Screening, identification and experimental design to optimization of the selenite bioremediation by new isolated Bacillus sp. Selena 3 in water.

Background and Objectives: Heavy metals pollution is one of the most important concerns in the world. Selenium is one of the most important elements for the life, but if the absorption of this element in cells increases, it acts as a toxic element. Materials and Methods: In this study, bacterial isolates were screened and isolated from selenium-contaminated soil and water. Twenty-five out of 42 isolates were able to reduce Selenite. Also, the response surface method (RSM) was used to evaluate and optimize the biological reduction of selenite by Selena 3. Factors of bacterial inoculation percentage, time, and amount of selenium oxyanion salt concentration were studied at five levels of -α, -1, 0, +1, and +α. Results: Bacillus sp. Selena 3 was able to reduce 80 mM sodium selenite in less than 4 hours compared to other bacterial isolates. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of sodium selenite Bacillus sp. Selena 3 was reported as 160 and 320 mM, respectively. The results showed that with increasing duration, the percentage of selenite reduction by bacteria increases and the percentage of bacterial inoculation does not have much effect on its reduction. Conclusion: Due to the ability of Bacillus sp. Selena 3 for rapid reduction in significant concentration of selenium oxyanion (SeO32-), this bacterium can be used as an efficient candidate in removing selenite from the environment.

A Biotechnological Strategy for Molybdenum Extraction Using Acidithiobacillus ferrooxidans.

Biosorption is a potential tool for the extraction of metals from contaminated water and recovery of precious metals, which is a convenient alternative to conventional processes. In the present study, molybdenum recovery by Acidithiobacillus ferrooxidans strain ZT-94 was evaluated. Additionally, the effects of pH initial concentration of molybdenum, contact time, adsorbent concentration, and temperature on the biosorption were investigated. As revealed by the results, the greatest amount of molybdenum sorption was achieved at pH 5. By increasing the concentration of molybdenum from 2 to 45 mg/l, the molybdenum removal increases from 71.13 to 150 mg/g dry weight of biomass, but biosorption efficiency decreased. Also, increasing the dry weight of biomass from 0.008 to 0.06 g/l degreased the biosorption efficiency from 20.68 to 85.69%. The results of molybdenum biosorption were evaluated by Langmuir and Freundlich adsorption isotherm. The maximum biosorption capacity for molybdenum extraction was 150.497 mg/g and amount which is very suitable for a biosorbent. The biosorption was examined by scanning electron microscopy-energy-dispersive X-ray spectroscopy. Because of the elevated biosorption properties of molybdenum by this biosorbent, it can be concluded that Acidithiobacillus ferrooxidans strain ZT-94 is a promising candidate for the removal and recovery of molybdenum from aqueous systems.

Radiolabeling of Biogenic Magnetic Nanoparticles with Rhenium-188 as a Novel Agent for Targeted Radiotherapy.

Use of nanoparticles as carriers of anticancer drugs is a suitable way for targeted drug delivery and reduction of the side effects. This research focuses on a novel drug carrier for therapeutic goals by the bacterial magnetic nanoparticles (magnetosomes). The unique characteristics of magnetosomes make them ideal nanobiotechnological materials. In this study, magnetic nanoparticles of Alphaproteobacterium MTB-KTN90 were labeled with the radioisotope rhenium-188 and optimized the factors affecting the labeling efficiency. The results showed that the labeling efficiency of magnetosomes with rhenium-188 was more than 96%. The optimum concentration of bacterial nanoparticles was 133 mg/ml and the best time for maximum efficiency labeling was 60 min. The labeling stability showed that the 188Re-nanoparticle complexes have good stability in 29 h. The results of magnetic nanoparticles bacterial cytotoxicity on cancer cells AsPC1 did not show significant toxicity to concentration of 100 µg/µl. Finally, the biogenic magnetic nanoparticles labeled with rhenium-188 can be introduced as a valuable candidate for the targeted therapy of tumor with reducing radiation to surrounding healthy tissues.

Cobalt separation by Alphaproteobacterium MTB-KTN90: magnetotactic bacteria in bioremediation.

Bioremediation of toxic metals by magnetotactic bacteria and magnetic separation of metal-loaded magnetotactic bacteria are of great interest. This bioprocess technique is rapid, efficient, economical, and environmentally friendly. In this study, cobalt removal potential of a novel isolated magnetotactic bacterium (Alphaproteobacterium MTB-KTN90) as a new biosorbent was investigated. The effects of various environmental parameters in the cobalt removal and the technique of magnetic separation of cobalt-loaded bacterial cells were studied. Cobalt removal by MTB-KTN90 was very sensitive to pH solution; higher biosorption capacity was observed around pH 6.5-7.0. When biomass concentration increased from 0.009 to 0.09 g/l, the biosorption efficiency increased from 13.87 % to 19.22 %. The sorption of cobalt by MTB-KTN90 was rapid during the first 15 min (859.17 mg/g dry weight). With the increasing of cobalt concentrations from 1 to 225 mg/l, the specific cobalt uptake increased. Maximum cobalt removal (1160.51 ± 15.42 mg/g dry weight) took place at optimum conditions; pH 7.0 with initial cobalt concentration of 115 mg/l at 60 min by 0.015 g/l of dry biomass. The results showed maximum values for constants of Langmuir and Freundlich models so far. The biosorption mechanisms were studied with FTIR, PIXE, and FESEM analysis. Cobalt-loaded MTB-KTN90 had ability to separate from solution by a simple magnetic separator. Magnetic response in MTB-KTN90 is due to the presence of unique intracellular magnetic nanoparticles (magnetosomes). The orientation magnetic separation results indicated that 88.55 % of cobalt was removed from solution. Consequently, Alphaproteobacterium MTB-KTN90 as a new biosorbent opens up good opportunities for the magnetic removal of cobalt from the polluted aquatic environments.

Isolation and Characterization of a Novel Magnetotactic Bacterium From Iran: Iron Uptake and Producing Magnetic Nanoparticles in Alphaproteobacterium MTB-KTN90.

BACKGROUND: Magnetotactic bacteria (MTB) have the ability to biomineralize unique intracellular magnetic nanosize particles. These bacteria and their magnetosomes are under special attraction because of their great useful potential in nano-biotechnological and biomedical applications. MTB are ubiquitous in aquatic environments, but their isolation and axenic cultivation in pure culture is very difficult and only a limited number of them have been isolated in pure culture. OBJECTIVES: The main goal of this study was screening, isolation and cultivation of a new strain of these fastidious bacteria in pure culture from Iran to use them and their magnetosomes. MATERIALS AND METHODS: Thirty samples were collected from various aquatic habitats. Most important physicochemical environmental factors that are involved in growth of MTB in the microcosms were investigated using inductively coupled plasma atomic emission spectroscopy (ICP-AES), portable dissolved oxygen meter, etc. Capillary racetrack technique and magnetic separation were used to purify and enrich MTB. Various isolation media were simultaneously used for isolation of a new magnetotactic bacterium in pure culture. Two imaging techniques were used to visualize the characterizations and cell division: transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FESEM). Polymerase chain reaction (PCR), ChromasPro software and MEGA5 were applied for sequence analysis of the 16S rRNA gene. RESULTS: The results revealed a correlation of important physicochemical factors such as pH and iron with growth and blooms of these bacteria in the microcosms. New strain MTB-KTN90 was isolated in a modified isolation medium at microaerophilic zone from Anzali lagoon, Iran and cultured in a modified growth medium subsequently. The phylogenetic analysis showed that the strain belongs to Alphaproteobacteria. Growth and iron uptake studies indicated an important role by this bacterium in the iron biogeochemical cycle. For the first time, this paper introduced a cultured magnetotactic Alphaproteobacterium, able to synthesize magnetosomes in the temperatures above 30°C and reduce selenate oxyanion. CONCLUSIONS: This paper may serve as a guide to screening, isolation, and cultivation of more new MTB. The new isolated strain opens up good opportunities for biotechnological applications such as medicine to bioremediation processes due to its unique abilities.

Effect of salinity on vanadate biosorption by Halomonas sp. GT-83: preliminary investigation on biosorption by micro-PIXE technique.

Thirty-eight soil samples were collected from crude oil contaminated land in south of Iran. Initial screening of a total of 100 bacterial isolates, resulted in the selection of one isolate with maximum adsorption capacity of 52.7 mg vanadate/g dry weight. It was tentatively identified as Halomonas sp. according to morphological and biochemical properties and named strain GT-83. Removal of vanadate by biosorption with Halomonas sp. GT-83 was very sensitive to solution pH. Vanadate adsorption decreased with increasing pH, with maximum adsorption capacities achieved in at pH 3.0 in the absence and in the presence of increasing concentrations of salt. Vanadate-salt biosorption studies were also performed at this pH value. Equilibrium uptakes of vanadate increased with increasing vanadate concentration up to 600 mg/l. Maximum metal removal (91.8%) took place at pH 3.0 with initial vanadate concentration of 100mg/l, which got reduced (84.8%) in the presence of 50 g/l salt. The equilibrium sorption data were analyzed by using Freundlich isotherm. The specific uptake of vanadate increased at low cell concentration and decreased when cell concentration exceeded 0.75 g/l. The paper also demonstrates the potential value of micro-PIXE in biosorption studies.

Uptake of Re(VII) from aqueous solutions by Bacillus sp. GT-83-23.

Thirty-eight water samples were collected from various areas of Anzali lagoon, Iran. Initial screening of a total of 100 bacterial isolates, resulted in the selection of one isolate with maximum adsorption capacity. It was tentatively identified as Bacillus sp. and named strain GT-83-23. The optimum pH of the medium was found to be 2.0 for Re(VII) adsorption. Uptakes of Re(VII) increased with increasing Re(VII) concentration and decreased sharply by the presence of increasing concentrations of NaCl. The kinetic of Re(VII) sorption by Bacillus sp. GT-83-23 was fast, reaching more than 62% of the total sorption capacity within 5 min. As the cell concentration increased, the amount of Re(VII) adsorbed by each cell (specific uptake) decreased, whereas the total amount of Re(VII) adsorbed enhanced. Cells immobilized in calcium alginate gel took up 77% of the Re(VII). The binding of Re(VII) on the Bacillus sp. GT-83-23 was studied with micro-PIXE.

Biotechnological potential of Azolla filiculoides for biosorption of Cs and Sr: Application of micro-PIXE for measurement of biosorption.

The presence of Cs and Sr in culture medium of Azolla filiculoides caused about 27.4% and 46.3% inhibition of biomass growth, respectively, in comparison to A. filiculoides control weight which had not metals. Biosorption batch experiments were conducted to determine the Cs and Sr binding ability of native biomass and chemically modified biosorbents derived from Azolla namely ferrocyanide Azolla sorbents type 1 and type 2 (FAS1 and FAS2) and hydrogen peroxide Azolla sorbent (HAS). The best Cs and Sr removal results were obtained when A. filiculoides was treated by 2M MgCl(2) and 30ml H(2)O(2) 8mM at pH 7 for 12h and it was then washed by NaOH solution at pH 10.5 for 6h. Pretreatment of Azolla have been suggested to modify the surface characteristics which could improve biosorption process. The binding of Cs and Sr on the cell wall of Azolla was studied with micro-PIXE and FT-IR.