Biomass characterisation and phylogenetic analysis of microalgae isolated from estuaries: Role in phycoremediation of tannery effluent

Chrome tanning activity has contributed intensively towards environmental pollution in the form of effluents. To study the specific contribution of microalgae towards phycoremediation, four heavy-metal tolerant microalgal species were isolated from the estuaries receiving tannery effluents, and their biomass was examined by their interaction. The sequences of the four microalgal species, namely Anabaena (VITMA1), Oscillatoria acuminate (VITMA2), Phormidium irriguum (VITMA3) and Spirogyra maxima (VITMA4), were clustered after isolating their ribosomal DNA. Phylogenetic analysis revealed that VITMA1 showed a distant relationship with Anabaena, having only 63% sequence similarities, and other species such as VITMA2, VITMA3 and VITMA4 showed 82%, 95% and 92% sequence similarities, respectively. Microalgal species were grown in BG11 media along with chromium-contaminated tannery effluents for analysing their growth, biomass and protein contents. The binding site characterisation was assessed by Fourier transform infrared spectroscopy, nuclear magnetic resonance and X-ray diffraction spectral studies. The results obtained from these studies advocate that the interactions are due to the presence of alkynes and aromatic functional groups. Scanning electron microscopy analysis showed the presence of intact cells with chromium accumulation. The biosorption activity was found to be 90% for O.acuminate (VITMA2), followed by 80% for P. irriguum (VITMA3), 65% for Anabaena (VITMA1) and 55% for S. maxima (VITMA4), respectively, and proves their impressive potential for phycoremediation activity.