Biochemistry and Biotechnology of Lipid Accumulation in the Microalga Nannochloropsis oceanica

Abstract

Oils are among the most important agricultural commodities and have wide applications in food/nutrition, biofuels, and oleochemicals. The oleaginous microalga Nannochloropsis oceanica can produce large amounts of oils and the high-value ω-3 eicosapentaenoic acid, which represents a promising resource for oil production targeting biodiesel, nutraceutical, and aquaculture industries. In recent years, with the availability of omics databases and the development of genetic tools, N. oceanica has been extensively investigated as a model photosynthetic organism for studying lipid metabolism and as a green cellular factory to produce lipids for industrial applications. This review summarizes the current knowledge on the lipid composition and biosynthetic pathways of N. oceanica and reviews the recent advances in metabolic engineering of lipid production in this microalga.

Zeaxanthin epoxidase is involved in the carotenoid biosynthesis and light-dependent growth of the marine alga Nannochloropsis oceanica

“…Among them, N. oceanica is cited as the promising next-generation unicellular chassis of eukaryotic algae because of the availability of sequenced and well-annotated haploid genome [ 4 , 5 ], ease of transformation [ 6 ], feasible genetic tools [ 7 – 10 ], and stable transgene expression [ 11 ]. As a potential producer of oil and eicosapentaenoic acid (EPA, an ω3 long-chain polyunsaturated fatty acid of high value), N. oceanica has been well-studied regarding to characterization of key lipid metabolic genes, understanding of regulatory mechanisms underlying lipid metabolism for triacylglycerol assembly and EPA biosynthesis, and metabolic engineering of lipids and fatty acids [ 12 ]. These efforts contribute to the buildup of N. oceanica as an emerging model alga.…”

EPA and DHA in microalgae: Health benefits, biosynthesis, and metabolic engineering advances

“…In wildtype Schizochytrium , Aurantiochytrium , and Crypthecodinium cohnii strains, DHA content ranges from 42.9%–54.5%, 23.9%–52.5%, 24.2%–54.2% of the total fatty acids, respectively (Jovanovic et al, 2021). Photosynthetic microalgae, such as P. tricornutum , N. oceanica , and Dunaliella salina primarily produce EPA up to 36%, 42%, and 46.2% of the total fatty acids, respectively (Jovanovic et al, 2021; Xu, 2022). Though not natural VLC‐PUFA synthesizers, oilseed crops such as Camelina sativa and canola ( Brasscia napus ) have also been successfully bioengineered for EPA and DHA production and represent a promising plant source of these fatty acids.…”

“…These species are natural producers for DHA and/or EPA, have been extensively researched with various genetic modification toolkits and omics databases available and thus have attracted great research attention to engineer VLC‐PUFA accumulation. For comprehensive review of lipid metabolism and VLC‐PUFA content in the individual species, the reader is encouraged to consult three recent reviews (Chi et al, 2022; Xu, 2022; Zulu et al, 2018).…”

“…EPA synthesis in N. oceanica is catalyzed by alternative fatty acid desaturases and elongases, and is considered to occur through the ω ‐3 pathway. Similar to P. tricornutum , N. oceanica stores the majority of its EPA in polar lipids as opposed to TAG, such as monogalactosyldiacylglycerol (MGDG) and diacylglyceryl‐N,N,N‐trimethylhomoserine (DGTS) (Dolch et al, 2017; Xu, 2022). Therefore, some engineering efforts have been focused on increasing EPA assembly into TAG (Table 1) (Xu, 2022).…”

“…accumulation. For comprehensive review of lipid metabolism and VLC-PUFA content in the individual species, the reader is encouraged to consult three recent reviews (Chi et al, 2022;Xu, 2022;Zulu et al, 2018).…”