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    Equilibrium, kinetic, and thermodynamic studies on the biosorption of lead by human metallothionein gene-cloned bacteria as a novel biosorbent
    (Wiley, 2024) Akkurt, Seyma; Uckun, Aysel Alkan; Oguz, Merve; Uckun, Mirac; Kahraman, Huseyin
    Heavy metals are the main pollutants in water and are an important global problem that threatens human health and ecosystems. In recent years, there has been an increasing interest in the use of genetically modified bacteria as an eco-friendly method to solve heavy metal pollution problems. The goal of this study was to generate genetically modified Escherichia coli expressing human metallothioneins (hMT2A and hMT3) and to determine their tolerance, bioaccumulation, and biosorption capacity to lead (Pb2+). Recombinant MT2A and MT3 strains expressing MT were successfully generated. Minimum inhibition concentrations (MIC) of Pb for MT2A and MT3 were found to be 1750 and 2000 mg L-1, respectively. Pb2+ resistance and bioaccumulation capacity of MT3 were higher than MT2A. Therefore, only MT3 biosorbent was used in Pb2+ biosorption, and its efficiency was examined by performing experiments in a batch system. Pb2+ biosorption by MT3 was evaluated in terms of isotherms, kinetics, and thermodynamics. The results showed that Pb biosorption fits to the Langmuir isotherm model and the pseudo-first-order kinetic model, and the reaction is exothermic. The maximum Pb2+ capacity of the biosorbent was 50 mg Pb2+g-1. The potential of MT3 in Pb biosorption was characterized by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) analyses. The desorption study showed that the sorbent had up to 74% recovery and could be effectively used four times. These findings imply that this biosorbent can be applied as a promising, precise, and effective means of removing Pb2+ from contaminated waters.Practitioner Points In this study, the tolerance levels, bioaccumulation, and biosorption capacities of Pb in aqueous solutions were determined for the first time in recombinant MT2A and MT3 strains in which human MT2A and MT3 genes were cloned. The biosorbent of MT3, which was determined to be more effective in Pb bioaccumulation, was synthesized and used in Pb biosorption. The Pb biosorption mechanism of MT3 biosorbent was identified using isotherm modeling, kinetic modeling, and thermodynamic studies. The maximum Pb removal percentage capacity of the biosorbent was 90%, whereas the maximum biosorption capacity was up to 50 mg Pb2+g-1. These results indicated that MT3 biosorbent has a higher Pb biosorption capacity than existing recombinant biosorbents. MT3 biosorbent can be used as a promising and effective biosorbent for removing Pb from wastewater. In this study, genetically modified bacteria were used to remove Pb+2 from water, which is an important global problem. To our knowledge, tolerance levels, bioaccumulation, and biosorption capacities of Pb+2 from aqueous solutions of MT2A and MT3 recombinant strains were determined for the first time in this study. MT3 biosorbent can be used as an effective tool for Pb+2 biosorption from water. image
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    The evaluation of low-cost biosorbents for removal of an azo dye from aqueous solution
    (Wiley-Blackwell, 2012) Kahraman, Sibel; Yalcin, Pelin; Kahraman, Huseyin
    There is a need to develop innovative and alternative technologies that can remove dyes from wastewater. In this study, low-cost and locally available two renewable biosorbents (cotton stalk and apricot seed) were investigated to remove of Astrazone Black from aqueous solution. The effects of various experimental parameters such as dye concentration, adsorbent amount, adsorbent particle size and initial pH were tested, and optimal experimental conditions were examined. The results showed that as the amount of adsorbent was increased, the percentage of dye removal increased accordingly. The ratios of dye sorbed increased as the adsorbent particle size decreased. In addition, antibacterial effect of untreated and treated (decolourized) dye on a soil bacterium, Pseudomonas aeruginosa, was determined. The removal of this dye with agricultural wastes reduced the toxic effect on P.?aeruginosa. This reduction in toxic effect is important both in respect of environmental biotechnology and waste detoxification.
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    Production of methionine ?- lyase in recombinant Citrobacter freundii bearing the hemoglobin gene
    (Korean Society Biochemistry & Molecular Biology, 2011) Kahraman, Huseyin; Aytan, Emel; Kurt, Ash Giray
    The production of antileukemic enzyme methionine gamma-lyase (MGL) in distinctly related bacteria, Citrobacter freundii and in their recombinants expressing the Vitresocilla hemoglobin (VHb) has been studied. This study concerns the potential of Citrobacter freundii expressing the Vitreoscilla hemoglobin gene (vgb) for the methionine gamma- liyase production. Methionine gamma- liyase production by Citrobacter freundii and its vgb(-) and vgb(+) bearing recombinant strain was studied in shake-flasks under 200 rpm agitation, culture medium and 30 degrees C in a time-course manner. The vgb(+) and especially the carbon type had a dramatic effect on methionine gamma- liyase production. The vgb(+) strain of C. freundii had about 2-fold and 3.1-fold higher levels of MGL than the host and vgb(-) strain, respectively. [BMB reports 2011; 44(9): 590-594]
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    Pyocyanine Production, Twitching Motility and Hydrophobicity of Different Wastes on Pseudomonas aeruginosa
    (Hard, 2021) Kahraman, Huseyin; Karaderi, Cennet Canan
    Many agricultural and biological waste materials cause environmental problems. To address this, and to achieve economic efficiency (growth, cell surface hydrophobicity (CSH), twitching, biofilm, and pyocyanin production), we used different organic wastes and Pseudomonas aeruginosa (P. aeruginosa). While there is biofilm formation in all organic waste assets, the highest such formation was observed in molasses and waste cheese whey (WCW). Average pyocyanin production in all organic waste except for Nutrient Broth (NB) averaged 3 mu g/ml. CSH was reached only in the presence of olive waste water (OWW), molasses, and WCW. The highest twitching was achieved by adding WCW at 14 mm. We found no similar studies with P. aeruginosa in the literature. We think that this research will result in similar new studies that will reveal methods of handling these waste materials economically thus benefiting the environment.