Metal removal capability of two cyanobacterial species in autotrophic and mixotrophic mode of nutrition

Abstract

Background 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. Methods 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. Result 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) −1 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. Conclusion 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.

Versatile Applications of Cyanobacteria in Biotechnology

“…A microorganism growing as a biofilm expressed the ability to adsorb Cd(II) in a wide concentration range of ~24 ppb to 100 ppm and a pH range of 5 to 9. Strains belonging to Nostoc genera that produce EPS are known for their ability to remove metals, and the application of mixotrophic cultivation conditions increased the uptake capacity of heavy metal ions by the Nostoc species [155]. The self-flocculating Oscillatoria sp.…”

Biological potential of polysaccharides extracted from Nostoc colonies for film production – Physical and biological properties

“…[ 3–8 ] Additionally, in the latest studies, the possibility of using cyanobacteria as bioremediators for the removal of heavy metals (Ni 2+ , Cu 2+ , Cr 3+ ) from soils and waters has been suggested. [ 9,10 ]…”

“…[3][4][5][6][7][8] Additionally, in the latest studies, the possibility of using cyanobacteria as bioremediators for the removal of heavy metals (Ni 2+ , Cu 2+ , Cr 3+ ) from soils and waters has been suggested. [9,10] The Nostoc species, as most of other cyanobacteria, are able to synthesize and secrete biopolymers -extracellular polymeric substances (EPS). We distinguish different fractions of EPS: (1) composed mainly of polysaccharides associated with the cell surface (in the form of sheaths, capsules, or slime), and (2) released into the extracellular matrixreleased polysaccharides (RPS).…”

The Remediation of Dysprosium-Containing Effluents Using Cyanobacteria Spirulina platensis and Yeast Saccharomyces cerevisiae

“…The use of yeast and cyanobacterial biomass is actively explored for heavy metals, including rare earth elements’ removal from batch systems and real wastewater [ 23 , 24 , 25 , 26 , 27 , 28 ]. Thus, wild and rim20∆ Saccharomyces cerevisiae strains showed high biosorption capacities toward lanthanum ions, 40 and 70 mg/g, respectively [ 29 ].…”