Fourier transform infrared (FTIR) spectroscopy for identification of Chlorella vulgaris Beijerinck 1890 and Scenedesmus obliquus (Turpin) Kützing 1833

Abstract

Fourier transform infrared (FTIR) spectroscopy was used in this study to identify and determine spectral features of Chlorella vulgaris Beijerinck 1890 and Scenedesmus obliquus (Turpin) Kützing 1833. Two cultures were grown in a chemically-defined media under photoautotrophic culture conditions isolated from eutrophic freshwater lake in Ankara. For FTIR analyses, a view from the transmission region between 4000 and 500 cm^-1 on the microscope was chosen. All FTIR spectra showed a closely similar sequence of 11 distinct bands and were assigned a range of vibrationally active chemical groups, including residual water (–OH), lipid (–CH2), cellulose (–C=O), protein (amide), nucleic acid (>P=O) and starch (–C–O). The nonparametric (Spearman) correlations revealed a high level of correlations between certain bands. Comparison of band intensities (normalized to amide I) using Mann-Whitney test demonstrated major differences in relative band intensities, with bands 1, 3 and 5 to 11 showing significant differences between the two algal species at the 99% significant level. While bands 8, 9 and 10 showed the highest variations (CV>30%) in C. vulgaris, bands 1, 2, 3 and 7 with the highest variations (CV>30%) in S. obliquus. The results show that FTIR technique has the potential to become applicable for the determination of single cell biomass composition from phytoplankton communities.

Key words: Microalgae, Chlorella, Scenedesmus, Fourier transform infrared (FTIR) analysis, infrared spectroscopy.