The Nutritional and Pharmacological Potential of New Australian Thraustochytrids Isolated from Mangrove Sediments

Abstract

Mangrove sediments represent unique microbial ecosystems that act as a buffer zone, biogeochemically recycling marine waste into nutrient-rich depositions for marine and terrestrial species. Marine unicellular protists, thraustochytrids, colonizing mangrove sediments have received attention due to their ability to produce large amounts of long-chain ω3-polyunsaturated fatty acids. This paper represents a comprehensive study of two new thraustochytrids for their production of valuable biomolecules in biomass, de-oiled cakes, supernatants, extracellular polysaccharide matrixes, and recovered oil bodies. Extracted lipids (up to 40% of DW) rich in polyunsaturated fatty acids (up to 80% of total fatty acids) were mainly represented by docosahexaenoic acid (75% of polyunsaturated fatty acids). Cells also showed accumulation of squalene (up to 13 mg/g DW) and carotenoids (up to 72 µg/g DW represented by astaxanthin, canthaxanthin, echinenone, and β-carotene). Both strains showed a high concentration of protein in biomass (29% DW) and supernatants (2.7 g/L) as part of extracellular polysaccharide matrixes. Alkalinization of collected biomass represents a new and easy way to recover lipid-rich oil bodies in the form of an aqueous emulsion. The ability to produce added-value molecules makes thraustochytrids an important alternative to microalgae and plants dominating in the food, pharmacological, nutraceutical, and cosmetics industries.

Physicochemical Characteristics of Protein Isolated from Thraustochytrid Oilcake

“…The lower purify of TPI extracted at a high temperature can be attributed to the increased extraction of extracellular polysaccharide substances (EPS). Thraustochytrids secrete EPS as part of their metabolism and remain attached to their cells [15,35]. A similar increase in protein yield was reported in other studies that evaluated the effects of pH and temperature during the alkaline extraction of proteins.…”

“…Two Australian strains of thraustochytrids, grouped into the genera Aurantiochytrium and designated as MAN65 and MAN70 (GenBank accession numbers MH790117, described in Nham Tran, Miranda [15]) were used. Both strains were grown using 3% (w/v) of glucose with 0.5% yeast extract and 1% tryptone in 50% seawater for seven days.…”

“…Earlier, we showed that thraustochytrid species MAN65 and MAN70 are rich in oil (up to 40% DW), which is rich in DHA, squalene, carotenoids and proteins [15]. Thermal stability of the oil is essential for processing and use and was measured in oils from both MAN65 and MAN70 using DSC (−20 • C to 60 • C) and TGA (30 • C to 600 • C).…”

“…The biomass from thraustochytrid species, which also contains carotenoids, proteins, and squalene, have been designated as Generally Recognized as Safe by the U.S. Food and Drug Administration (FDA) [19]. Thraustochytrids can also produce up to 38% dry weight (dw) of protein [15], which is lower in comparison to some common microalgae, such as Spirulina sp. (50-70% protein/dw) or Chlorella sp.…”

“…Earlier, we showed that the oil isolated from thraustochytrid species could be used as a valuable source of docosahexaenoic acid (DHA), squalene, carotenoids and proteins [15]. In this study, we aimed to extract and characterize thraustochytrid protein isolate (TPI) from their oilcake to add value.…”