Rapid Detection and Quantification of Alkenones, Unique Storage Lipids of Haptophytes, by Fourier Transform Infrared Spectroscopy (FTIR).

Several haptophyte algae produce unique neutral long-chain (C37\\C40) ketones (alkenones) with two to four trans-carbon-carbon double (C_C) bonds and a keto-group. These molecules are of great biological interest andmay have substantial commercial relevance as biofuel sources. Unfortunately, their detection and quantification, involving extraction fromcellswith organic solvents and fractionation of lipids through columns, are rather cumbersome. Hence,we developed amethod for the rapid and reliable quantification of alkenones in intact cells using Fourier transforminfrared spectroscopy (FTIR). Themethod is based on the absorption band at 962.5cm−1, which corresponds to a trans-C_C 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 twomethods 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 FTIRmethod can also be used for the screening of strains and the optimization of culture conditions for alkenone production.