본 연구에서는 세포 표면 발현 시스템을 이용한 미생물 흡착 공정을 이용하였다. 재조합 균주를 이용하여 금속흡착 후 열분해로 생성된 나노입자와 금속흡착 후 회복을 위한 다양한 처리방법을 이용하여 항생제로서의 역할을 확인하는 실험을 진행하였다. 흡착 및 탈착된 아연의 정량분석은 ICP-OES를 이용하여 수행하였다.
또한, 실험에서 얻은 데이터를 검증하는 과정은 Langmuir 및 Freundlich 흡착 등온선을 이용한다. OmpC zraP 도입 균주에 Zinc를 적용하여 흡착시켰으며, 사용되는 탈착 방법은 물리적 방법과 화학적 방법으로 구분하였다. 통상적으로 미생물에 흡착된 금속을 탈착하기 위해 화학적 방법인 EDTA를 이용하지만, 본 연구에서는 물리적인 방법으로도 금속을 탈착할 수 있는지 여부를 확인하였다.
또한 미생물에 흡착된 금속이온을 열분해하여 아연나노입자를 형성하고 이를 대장균 배양액에 투여하고 매시간 성장속도를 측정하여 아연나노입자가 항생물질로 작용하는지 확인하였다. E의 성장속도를 확인하였다. 대장균은 배양 배지에서 아연 나노 입자의 양이 증가함에 따라 감소했습니다. E의 성장속도를 확인하였다. 대장균은 배양 배지에서 아연 나노 입자의 양이 증가함에 따라 감소했습니다.
-SEM images of the recombinant E. Effect of adsorption pH on zinc biosorption in 100 ml cultured cell amount.
Introduction
- Toxicity of heavy metals
- Methods for removal of heavy metals in wastewater
- Chemical methods
- Physical methods
- Biological methods
- Mechanisms of biosorption
- Metal binding peptides
- Factors affecting biosorption
- pH
- Temperature
- Initial metal ion concentration
- Concentration of biomass
- Zinc oxide nanoparticles
- Antibiotics mechanism of ZnO NPs
- ZnO NPs for applications
- Synthesis of ZnO NPs
The treatment of heavy metals in waste water is classified and is carried out in three stages [3]. The chemical methods for removing heavy metals in wastewater are mainly hydrometallurgical methods involving chemical precipitation, electrochemical processes, oxidation/reduction, acid or base leaching, solvent extraction or a combination of the processes. Electrochemical treatment of heavy metals is known as a very efficient method for industrial wastewater treatment, especially for the removal of heavy metal ions [11].
Electrochemical technology offers solutions for recovering heavy metals in their most valuable state. Biological methods have been proposed as an efficient strategy to remove heavy metals from wastewater. Also, the low price and low sludge production are the main advantages of the biological treatment of heavy metals [13].
In addition, the use of microbial biomass as a platform for heavy metal removal is an alternative method. It has been established that microorganisms are capable of efficiently accumulating heavy metals in a living and dead state [18]. Bacteria, yeasts, fungi and species of algae can absorb and accumulate heavy metals in their body [13].
And the chemical and physical methods that usually use chemical adsorbents for the removal of heavy metals from industrial wastewater have several disadvantages including economic and environmental aspects [26]. It is therefore essential to consider cost-effective and environmentally friendly methods towards the recovery of heavy metals. Surface engineering of gram negative bacteria towards biosorption of heavy metals are reviewed in this study.
Today, bacteria and higher organisms have evolved resistance mechanisms to heavy metals to render them harmless [20]. It removes heavy metals by adsorbing a fusion of anchor motifs and metal-binding peptides. Consideration of the relative affinities of metal-binding peptides and the cell wall to the metal ion should be considered in the rational design of peptide sequences that have specificity for certain heavy metals.
This made it necessary to have a cost-effective treatment method capable of removing heavy metals. Through these three steps, metal binding peptides are made and heavy metals are adsorbed to the created metal binding peptides.
Experimental method
- Bacterial strains and growth conditions
- Cell preparation
- Zinc oxide nanoparticles preparation
- Zinc recovery and analysis
- Affecting factors of zinc uptake in biosorption
- Effect of pH in biosorption
- Effect of temperature in biosorption
- Isotherms at different temperatures
After the adsorption, the recombinant strains were washed twice with 0.85% (w/v) NaCl to remove physically adsorbed zinc. The adsorbed zinc of the peptides was eluted by incubation with 5 mM EDTA for 30 min in ice. Samples were measured quantitatively with 10-fold dilution with water by inductively coupled plasma optical emission spectroscopy (ICP-OES) (Agilent technologies 5110).
Incubation was varied at a wide pH range (pH 1–11) to investigate the effect of pH in biosorption on the zinc recovery. Incubation was separated at different temperatures (20-35 ℃) to analyze the effect of temperature in biosorption on the zinc recovery. The pseudo-first-order and pseudo-second-order models were used to describe the kinetic behavior of the biosorption of Zn(II) by the recombinant E.
Langmuir and Freundlich models were used to obtain equilibrium parameters, such as the maximum adsorption capacity of recombinant E.
![Table 1. List of bacterial strains, peptides, and plasmids used in this study [51].](https://thumb-ap.123doks.com/thumbv2/123dokinfo/10407586.0/26.892.139.799.168.445/table-list-bacterial-strains-peptides-plasmids-used-study.webp)
Results and discussion
- Zinc biosorption by engineered bacteria
- Zinc ( II ) uptake
- Biosynthesis of zinc oxide nanoparticles
- Effect of synthesis temperature in calcination
- Antibiotics of zinc oxide nanoparticles
- Compare the methods of zinc desorption
Effect of adsorption pH on the biosorption of zinc in 100 ml cultured cell volume. Results of the process occurred in this work with the maximum biosorption of zinc (86%) at the neutral pH of 7. Effect of adsorption temperature on the biosorption rate of zinc in 100 ml cultured cell volume.
The experimental biosorption data were fitted with Langmuir and Freundlich isotherm models to explain the adsorption behavior of Zn(II) by engineered E. In this work, an increase in temperature (except from 30 ℃ to 35 ℃) resulted in a higher maximum. zinc biosorption, with the highest at 30. After washing, cell pellets were resuspended in autoclaved double-distilled water, followed by dropwise addition of zinc nitrate solution.
Several different structures of ZnO NPs generated in this experiment are shown, such as round hexagonal granules, etc. For comparison, the structure and size of experimentally produced ZnO NPs and that of other biosyntheses were compared (Fig. In ZnO NPs produced by other biosyntheses, head-to-head fusion, hexagonal rods, side fusion are seen or small round shapes.
The ZnO NPs generated in this work also appear to have a hexagonal rod or small round shape and are somewhat similar in size. In this EDS analysis, zinc and oxygen were observed in a similar ratio, indicating that ZnO NPs were formed. In addition to zinc and oxygen, carbon, nitrogen, sulfate, and others are also observed, which is thought to be observed because E. So, if we want to obtain a higher purity of ZnO NPs in this experiment, we will have to react at a temperature on E. Effect of synthesis temperature on calcination.
The structure of the ZnO NPs produced in this experiment was mainly observed as a head-head fusion, hexagonal rod structure in Fig.14. To confirm the antibiotic properties of ZnO NPs, the synthesized ZnO NPs were added to the 100 mL cultured broth and the optical density was observed every hour. When comparing the amount of metal desorbed by physical method and metal desorbed by chemical method, the efficiency of the physical method was not low, although the efficiency of physical method was inferior to the chemical method.
Conclusion
