Enrichment of DPAn-6 and DHA from Schizochytrium sp. Oil by Low-Temperature Solvent Crystallization

Harnessing oleaginous protist Schizochytrium for docosahexaenoic acid: Current technologies in sustainable production and food applications

Docosahexaenoic acid (DHA) exerts versatile roles in nutrition supplementation and numerous health disorders prevention. Global consumption demand for DHA has also been consistently increasing with enhanced health awareness. Oleaginous marine protist Schizochytrium is praised as a potential DHA source due to short growth cycle, convenient artificial culture, harmless to the human body, and easy manipulation of the DHA synthesis pathway. However, factors including strain performances, fermentation parameters, product harvest and extraction strategies, safety and stability maintenance, and also application limitations in health and functional properties affect the widespread adoption of Schizochytrium DHA products. This review provides a comprehensive summary of the current biotechnologies used for tackling factors affecting the Schizochytrium DHA production, with special focuses on Schizochytrium strain improvement technologies, fermentation optimization projects, DHA oil extraction strategies, safety evaluations and stability maintenance schemes, and DHA product application approaches in foods. Inspired by systematic literature investigations and recent advances, suggestive observations composed of improving strain with multiple breeding technologies, considering artificial intelligence and machine learning to optimize the fermentative process, introducing nanoparticles packing technology to improve oxidation stability of DHA products, covering up DHA odor defect with characteristic flavor foods, and employing synthetic biology to construct the structured lipids with DHA to exploit potential functions are formed. This review will give a guideline for exploring more Schizochytrium DHA and propelling the application development in food and health.

Reversed-Phase Medium-Pressure Liquid Chromatography Purification of Omega-3 Fatty Acid Ethyl Esters Using AQ-C18

Omega-3 fatty acids are in high demand due to their efficacy in treating hypertriglyceridemia and preventing cardiovascular diseases. However, the growth of the industry is hampered by low purity and insufficient productivity. This study aims to develop an efficient RP-MPLC purification method for omega-3 fatty acid ethyl esters with high purity and capacity. The results indicate that the AQ-C18 featuring polar end-capped silanol groups outperformed C18 and others in retention time and impurity separation. By injecting pure fish oil esters with a volume equivalent to a 1.25% bed volume on an AQ-C18 MPLC column using a binary isocratic methanol-water (90:10, v:v) mobile phase at 30 mL/min, optimal omega-3 fatty acid ethyl esters were obtained, with the notable purity of 90.34% and a recovery rate of 74.30%. The total content of EPA and DHA produced increased from 67.91% to 85.27%, meeting the acceptance criteria of no less than 84% set by the 2020 edition of the Pharmacopoeia of the People's Republic of China. In contrast, RP-MPLC significantly enhanced the production efficiency per unit output compared to RP-HPLC. This study demonstrates a pioneering approach to producing omega-3 fatty acid ethyl esters with high purity and of greater quantity using AQ-C18 RP-MPLC, showing this method's significant potential for use in industrial-scale manufacturing.

Characterization and Optimization of Culture Conditions for Aurantiochytrium sp. SC145 Isolated from Sand Cay (Son Ca) Island, Vietnam, and Antioxidative and Neuroprotective Activities of Its Polyunsaturated Fatty Acid Mixture

Aurantiochytrium is a heterotrophic marine microalga that has potential industrial applications. The main objectives of this study were to isolate an Aurantiochytrium strain from Sand Cay (Son Ca) Island, Vietnam, optimize its culture conditions, determine its nutritional composition, extract polyunsaturated fatty acids (PUFAs) in the free (FFA) and the alkyl ester (FAAE) forms, and evaluate the antioxidation and neuroprotection properties of the PUFAs. Aurantiochytrium sp. SC145 can be grown stably under laboratory conditions. Its culture conditions were optimized for a dry cell weight (DCW) of 31.18 g/L, with total lipids comprising 25.29%, proteins 7.93%, carbohydrates 15.21%, and carotenoid at 143.67 µg/L of DCW. The FAAEs and FFAs extracted from Aurantiochytrium sp. SC145 were rich in omega 3-6-9 fatty acids (40.73% and 44.00% of total fatty acids, respectively). No acute or subchronic oral toxicity was determined in mice fed with the PUFAs in FFA or FAAE forms at different doses over 90 days. Furthermore, the PUFAs in the FFA or FAAE forms and their main constituents of EPA, DHA, and ALA showed antioxidant and AChE inhibitory properties and neuroprotective activities against damage caused by H₂O₂- and amyloid-ß protein fragment 25-35 (Aβ_25-35)-induced C6 cells. These data suggest that PUFAs extracted from Aurantiochytrium sp. SC145 may be a potential therapeutic target for the treatment of neurodegenerative disorders.

Enzymatic enrichment of n-3 polyunsaturated fatty acid glycerides by selective hydrolysis

Most natural oils are low in n-3 polyunsaturated fatty acids (n-3 PUFAs) content, which limits their application in health products. In this study, n-3 PUFAs in glyceride form were selectively enriched by lipase-mediated hydrolysis of n-3 PUFA-containing oils. First, commercial lipases were screened, and the lipase AY "Amano" 400SD from Candida cylindracea was the best choice in producing n-3 PUFA glycerides from tuna oil. Subsequently, the hydrolysis conditions were optimized. Under the optimal conditions, the highest n-3 PUFA content in the glyceride fraction was found to be 57.7% after enzymatic hydrolysis. Addition of Ca²⁺ to the system significantly shortened the reaction time from 10 to 4 h. When algal oil was used as substrate, total PUFA contents in the glyceride fraction were 89.9%. This study provides an efficient enzymatic process to produce n-3 PUFA-enriched glyceride concentrates and demonstrates that AY "Amano" 400SD can effectively discriminate against n-3 PUFAs during hydrolysis.

Synthesis of DHA/EPA Ethyl Esters via Lipase-Catalyzed Acidolysis Using Novozym® 435: A Kinetic Study

DHA/EPA ethyl ester is mainly used in the treatment of arteriosclerosis and hyperlipidemia. In this study, DHA+EPA ethyl ester was synthesized via lipase-catalyzed acidolysis of ethyl acetate (EA) with DHA+EPA concentrate in n-hexane using Novozym® 435. The DHA+EPA concentrate (in free fatty acid form), contained 54.4% DHA and 16.8% EPA, was used as raw material. A central composite design combined with response surface methodology (RSM) was used to evaluate the relationship between substrate concentrations and initial rate of DHA+EPA ethyl ester production. The results indicated that the reaction followed the ordered mechanism and as such, the ordered mechanism model was used to estimate the maximum reaction rate (Vmax) and kinetic constants. The ordered mechanism model was also combined with the batch reaction equation to simulate and predict the conversion of DHA+EPA ethyl ester in lipase-catalyzed acidolysis. The integral equation showed a good predictive relationship between the simulated and experimental results. 88–94% conversion yields were obtained from 100–400 mM DHA+EPA concentrate at a constant enzyme activity of 200 U, substrate ratio of 1:1 (DHA+EPA: EA), and reaction time of 300 min.

Synthesis of docosapentaenoic acid-enriched diacylglycerols by enzymatic glycerolysis of Schizochytrium sp. oil

Utilization of algae oil and glycerol for preparation of value-added products is vital for sustainable development of related industries. In this study, we aimed to prepare highly pure diacylglycerols (DAG) rich in docosapentaenoic acid (DPA). First, content of DPA in form of triacylglycerols (TAG) increased from 16.4% to 28.1% after low-temperature crystallization of Schizochytrium sp. oil at -80 °C for 6 h. Subsequently, DPA-enriched DAG was prepared by the enzymatic glycerolysis of the enriched oil. Under the optimum conditions, there was 48.4% DAG produced in the crude mixture. To remove polar impurities from the crude product, a novel two-step purification was developed and the final product consisted of 75.1% DAG and 24.9% TAG with a low peroxide value. The current method for the synthesis of DAG rich DPA is effective and relatively mild and the successful preparation of value-added product will reduce production costs for algae and biodiesel industries.