Phycoremediation of synthetic dyes in an aqueous solution using an indigenous Oscillatoria sp., from Ethiopia

Abstract

Synthetic dyes usages are inevitable, but they are recalcitrant and toxic, hence need treatment before discharge. Lately, phycoremediation of dyes gained more attention due to its value-added benefits, however, it need more investigation of indigenous species for ease. Therefore, the aim of the study was to isolate indigenous microalgae from Elias Tesfaye textile factory runoff, Addis Ababa. The sample was inoculated to Bold’s Basal Medium and incubated for 15 days and the dominant colonies were purified and identified using a microscope. The identified isolate, Oscillatoria sp., which belongs to prokaryotic filamentous cyanobacteria was checked for the dye removal efficiency and biomass production using synthetic dyes of malachite green (MG), methylene blue (MB) and Safranin (SF). The axenic cultures of Oscillatoria sp., was inoculated (0.2 g/L) with various concentrations of dyes (1-5 mg/L) and incubated under Sunlight for 5 days and analyzed the residual color absorbance and biomass production. A maximum of 93% dye color was removed in MG, followed by MB (66%) and SF (52%). Interestingly, the biomass was increased 3.75 times in MB dye (0.75 g/L), while 3.1 and 1.9 times in MG (0.63 g/L) and SF (0.38 g/L), respectively. It seems that the Oscillatoria sp., was decolorizing the dyes by utilizing as nutrients and shown unique potentials on different dyes. Yet, more studies are needed for the exact mechanism of removal and large scale application. This Ethiopian native species of microalgae can be used effectively for the phycoremediation of synthetic dyes locally.

Keywords

• Biomass, Cyanobacteria, Microalgae, Phycoremediation, Synthetic dyes