Electron microscopy may reveal structure of docosahexaenoic acid‐rich oil withinSchizochytriumsp

Abstract

Schizochytrium sp. is an algae-like microorganism utilized for commercial production of docosahexaenoic acid (DHA)-rich oil and dried microalgae for use as a source of DHA in foods, feeds, and nutritional supplements. Electron microscopic analysis of whole cells of Schizochytrium sp. employing sample preparation by high-pressure freeze substitution suggests the presence of secondary and tertiary semicrystalline structures of triacylglycerols within the oil bodies in Schizochytrium sp. A fine secondary structure consisting of alternating light- and dark-staining bands was observed inside the oil bodies. Dark bands were 29 +/- 1 A in width, and light bands were 22 +/- 1 A in width. The tertiary (three-dimensional) structure may be a multilayered ribbon-like structure which appears coiled and interlaced within the oil body. In freeze-fracture photomicrographs, Schizochytrium oil bodies exhibited fracture planes with terraces averaging 52 +/- 7 A in height which could correspond to the combined width of two halves of two light bands and one dark band observed in the high-pressure freeze substitution photomicrographs. The results suggest that triacylglycerols within Schizochytrium sp. oil bodies may be organized in a triple chain-length structure. High-pressure freeze substitution electron micrographs of two other highly unsaturated oil-producing species of microalgae, Thraustochytrium sp. and Isochrysis galbana, also revealed this fine structure, whereas microalgae containing a higher proportion of saturated oil did not. The results suggest that the staining pattern is not an artifact of preparation and that the triple chain-length conformation of triacylglycerols in Schizochytrium sp. oil bodies may be caused by the unique fatty acid composition of the triacylglycerols.

Estimation of Docosahexaenoic Acid Glycerides in Schizochytrium sp. Oil by Open Column Chromatography and Reversed‐phase HPLC

“…The content of DHA (32.94-44.08 %) was much higher than that of DPA (10.84-15.21 %) and EPA (0.77-1.28 %). The ratio of DHA to DPA was 3:1, which was similar to that reported by Ashford et al [24]. Yields of squalene were lower and it was not detectable under some aeration rates.…”

Docosahexaenoic acid production and ultrastructure of the thraustochytrid Aurantiochytrium mangrovei MP2 under high glucose concentrations

“…1. The cells of Aurantiochytrium mangrovei MP2 were separated into two layers after centrifugation at 3500 rpm for 10 min (grown at 8% glucose concentration) acids (Weete et al 1997;Ashford et al 2000;Morita et al 2006). These structures may also be indicative of secondary structure in the triacylglycerols (Ashford et al 2000), but they became indistinct during lipid body enlargement (Weete et al 1997).…”

Biomass production, proximate composition and fatty acid profile of the local marine thraustochytrid isolate,Schizochytriumsp. LEY7 using low-cost substrates at optimum culture conditions

“…Schizochytrium sp. (ATCC 20888) also produced DHA (32.9% TFA) and palmitic acid (25.1% TFA) in high amounts (Ashford, Barclay, Weaver, Giddings & Zeller ). Leaño et al .…”