Ludwigia stolonifera for remediation of toxic metals from simulated wastewater

The present study investigated the phytoremediation of simulated wastewater, mimicking wastewater generated by industrial processes containing significant amounts of toxic heavy metal ions. The wetland plant Ludwigia stolonifera was used to study its efficiency in the removal of the three toxic metals Pb, Cd and Cr. Survivability of the plant has been studied in solutions at different concentrations of three metals separately or as a mixture, and the accumulation of these toxic metals for a prolonged period has been evaluated. The plant performed very successful in eliminating Cd, Cr and Pb as single metals of up to 65%, 97% and 99%, respectively, within four days. In addition, the trend of metal uptake revealed negligible dependence on different masses of plant and on various pH-values. L. stolonifera has high potential in eliminating various toxic pollutants from aquatic environments.     

The potential of different bio adsorbents for removing phenol from its aqueous solution

The use of natural resources for the removal of phenol and phenolic compounds is being looked upon by researchers in preference to other prevailing methods. In the present study, different biosorbents, brown algae (Padina pavonia), fresh water macrophyta (Ceratophyllum demersum), and black tea residue, were tested as adsorbent for the removal of phenol from aqueous solutions. The optimum conditions for maximum adsorption in terms of concentration of the adsorbate and pH were identified. The results show that the initial concentration increases as the removal of phenol increases in C. demersum; in the case of the other two adsorbents, the initial concentration increases as the removal of phenol decreases, especially for an initial concentration lower than 100 and 1,000 μg/L for P. pavonia and black tea residue, respectively. Maximum percentage removal of phenol by each adsorbent is 77, 50.8, and 29 % for C. demersum, P. pavonia, and black tea residue, respectively. Also, the biosorption capacity was strongly influenced by the pH of the aqueous solution with an observed maximum phenol removal at pH of around 6–10. The first biosorbent (black tea residue) displays the maximum adsorption capacity at a pH of 10 with a percentage sorption capacity of 84 %; P. pavonia revealed a greater adsorption percentage at pH?10, reaching 30 %, while for C. demersum, the removal of phenol increases with the increase in initial pH up to 6.0 and decreases drastically with further increase in initial pH. The Freundlich, Langmuir, and Brauner–Emmet–Teller adsorption models were applied to describe the equilibrium isotherms. The results reveal that the equilibrium data for all phenol adsorbents fitted the Freundlich model which seemed to be the best-fitting model for the experimental results with similar values of coefficient of determination.     

3D-QSAR of fungal quorum-sensing inhibiting analogs of farnesol

Thirty-four analogs with variable antifungal activity were selected to develop models for establishing three-dimensional quantitative structure-activity relationships (3D-QSAR). Comparative molecular field analysis (CoMFA) and comparative similarity indices analyses (CoMSIA) were conducted on the group of analogs to determine the structural requirements for selectivity and potency in inhibiting biofilm formation and fungal growth. The best CoMFA model predicted a q² = 0.5 and an r² = 0.991, and revealed that electrostatic properties play a significant role in potency and selectivity. The best CoMSIA model combined electrostatics, hydrogen bond acceptor and donor, and hydrophobic fields with a q² = 0.664 r² = 0.952, S = 0.099, and F = 139.892. The analyses of the contour maps from both models provide significant insight into the structural necessities for a potent compound. Therefore, manipulating various chemical properties of the substituted groups on the farnesol chain can be used to enhance the fungicidal properties of the target compound.     

Three-dimensional quantitative structure activity relationships of quorum-sensing and biofilm inhibitors in gram-negative bacteria

Thirty N-acyl homoserine lactone (AHL) analogs with variable antibacterial activity and displaying inhibition of biofilm formation were selected to develop models for establishing three-dimensional quantitative structure-activity relationships (3D-QSAR). Comparative molecular field analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were carried out to determine the optimum structural requirements for selectivity and potency of quorum-sensing and bacterial biofilm inhibition. The best CoMFA model predicted a q² value of 0.519 and an r² value of 0.984 and revealed that electrostatic and steric properties play a significant role in potency and selectivity. The CoMSIA model predicted a q² value of 0.411 and an r² value of 0.938 based on a combination of steric, electrostatic, and hydrophobic effects. The analysis of the contour maps from each model provide insight into the structural requirements for increasing the activity of a compound. Consequently, manipulating the chemical and physical properties of substituted acyl groups on the homoserine lactone moiety can provide important information toward enhancing the antibacterial properties of the target chemical compound.     

Three-dimensional quantitative structure activity relationships of quorum-sensing and biofilm inhibitors in gram-negative bacteria

Thirty N-acyl homoserine lactone (AHL) analogs with variable antibacterial activity and displaying inhibition of biofilm formation were selected to develop models for establishing three-dimensional quantitative structure-activity relationships (3D-QSAR). Comparative molecular field analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were carried out to determine the optimum structural requirements for selectivity and potency of quorum-sensing and bacterial biofilm inhibition. The best CoMFA model predicted a q2 value of 0.519 and an r2 value of 0.984 and revealed that electrostatic and steric properties play a significant role in potency and selectivity. The CoMSIA model predicted a q2 value of 0.411 and an r2 value of 0.938 based on a combination of steric, electrostatic, and hydrophobic effects. The analysis of the contour maps from each model provide insight into the structural requirements for increasing the activity of a compound. Consequently, manipulating the chemical and physical properties of substituted acyl groups on the homoserine lactone moiety can provide important information toward enhancing the antibacterial properties of the target chemical compound.     

Tolerance of transgenic canola plants (Brassica napus) amended with plant growth-promoting bacteria to flooding stress at a metal-contaminated field site

The growth of transgenic canola (Brassica napus) expressing a gene for the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase was compared to non-transformed canola exposed to flooding and elevated soil Ni concentration, in situ. In addition, the ability of the plant growth-promoting bacterium Pseudomonas putida UW4, which also expresses ACC deaminase, to facilitate the growth of non-transformed and transgenic canola under the above mentioned conditions was examined. Transgenic canola and/or canola treated with P. putida UW4 had greater shoot biomass compared to non-transformed canola under low flood-stress conditions. Under high flood-stress conditions, shoot biomass was reduced and Ni accumulation was increased in all instances relative to low flood-stress conditions. This is the first field study to document the increase in plant tolerance utilizing transgenic plants and plant growth-promoting bacteria exposed to multiple stressors.     

Chemical composition and antimicrobial activities of the essential oil from the seeds of Enterolobium contortisiliquum (leguminosae)

Seeds of Enterolobium contortisiliquum were subjected to steam distillation to obtain a light yellow essential oil in a yield of 3 ml/kg of seeds. The major components of the oil were identified using gas chromatography/mass spectrometry (GC-MS) and were furfural, limonene, linalool, estragole, carvone, and apiole with carvone representing more than 50% of the total composition. Antimicrobial activities of the essential oil were determined against four species of gram positive bacteria (Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Micrococcus luteus) and two gram negative bacteria (Klebsiella pneumoniae, Serratia Marcescencs). The essential oil inhibited the growth of all tested bacteria but was most effective against the gram positive bacteria. Chemicals that are responsible for the antibacterial effect of the essential oil were determined using the bio-autography thin layer chromatography (TLC) technique. The active compounds responsible for the activity were found to be carvone and estragole.     

Nematicidal activity of terpenoids

Thirty four phytoterpenoids were evaluated for their nematicidal effect using the model nematode Caenorhabditis elegans. Nematicidal activities of the tested compounds at concentrations of 50 μg/mL showed wide variation in their effects ranging from no effect, weak, moderate and strong effects. Terpenoids exerting 50% or higher mortality at 50 μg/mL were further tested at five different concentrations to calculate the concentration that will kill 50% of the nematode population (LC₅₀). Among the most effective terpenoids were carvacrol, thymol, nerolidol, α-terpinene, geraniol, citronellol, farnesol, limonene, pseudoionone and eugenol in a descending order. These compounds exhibited a dose-dependent effect. The results suggest that the selected monoterpenoids and essential oils with a high concentration of these compounds mayprovide potential natural nematicides and merit further study as botanical nematicides for the control of both plant and animal parasitic nematodes. In general, oxygenated terpenoids and phenolic terpenoids exhibited higher nematicidal activity than hydrocarbons terpenoids.     

Flow photocatalysis system-based functionalized graphene oxide-ZnO nanoflowers for degradation of a natural humic acid

Environmental Science and Pollution Research - The functionalized graphene oxide-ZnO (fGO/ZnO) nanoflower composites have been studied as a photocatalyst material for flow photodegradation of humic...     

Safety in the mining industry and the unfinished legacy of mining accidents: Safety levers and defense-in-depth for addressing mining hazards

Mining remains one of the most hazardous occupations worldwide and underground coal mines are especially notorious for their high accident rates. In this work, we provide an overview of the broad and multi-faceted topic of safety in the mining industry. After reviewing some statistics of mining accidents in the United States, we focus on one pervasive and deadly failure mode in mines, namely explosions. The repeated occurrence of mine explosions, often in similar manner, is the loud unfinished legacy of mining accidents and their occurrence in the 21st century is inexcusable and should constitute a strong call for action for all stakeholders in this industry to settle this problem. We analyze one such recent mine disaster in which deficiencies in various safety barriers failed to prevent the accident initiating event from occurring, then subsequent lines of defense failed to block this accident scenario from unfolding and to mitigate its consequences. We identify the technical, organizational, and regulatory deficiencies that failed to prevent the escalation of the mine hazards into an accident, and the accident into a “disaster”. This case study provides an opportunity to illustrate several concepts that help describe the phenomenology of accidents, such as initiating events, precursor or lead indicator, and accident pathogen. Next, we introduce the safety principle of defense-in-depth, which is the basis for regulations and risk-informed decisions by the US Nuclear Regulatory Commission, and we examine its relevance and applicability to the mining system in support of accident prevention and coordinating actions on all the safety levers, technical, organizational, and regulatory to improve mining safety. The mining system includes the physical confines and characteristics of the mine, the equipment in the mine, the individuals and the organization that operate the mine, as well as the processes and regulatory constraints under which the mine operates. We conclude this article with the proposition for the establishment of defense-in-depth as the guiding safety principle for the mining industry and we indicate possible benefits for adopting this structured hazard-centric system approach to mining safety.