Tagging of biomolecules with deuterated water (D2O) in commercially important microalgae.

To understand the effect of any biomolecules in specific metabolic pathways in humans, bioavailability and for other basic understanding, stable isotopically-labelled biomolecules (preferably deuterated) is the fundamental pre-requisite. Production of deuterated biomolecules such as, astaxanthin, ß-carotene, lutein, chlorophyll-a, and eicosapentaenoic acid (EPA, 20:5n-3) by metabolic tagging have been shown in commercially important microalgae, Haematococcus pluvialis and Phaeodactylum tricornutum. These microalgae were grown in appropriate optimized medium supplemented with 25% (v/v) deuterated water. LC-MS analysis showed a maximum of 20, 25, 23, 24, and 27% replacement of hydrogen by deuterium atoms respectively in astaxanthin, ß-carotene, lutein, chlorophyll-a, and EPA. To our knowledge, this is the first report on the production of deuterated astaxanthin, chlorophyll-a and EPA by these microalgae.

Effect of various stress-regulatory factors on biomass and lipid production in microalga Haematococcus pluvialis.

To maximize the biomass and lipid production for applications in food or biofuel feedstock, nine stress conditions were tested considering N and/or P limitations, light intensity & quality, for Haematococcus pluvialis SCCAP K-0084 cultivation. Photosynthetically active radiation (PAR), warm white light emitting diode (WWLED), and white light emitting diode (WLED) at illumination of 240 µmol photons m(-2) sec(-1) were the best stress-regulatory factors. PAR without P & low N conditions yielded high biomass with 33% lipids containing increased C16:0 and C18:0 saturated fatty acids, and reduced unsaturated fatty acids (UFAs) (oleic, linoleic, and α/γ-linolenic). WWLED and WLED without P conditions also yielded high biomass, but 25% lipids with increased amounts of UFAs. Red light emitting diode (RLED) without P & low N conditions yielded 46% lipids with lowest biomass. PAR and WWLED & WLED illuminated conditions were found suitable respectively for biodiesel feedstock lipids and UFA-rich lipids for multiple applications.