Astaxanthin accumulation in Haematococcus pluvialis observed through Fourier-transform infrared microspectroscopy imaging

Abstract

Haematococcus pluvialis has emerged as a promising microalga for its rapid accumulation of astaxanthin. However, the underlying mechanism for astaxanthin biosynthesis is still unclear and needs further exploring in terms of the chemical changes of algal cell during the carotenogenesis pathway. In this study, the chemical changes were monitored in the algal cells exposed to carotenogenesis inhibitors by Fourier-transform infrared (FTIR) microspectroscopy imaging. The significant increase of signals at 3010 and 2925 cm−1 suggests the accumulation of carotenoids during the algal cell encysting. In contrast, a relatively low level of carotenoids in the algal cells contacted to nicotine and diphenylamine were observed for the biosynthesis blocking of β-carotene and astaxanthin. The decrease of the absorbance at 1740 and 1650 cm−1 indicates that lipids, proteins and astaxanthin biosynthesis were also inhibited by nicotine and diphenylamine while the cell wall biosynthesis was not disturbed by the inhibitors for the strong absorbance band at 1035 cm−1 assigned to polysaccharides. This work demonstrates that FTIR microspectroscopy imaging is an effective and none-invasive tool to analyze chemical changes and the components location in the single algal cell with high spatial resolution and it facilitates the study of carotenoid biosynthetic pathway.