitable solution to treat such pollutants.