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Objectives: To evaluate Pseudomonas monteilii strain PN1 for the removal efficiency of P-nitrophenol (PNP) in soils and its growth promotion of maize (Zea mays L.) seedlings under drought and saline–alkali stress. Results: PN1 can survive in soils contaminated with PNP dosage between 90 and 155 mg/kg and considerably improved the removal PNP efficiency in soils. Drought and saline–alkali stress reduced maize seedling growth (root length, shoot height and dry or fresh weight) and improved the antioxidant enzyme activities and malondialdehyde (MDA) and proline (PRO) contents. However, maize seedlings treated with PN1 remarkably promoted their growth compared with the control. The reduction in antioxidant enzyme activities and MDA and PRO contents was significant. This result may be correlated to the increased tolerance of maize seedlings to drought and saline–alkali stress. Conclusions: Application of P. monteilii PN1 can be an extremely useful approach for the development of bioinoculants in improving plant tolerance to several abiotic stresses and removing PNP in soils to ensure secure crop production. [ABSTRACT FROM AUTHOR]

The success of bioaugmentation processes for the remediation of groundwater contamination relies on effective transport of the injected microorganisms in a subsurface environment. Biosurfactants potentially affect bacterial attachment and transport behavior in porous media. Although saponins as biosurfactants are abundant in nature, their influence on bacterial transport in groundwater systems remains unknown. In this research, tank visual-transport experiments, breakthrough curve monitoring, and surface property measurement were performed to evaluate the effects of saponins on the transport of Pseudomonas migulae AN-1 cells, which were used as a model bacterium in saturated sand. Results show that the 0.1% saponins could effectively facilitated the AN-1 secondary transport and the addition of saponins decreased the hydrophobicity of AN-1 and sand. The role of the promotion of saponins was more dominant than that of the inhibition of ions on AN-1 transport in a saturated porous medium when ions and saponins coexisted. The interactions between AN-1 and sand grains with saponins and ions were explained in accordance with the Derjaguin-Landau-Verwey-Overbeek theory. [ABSTRACT FROM AUTHOR]

Metronidazole (MNZ) is widely used in clinical applications and animal feed as an antibiotic agent and additive, respectively. Widespread occurrence of MNZ in wastewater treatment and hospital effluents has been reported. In this study, the mechanism of MNZ degradation in aqueous solutions via thermally activated persulfate (TAP) process was established under different conditions. The kinetic model was derived for MNZ degradation and followed pseudo-first-order reaction kinetics and was consistent with the model fitted by experimental data ( R > 98.8%). The rate constant increased with the initial dosage of persulfate, as well as the temperature, and the yielding apparent activation energy was 23.9 kcal mol. The pH of the solutions did not have significant effect on MNZ degradation. The degradation efficiency of MNZ reached 96.6% within 180 min for an initial MNZ concentration of 100 mg L under the optional condition of [PS] = 20 mM, T = 60 °C, and unadjusted pH. $$ {SO}_4^{\cdotp -} $$ and HO were confirmed using electron paramagnetic resonance (EPR) spectra during TAP process. Radical quenching study revealed that $$ {SO}_4^{\cdotp -} $$ was mainly responsible for MNZ degradation at an unadjusted pH. MNZ mineralization evaluation showed that the removal efficiency of total organic carbon (TOC) reached more than 97.2%. [ABSTRACT FROM AUTHOR]

Objective: To investigate the remediation efficiency of polychlorinated biphenyl (PCB)-contaminated soils by the combination of a bioemulsifying protein, AlnA, and alfalfa expressing bphC. Result: The combination of AlnA and transgenic alfalfa promoted PCB soil remediation through the pot experiments. The removal rates of tri-PCBs (PCB 16/PCB 32 and PCB 31/PCB 28) and tetra-PCB (PCB 49) in transgenic alfalfa/AlnA treatment were 3.6-, 1.1-, and 2-fold higher than in transgenic alfalfa treatment alone. Analysis of gene copy number revealed that the PCB-degrading gene, bphC, of Pseudomonas-like bacterial populations in transgenic alfalfa/AlnA treatment increased 1.5-fold compared with that of unplanted soils. Bacterial community Illumina sequencing showed Pseudomonas, Arthrobacter, and Sphingomonas positively correlated with the removal rates of PCBs. Conclusions: PCB removal was unrelated to bacterial community diversity but positively correlated with their specific degraders and bphC gene expression. [ABSTRACT FROM AUTHOR]

The formation and activity of aniline-degrading biofilms developed by the psychrotrophic Pseudomonas migulae AN-1 were studied for the in situ remediation of contaminated aquifer using in-well bioreactor of groundwater circulating wells (GCWs). Biofilms grown in mineral salt medium with aniline exhibited tolerance to high concentrations of aniline. In aniline degradation rate, AN-1 biofilms exhibited slight differences compared with planktonic cells. The effectiveness and bio-implication of AN-1 biofilms in GCWs were investigated to treat aniline-contaminated aquifer. The results demonstrate that AN-1 biofilms survived the GCWs treatment process with high aniline-degrading efficiency. This system provides a novel environmentally friendly technology for the in situ bioremediation of low-volatile contaminants. [ABSTRACT FROM AUTHOR]

The migration and distribution of contaminants in heterogeneous aquifers are mostly investigated through numerical simulations. They are rarely examined through experimental simulations because of sampling difficulties. In this study, we used the light transmission method (LTM) to explore the migration and distribution of hexavalent chromium [Cr(VI)] in homogeneous sandy aquifers with or without a low-permeability bottom and lens (heterogeneous aquifer). Experimental phenomena were observed via images obtained with a high-power light source. The migration distances of pollution plume were also monitored. Under heterogeneous conditions, low-permeability aquifer materials considerably inhibited the migration of Cr(VI) and altered the Cr(VI) migration rate of horizontal and vertical plumes spread to a certain extent. Common horizontal and vertical migration curve equations in all three conditions were also obtained through distance-time curve fitting. The difference between high- and low-concentration zones was accurately revealed, and the experimental phenomenon was further explained. The proposed method could be used for the qualitative investigation and visualization of the migration and distribution of Cr(VI). [ABSTRACT FROM AUTHOR]