Studying of bioremediation processes of some metals carried out by microorganisms

Author: Nino Nikolashvili
Keywords: Bioremediation, Heavy metals, Cyanobacteria-Spirulina platensis
Annotation:

The heavy metal pollution of natural resources constitutes the accompanying problem of contemporary life violating ecological balance of environment. These effects have a negative impact on human health and biodiversity. Prolonged exposure to heavy metals and their accumulation may have dangerous toxic effects. The heavy metals are characterized by sustainability, bioaccumulation and biomagnification. Consequently, development and implementation of effective environmental cleaning and decontamination methods are of the great importance. Bioremediation is one of the successful method for the restoration of contaminated environment using of living organisms, which remove the pollutants, transform them into less toxic/non-toxic forms. The heavy metals salts are commonly diluted in water and their separation by means of common physical and chemical methods (chemical sedimentation, filtration, reverse osmosis, membrane technologies) is impossible. Separation can be done by alternative biological method - biosorption. The purpose of current research is to study biosorption properties of the Blue-Green algae Cyanobacteria- Spirulina platensis intact cells in controlled laboratory conditions. The ability of Spirulina platensis components (chlorophyll, carotenoids, phycocyanin) to absorb metal ions - Cr (III), Cr (VI) and Zn (II) has been revealed by the assessment of absorption spectrum changes. The different effectiveness in biosorbtion ability of Spirulina platensis for Cr (III), Cr (VI) and Zn (II) metal ions have been shown. As a result of association of metal ions with cyanobacteria components (chlorophyll, carotenoids, phycocyanin), the absorption intensity has been decreased. The obtained results have been characterized by the binding constants which were determined on 440 nm, 621 nm, 681 nm wavelength, according to Freundlich equation. On the basis of obtained results, we can assume that the biosorption of the zinc ion is most effective (with binding constant logarithm -3.52) in comparison to other three metals; The effectiveness of the biosorption of Cr (III) and Cr (VI) ions is lower than Zn (II) - in case of Cr (VI) the maximum absorption amplitude decreased to 55.88% on 621 nm wavelength (the maximum amount of phycocyanin absorption) with binding constant logarithm -4.44. As for Cr (III) the absorption intensity change decreased to 76.77% on 821 nm wavelength (chlorophyll absorption spectrum) and the binding constant logarithm is -4.69.

Lecture files:

მიკროორგანიზმების მეშვეობით ზოგიერთი მეტალის ბიორემედიაციული პროცესების შესწავლა [ka]