Influence of high pressure homogenization on free fatty acid formation in Nannochloropsis sp

Abstract

Although Nannochloropsis lipids have many potential applications in biofuels and high value products, their extraction is limited by the tough cell wall of this species. High pressure homogenization (HPH) can be used to improve the extraction efficiency. However, this can possibly induce free fatty acid (FFA) formation, which has a negative impact on oil quality. In this study, the HPH pressure and number of passes were varied in a full factorial design to study the impact of these factors on FFA formation, lipid extraction efficiency and fatty acid profile.

It was found that substantial amounts of FFA were formed during HPH treatments when compared to the non-disrupted biomass. The FFA formation was mostly influenced by the number of passes applied, which can explained by a combined effect of the longer time residing as a wet paste and the temperature increase during the treatment. The large amount of FFA formed during the least intensive HPH treatment is in contrast with only a slight increase of the lipid extraction efficiency, which indicates that minor damage to the cell is sufficient to induce lipolytic reactions. The relative fatty acid profile after HI extraction was not influenced by the HPH treatment.

Practical applications: These results have important implications for the application of HPH treatments on microalgae with the aim to improve the extraction efficiency. It was demonstrated that more intensive HPH treatments with several passes are necessary to improve the extraction efficiency of Nannochloropsis lipids. However, the least intensive HPH treatments (1 pass at 400 bar) already induced the formation of substantial amounts of FFA. Consequently, to produce a biomass with a low FFA content and a high lipid extraction efficiency, a compromise should thus be made.

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