Characterization of sulfur-compound metabolism underlying wax-ester fermentation in Euglena gracilis

Abstract

Euglena gracilis is a microalga, which has been used as a model organism for decades. Recent technological advances have enabled mass cultivation of this species for industrial applications such as feedstock in nutritional foods and cosmetics. E. gracilis degrades its storage polysaccharide (paramylon) under hypoxic conditions for energy acquisition by an oxygen-independent process and accumulates high amount of wax-ester as a by-product. Using this sequence of reactions referred to as wax-ester fermentation, E. gracilis is studied for its application in biofuel production. Although the wax-ester production pathway is well characterized, little is known regarding the biochemical reactions underlying the main metabolic route, especially, the existence of an unknown sulfur-compound metabolism implied by the nasty odor generation accompanying the wax-ester fermentation. In this study, we show sulfur-metabolomics of E. gracilis in aerobic and hypoxic conditions, to reveal the biochemical reactions that occur during wax-ester synthesis. Our results helped us in identifying hydrogen sulfide (H2S) as the nasty odor-producing component in wax-ester fermentation. In addition, the results indicate that glutathione and protein degrades during hypoxia, whereas cysteine, methionine, and their metabolites increase in the cells. This indicates that this shift of abundance in sulfur compounds is the cause of H2S synthesis.

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Lipids from Microalgae for Cosmetic Applications

“…Commonly Waxes fall into the fatty ester class, among the fatty acyl category [20]. Euglena gracilis is a microalga that accumulates a high amount of wax-ester as a by-product of the degradation process of storage polysaccharides, useful today for biofuel production but they could also prove helpful in cosmetics [89,117,118]. For example, waxes are key components in lipsticks since they provide appropriate rigidity, hardness, stability, and texture to the stick.…”