Physiological and Biochemical Changes Reveal Differential Patterns of Docosahexaenoic Acid Partitioning in Two Marine Algal Strains of Isochrysis.

Zheng Sun,Yong Chen,Jin Liu,Xuemei Mao

doi:10.3390/md15110357

Abstract

The marine microalgae Isochrysis are a good producer of natural docosahexaenoic acid (DHA). To better understand the patterns of DHA accumulation and distribution, two Isochrysis strains, CL153180 and CCMP462, were evaluated in this study. In a batch culture, CL153180 showed a decline in DHA content while CCMP462 exhibited a progressive increase during the late growth period when nitrogen was almost exhausted. In response to nitrogen deficiency (ND), both strains showed a considerable increase in neutral lipids (NL) at the expense of glycolipids (GL) but had little variation in phospholipids (PL). In CL153180, the DHA percentage of NL decreased gradually upon ND, while that in CCMP462 increased progressively to 21.4% after 4 days of ND, which is around 5-fold higher than CL153180. Accordingly, in contrast to CL153180 that stored DHA predominantly in GL, CCMP462 accumulated DHA mainly in NL in late days of ND. Taken together, we proposed a working model for the differential DHA partitioning patterns between two Isochrysis strains: for CCMP462, the degradation of GL released free fatty acids including DHA, which was incorporated into NL upon ND; whereas for CL153180, the released DHA from GL might not be incorporated into NL, and, consequently, might be subject to β-oxidation for degradation.

Highlights

As an omega-3 long-chain polyunsaturated fatty acid, docosahexaenoic acid (DHA), represents an essential substance for human metabolism and provides important physiological regulatory functions
The results indicated the important role of nitrogen availability in affecting DHA synthesis and revealed distinct patterns of DHA accumulation and partitioning into neutral lipids between these two algal strains
Yoshioka et al [17] observed that under an irradiance of 20 μmol photons m−2 ·s−1, the biomass concentration of Isochrysis galbana after 6 day of culture increased to 1.09 g·L−1

Summary

Introduction

As an omega-3 long-chain polyunsaturated fatty acid, docosahexaenoic acid (DHA), represents an essential substance for human metabolism and provides important physiological regulatory functions. DHA is a vital component of the brain cell membrane and retina, directly involved in the formation and development of brain cells for thinking and consolidating memory in fetuses and infants [1]. The consumption of supplementary DHA influences infant behavior and reduces the likelihood of developing allergies and colds [2]. DHA improves visual acuity [3] and promotes the development of visual functioning [4]. It is anti-inflammatory, enhances immunity, prevents cardiovascular and cerebrovascular diseases (as well as cancer), and is anti-hypertension [5]. Fish is unable to de novo synthesize DHA but obtains it via bioaccumulation in

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Conclusion