Ghorbani Elham, Nowruzi Bahareh, Nezhadali Masoumeh, Hekmat Azadeh
Department of Biotechnology, Faculty of Converging Sciences and Technologies, Islamic Azad University, Science and Research Branch, Tehran, Iran.
Department of Biology, Islamshahr Branch, Islamic Azad University, Islamshahr, Iran.
BMC Microbiol. 2022 Feb 17;22(1):58. doi: 10.1186/s12866-022-02471-8.
Cyanobacteria are ecologically significant prokaryotes that can be found in heavy metals contaminated environments. As their photosynthetic machinery imposes high demands for metals, homeostasis of these micronutrients has been extensively considered in cyanobacteria. Recently, most studies have been focused on different habitats using microalgae leads to a remarkable reduction of an array of organic and inorganic nutrients, but what takes place in the extracellular environment when cells are exposed to external supplementation with heavy metals remains largely unknown.
Here, extracellular polymeric substances (EPS) production in strains Nostoc sp. N27P72 and Nostoc sp. FB71 was isolated from different habitats and thenthe results were compared and reported.
Cultures of both strains, supplemented separately with either glucose, sucrose, lactose, or maltose showed that production of EPS and cell dry weight were boosted by maltose supplementation. The production of EPS (9.1 ± 0.05 μg/ml) and increase in cell dry weight (1.01 ± 0.06 g/l) were comparatively high in Nostoc sp. N27P72 which was isolated from lime stones.The cultures were evaluated for their ability to remove Cu (II), Cr (III), and Ni (II) in culture media with and without maltose. The crude EPS showed metal adsorption capacity assuming the order Ni (II) > Cu (II) > Cr (III) from the metal-binding experiments.Nickel was preferentially biosorbed with a maximal uptake of 188.8 ± 0.14 mg (g cell dry wt) crude EPS. We found that using maltose as a carbon source can increase the production of EPS, protein, and carbohydrates content and it could be a significant reason for the high ability of metal absorbance. FT-IR spectroscopy revealed that the treatment with Ni can change the functional groups and glycoside linkages in both strains. Results of Gas Chromatography-Mass Spectrometry (GC-MS) were used to determine the biochemical composition of Nostoc sp. N27P72, showed that strong Ni (II) removal capability could be associated with the high silicon containing heterocyclic compound and aromatic diacid compounds content.
The results of this studyindicatede that strains Nostoc sp. N27P72 can be a good candidate for the commercial production of EPS and might be utilized in bioremediation field as an alternative to synthetic and abiotic flocculants.
蓝藻是具有重要生态意义的原核生物，可在重金属污染环境中发现。由于其光合机制对金属有很高需求，这些微量营养素的稳态在蓝藻中已得到广泛研究。最近，大多数研究集中在使用微藻的不同生境导致一系列有机和无机营养素显著减少，但当细胞暴露于重金属外部补充时，细胞外环境中会发生什么仍 largely unknown。
在此，从不同生境分离出 Nostoc sp. N27P72 和 Nostoc sp. FB71 菌株中的胞外聚合物（EPS），然后比较并报告结果。
分别用葡萄糖、蔗糖、乳糖或麦芽糖补充的两种菌株培养物表明，补充麦芽糖可提高 EPS 产量和细胞干重。从石灰岩中分离出的 Nostoc sp. N27P72 中 EPS 产量（9.1±0.05μg/ml）和细胞干重增加（1.01±0.06g/l）相对较高。评估了培养物在有和没有麦芽糖的培养基中去除 Cu（II）、Cr（III）和 Ni（II）的能力。从金属结合实验来看，粗 EPS 显示出金属吸附能力，顺序为 Ni（II）>Cu（II）>Cr（III）。镍被优先生物吸附，粗 EPS 对镍的最大吸收量为 188.8±0.14mg/（g 细胞干重）。我们发现使用麦芽糖作为碳源可增加 EPS、蛋白质和碳水化合物含量的产生，这可能是其高金属吸收能力的一个重要原因。傅里叶变换红外光谱（FT-IR）显示，镍处理可改变两种菌株中的官能团和糖苷键。气相色谱-质谱联用（GC-MS）结果用于确定 Nostoc sp. N27P72 的生化组成，表明强 Ni（II）去除能力可能与高含硅杂环化合物和芳香二酸化合物含量有关。
本研究结果表明，Nostoc sp. N27P72 菌株可能是 EPS 商业生产的良好候选者，并且可作为合成和非生物絮凝剂的替代品用于生物修复领域。
