Mechanisms of Sodium-Acetate-Induced DHA Accumulation in a DHA-Producing Microalga, Crypthecodinium sp. SUN

Abstract

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid (PUFA) that is critical for the intelligence and visual development of infants. Crypthecodinium is the first microalga approved by the Food and Drug Administration for DHA production, but its relatively high intracellular starch content restricts fatty acid accumulation. In this study, different carbon sources, including glucose (G), sodium acetate (S) and mixed carbon (M), were used to investigate the regulatory mechanisms of intracellular organic carbon distribution in Crypthecodinium sp. SUN. Results show that glucose favored cell growth and starch accumulation. Sodium acetate limited glucose utilization and starch accumulation but caused a significant increase in total fatty acid (TFA) accumulation and the DHA percentage. Thus, the DHA content in the S group was highest among three groups and reached a maximum (10.65% of DW) at 96 h that was 2.92-fold and 2.24-fold of that in the G and M groups, respectively. Comparative transcriptome analysis showed that rather than the expression of key genes in fatty acids biosynthesis, increased intracellular acetyl-CoA content appeared to be the key regulatory factor for TFA accumulation. Additionally, metabolome analysis showed that the accumulated DHA-rich metabolites of lipid biosynthesis might be the reason for the higher TFA content and DHA percentage of the S group. The present study provides valuable insights to guide further research in DHA production.

Regulatory mechanisms of autophagy on DHA and carotenoid accumulation in Crypthecodinium sp. SUN

“…Glucose is the substrate for starch synthesis in microalgae [ 9 ]. Glucose transporter (GLUT) is a membrane protein that transports glucose into the cell, which is the first step in glucose metabolism in microalgae [ 45 ].…”

“…In addition, key genes in the TAG biosynthesis pathway were analyzed. Glycerol-3-phosphate O-acyltransferase (GPAT) is the rate-limiting enzyme in the TAG biosynthesis pathway, which catalyzes the formation of 1-acyl-glycerol 3-phosphate from glycerol-3-phosphate [ 9 ]. GPAT was downregulated in the 3-MA group.…”

“…1 mL culture was subjected to centrifugation (8000 rpm for 5 min) and the supernatant was used to measure the glucose consumption. Briefly, 200 μL supernatant was added to a tube, followed by 1 mL 3,5-dinitrosalicylic acid (DNS), and incubated at 100 ℃ [ 9 , 55 ]. The absorbance at 570 nm was measured using a microplate reader (SpectraMax iD3, Molecular Devices, Shanghai, China).…”

“…sp. SUN showed that the supply of different precursors might also lead to different patterns of accumulation of storage compounds [ 9 ]. These studies suggest that the relationship between starch and fatty acids is more complicated than simple competition for carbon sources and energy.…”

Oleaginous Heterotrophic Dinoflagellates—Crypthecodiniaceae

“…Crypthecodinium cohnii sensu lato is employed for the industrial production of omega-3 docosahexaenoic acid (DHA), which is crucial for neuronal and infant health [ 1 ]. C. cohnii can accumulate lipids with high DHA content [ 2 , 3 , 4 , 5 ] and was the first algae approved by U.S. Food and Drug Administration for DHA production. Dinoflagellates from the family Crypthecodiniaceae, hitherto with only one partially described species, Crypthecodinium cohnii (= Crypthecodinium setense ) [ 6 ], is composed of multiple undescribed taxonomic units (OTUs) commonly isolated from decaying seaweed on shore [ 7 , 8 , 9 , 10 , 11 ].…”