Lipid Production in Nannochloropsis gaditana during Nitrogen Starvation.

Jorijn H Janssen,Maria J Barbosa,René H Wijffels

doi:10.3390/biology8010005

Jorijn H Janssen, Maria J Barbosa + Show 1 more

Open Access

https://doi.org/10.3390/biology8010005

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Abstract

The microalga Nannochloropsis gaditana is a natural producer of triacylglycerol (TAG) and the omega-3 fatty acid eicosapentaenoic acid (EPA). TAG accumulation is induced by nitrogen starvation. The biomass-specific photon supply rate used had an effect on EPA and TAG accumulation during nitrogen starvation as well as on the localization of EPA accumulation. Clear differences in TAG yield on light were found for different biomass-specific photon supply rates and light regimes during nitrogen starvation. De novo EPA synthesis or the translocation of EPA between lipid fractions might be limiting for EPA accumulation in TAG. Further studies are needed to fully understand EPA accumulation in TAG during nitrogen starvation. To elucidate the function of EPA in TAG nitrogen recovery, experiments are suggested. The overexpression of genes involved in de novo EPA synthesis and translocation is proposed to elucidate the exact metabolic routes involved in these processes during nitrogen starvation. This work addresses future opportunities to increase EPA accumulation.

Highlights

Microalgae are known for their ability to produce large amounts of lipids, and some species are the primary producers of the omega-3 fatty acid eicosapentaenoic acid (EPA)
The EPA content was highest at the lowest biomass-specific photon supply rate, mainly due to its presence in the polar lipids which are mostly located in the membranes
The EPA accumulation in TAG was lower at the low biomass-specific photon supply rates, which had the highest EPA content in the polar lipids

Summary

Introduction

Microalgae are known for their ability to produce large amounts of lipids, and some species are the primary producers of the omega-3 fatty acid eicosapentaenoic acid (EPA). Different biomass-specific photon supply rates during nitrogen starvation tested for Chromochloris zofingiensis showed no large differences in TAG yield on light [10]. Despite light being the most important and often limiting substrate in microalgae photosynthetic processes, the effects of the biomass-specific photon supply rates and supply mode on TAG and EPA accumulation during nitrogen starvation for Nannochloropsis gaditana were unknown. Different studies describe experiments using various light intensities and initial biomass concentrations at the onset of nitrogen starvation, resulting in various initial average biomass-specific photon supply rates. The incident light intensity, light regime and initial biomass concentration were all different, resulting in different initial average biomass-specific photon supply rates [8,11,12]. In [11], light was supplied as a day:night cycle in a half sinus function instead of a continuous function

Time-Averaged TAG Yield on Light

TAG Content

Findings

Polar Lipids

Conclusions