BACKGROUND: The recalcitrant nature of lead (Pb) and mercury (Hg) to degradation represents a real risk to living creatures and their surrounding ecosystems. Therefore, this study employed ureolytic fungal strain Metschnikowia pulcherrima (29A) and bacterial strain Raoultella planticola (VIP) in their removal using the promising CaCO 3 bioprecipitation technique, for the first time.RESULTS: Out of 50 isolates, strains 29A and VIP were selected based on their highest ureolytic activity, followed by minimum inhibitory concentration assay using 350 ppm of Pb 2+ and Hg 2+ . Throughout 7 days of incubation at 30°C and 150 rpm with 10 8 CFU mL −1 inoculum, the maximum urease activity was 884 and 639 U mL −1 for 29A and VIP at 24 and 30 h of incubation, respectively. Complete removal of Pb 2+ was achieved at 42 h (29A) and 90 h (VIP), while Hg 2+ was totally removed at 60 h (29A) and 102 h (VIP). Remarkable removal of Ca 2+ (>95%) was achieved by the end of the experiments, which would address the hardness problem in water treatment processes. Further, energy-dispersive X-ray analysis (EDX), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the remediated precipitates. EDX profiles showed characteristic peaks of C, O and Ca besides Pb and Hg. SEM illustrated the presence of microbial imprints and calcinated cells in the remediated bioliths. However, XRD confirmed transformation of soluble metals to insoluble forms entrapped in calcite or vaterite lattice.CONCLUSIONS: Such a bioremediation approach ensures the detoxification and sequestration of heavy metals in stable and durable matrices, hindering their leaching from carbonate complex trap to the environment.
Bacterial metal reducers were isolated from water samples collected from harsh condition locations in Egypt. Four selected isolates were identified as Enterococcus thailandicus, Pseudomonas putida, Marinobacter hydrocarbonoclasticus, and P. geniculata for Copper (Cu), Iron (Fe), Cobalt (Co) and Zinc (Zn) Nanoparticles (NPs) production sequentially. Nitrate reductase enzyme was assayed for bacterial isolates which demonstrated that P. putida, and M. hydrocarbonoclasticus have the maximum enzyme production. The produced NPs were characterized by using XRD, TEM, UV–VIS spectroscopy. Magnetic properties for all selected metals NPs were measured using Vibrating Sample Magnetometer (VSM) and demonstrated that FeNPs recorded the highest magnetization value. The antibacterial activity of selected metals NPs was tested against some phytopathogenic bacteria causing the following diseases: soft rot (Pectobacterium carotovorum, Enterobacter cloacae), blackleg (Pectobacterium atrosepticum and Dickeya solani), brown rot (Ralstonia solanacearum), fire blight (Erwinia amylovora) and crown gall (Agrobacterium tumefaciens). All metals NPs showed an antagonistic effect against the tested isolates, particularly, FeNPs showed the highest antibacterial activity followed by CuNPs, and ZnNPs. Due to the small size, high reactivity, and large surface area of biologically synthesized NPs, they are used as a good disinfector, and can be considered as a new and alternative approach to traditional disease management methods.
Objectives: To assess the effects of a 4-week levofloxacin course on PSA in asymptomatic men with elevated prostate-specific antigen (PSA) and on prostate biopsy decision. Methods: Fifty asymptomatic men with elevated PSA (4.0–10.0 ng/dl) were given levofloxacin 500 mg/day for 4 weeks followed by repeat PSA. Prostate biopsy was recommended at the end of the study. We compared pre- and post-treatment PSA as well as PSA changes between prostate cancer cases and non-cancer patients. Results: Mean (±SD) PSA decreased from 6.91 ± 2.13 to 6.05 ± 3.0 ng/dl after antimicrobial treatment (p = 0.025). Twenty-five (56.8%) patients had a post-treatment decrease in PSA, including 20 (45.5%) patients to <4.0 ng/dl and/or >25% of the initial PSA value. The difference in PSA change between prostate cancer and non-cancer patients was not statistically significant (p = 0.104). Conclusions: Levofloxacin resulted in an overall decrease in PSA for asymptomatic men with PSA in the 4–10 ng/dl range. PSA changes, however, were not significantly different between patients with prostate cancer and non-cancer patients. Prostate cancer was detected in 20% of patients with a clinically relevant PSA decline.
Herein, respiratory nitrate reductases (NAR) were utilized in the biosynthesis of zero-valent iron (ZVI) graphene nanocomposite as a simultaneous reducing and capping agent, for the first time, to efficiently adsorb methylene blue (MB) and direct red-81 (DR-81). Under anaerobic conditions, the greenly synthesized graphene was incubated with iron precursor in the presence of crude-NAR enzyme for 48 h to obtain the ZVI graphene composite followed by characterizing this composite using physiochemical analyses. Scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction techniques assured the chemical composition and the interaction between ZVI and graphene. The influences of operating conditions such as contact time, pH and adsorbent dose on the adsorption efficacy were explored in the case of ZVI graphene, graphene and ZVI. ZVI graphene nanocomposite displayed the highest removal efficiency of MB and DR-81 compared to graphene and ZVI-NPs. The removal percentages of DR-81 and MB by ZVI graphene nanocomposites were 88.3 ± 2.66% and 87.6 ± 2.1%, respectively, at pH 7, adsorbent dose 20 mg/50 mL, initial MB or DR-81 concentration of 10 mg/L and shaking speed of 150 rpm. A pseudo first-order model could describe the adsorption kinetics, and the adsorption mechanism was discussed. The promising results of the current study support the potential of the recruitment of ZVI graphene nanocomposites in eliminating various pollutants from industrial effluents on a larger scale. Further, the prepared nanohybrid can be used in other applications such as photocatalysis, Fenton and persulfate activation processes.
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