Variations in Chlorella lipid content in commercial and in-lab produced biomass

Abstract

Microalgae appear as a sustainable source of biomass with relevant nutritional qualities. Still, regulatory restrictions currently limit the use of eukaryotic microalgae for human consumption to a short list of species dominated by Chlorella spp. Chlorella biomass contains valuable proteins but also interesting lipids, including polyunsaturated fatty acids (PUFA) ω3 and ω6. The amount of PUFA and the ω6/ω3 ratio vary significantly depending on the species and cultivation trophic mode. While the lipid profils of in-lab produced Chlorella has been widely studied, the variability of lipid content in commercial biomasses is barely described. Here, lipid classes and fatty acid profiles of six commercial biomasses of Chlorella spp. as well as those of lab-produced C. sorokiniana grown in photo-autotrophy and in four mixotrophy conditions were characterized. Results showed significant lipid composition variations between the biomasses, such as the triacylglycerols/glycolipids and ω6/ω3 contents. The ω6/ω3 ratios were lower in photo-autotrophic mode (2.5) while they ranged between 1.3 and 8.9 in commercial biomasses. The free fatty acids level was also variable (1.4% to 17.9% of total lipids). As a consequence, Chlorella lipid content and quality differed significantly, impacting the potential nutritional benefits of the consumption of commercial biomass. Processing and post-processing conditions should therefore be carefully controlled to optimize lipid profiles.