Rapid detection and quantification of haptophyte alkenones by Fourier transform infrared spectroscopy (FTIR)

Abstract

Several haptophyte algae produce unique neutral long-chain (C37C40) ketones (alkenones) with two to four trans-carbon-carbon double (CC) bonds and a keto-group. These molecules are of great biological interest and may have substantial commercial relevance as biofuel sources. Unfortunately, their detection and quantification, involving extraction from cells with organic solvents and fractionation of lipids through columns, are rather cumbersome. Hence, we developed a method for the rapid and reliable quantification of alkenones in intact cells using Fourier transform infrared spectroscopy (FTIR). The method is based on the absorption band at 962.5cm−1, which corresponds to a trans-CC bond that is unequivocally attributable to alkenones. This peak was exclusively observed in alkenone-producing haptophytes such as Emiliania huxleyi NIES-837, Emiliania huxleyi CCMP 2090, Tisochrysis lutea (former Isochrysis galbana T-iso), Tisochrysis lutea CCMP 463, and Chrysotila lamellosa CCMP 1307, as well as in appropriate standards. We compared our FTIR method with a typical GC analysis method. The alkenone quantity determined by these two methods showed similar values. Nevertheless, the FTIR method developed in this study does not require complex extraction procedures and is therefore a much easier and rapid quantification method. This FTIR method can also be used for the screening of strains and the optimization of culture conditions for alkenone production.