Abstract
Palmitoleic acid, one scarce omega-7 monounsaturated fatty acid, has important applications in the fields of medicine and health products. Tribonema has been considered as a promising candidate for the production of palmitoleic acid due to its high lipid and palmitoleic acid content and remarkable heterotrophic ability. The high-density heterotrophic cultivation of Tribonema minus was conducted in this work, and the highest biomass of 42.9 g L−1 and a relatively low lipid content of 28.7% were observed. To further enhance the lipid and palmitoleic acid accumulation, induction strategies under two regimes of phototrophy and heterotrophy with different conditions were investigated and compared. Results demonstrated encouraging promotions both by heterotrophic and phototrophic ways, and the final lipid contents reached 41.9% and 49.0%, respectively. In consideration of the time cost, however, the induction under heterotrophic conditions was much more advantageous, by which the highest lipid and palmitoleic acid productivities of 1.77 g L−1 d−1 and 924 mg L−1 d−1 were obtained respectively, with the lipid yield on glucose of 0.26 g g−1.
Highlights
Palmitoleic acid (16:1, ω-7), one of omega-7 fatty acids, has been paid increasing attention in recent years due to the immune metabolic effects relevant to chronic metabolic diseases such as obesity, insulin resistance, nonalcoholic fatty liver disease (NAFLD), and atherosclerosis [1]
Palmitoleic acid has been described as a powerful blocker of stearoyl-CoA desaturase 1 (SCD-1), reducing insulin resistance to control obesity [2,8,9]
The low lipid content (e.g., 3.5% for the sea buckthorn berry) or the poor agronomic characteristics of those sources inevitably results in the limitation of producing palmitoleic acid commercially [14,15]
Summary
Palmitoleic acid (16:1, ω-7), one of omega-7 fatty acids, has been paid increasing attention in recent years due to the immune metabolic effects relevant to chronic metabolic diseases such as obesity, insulin resistance, nonalcoholic fatty liver disease (NAFLD), and atherosclerosis [1]. While a large amount of lipid would be synthesized if the T. minus cells were inoculated into the medium, which was deficient in various nutrients and only supplied with glucose as an essential carbon source This was interesting because the previous work mainly focused on the single stress of nitrogen, phosphorus, iron, or salinity [32,33,34,35], and that only performed a slight influence on the lipid accumulation of heterotrophic T. minus [29]. Rather than the phototrophic induction method, the heterotrophic induction was much more advantageous for the fermented T. minus, resulting in the highest lipid and palmitoleic acid productivities of 1.77 g L−1 d−1 and 924 mg L−1 d−1, respectively
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