Growth and Nutritional Composition of Eustigmatophyceae Monodus subterraneus and Nannochloropsis oceanica in Autotrophic and Mixotrophic Culture

Abstract

Eicosapentaenoic acid (EPA) produced from marine organisms is widely used in nutraceuticals. Monodus subterraneus and Nannochloropsis oceanica, which are representative freshwater and marine Eustigmatophyceae, respectively, are known to have a high content of protein and lipid, particularly, EPA. In this study, to compare the growth and nutritional composition of M. subterraneus and N. oceanica, they were cultured in autotrophic and mixotrophic conditions with JM and f/2 medium, respectively, at 25 o C. In addition, 80 µmol photons m − 2 s − 1with 24-hour and 12-hour light was provided, with the addition of 2% glucose to the medium for the mixotrophic culture. With regard to growth, M. subterraneus showed 10 times higher biomass in a mixotrophic culture than in an autotrophic one. However, no significant difference was observed for N. oceanica between the two culture methods. With respect to nutritional composition, M. subterraneus cultured autotrophically had a higher protein and lipid content, particularly EPA, than that cultured mixotrophically, but no significant difference was found in the two cultures of N. oceanica. Furthermore, M. subterraneus cultured autotrophically with continuous light showed higher nutritional composition, particularly EPA, than N. oceanica. In conclusion, the mass culture of freshwater M. subterraneus is much easier and more economical than marine N. oceanica. In addition, production of EPA will be economically improved if mixotrophic culturing of M. subterraneus is first conducted to maximize the biomass, and then secondary autotrophic culturing is performed.

Expanded utilisation of microalgae in global aquafeeds

“…39 This product is commonly utilised to enrich zooplankton for the feeding of finfish larvae, 92 and they serve as fish oil replacers in feeds for farmed finfish. 40,69,93,94 Some diatom including P. tricornutum can also accumulate EPA ranging from 2.2% to 3.9%, 66 whereas 3% is found in Monodus subterraneus, 95 and 2.8%-4.3% in Nannochloropsis sp., 96,97 indicating their potential viability to partially replace fish oil in aquafeed. However, heterotrophic microalgae, appears to be more promising, owing to their nutritional quality and capacity to be consumed efficiently by the targeted aquaculture species.…”

Current bioeconomical interest in stramenopilic Eustigmatophyceae: a review

“…In this review, the fatty acids found in smaller amounts are not discussed except the mentioning of docosahexaenoic acid (DHA, 22:6n-3) as recorded in the genera Nannochloropsis and Vischeria, and the unusually high content of myristic (14:0) acid (20-54%) in Trachydiscus [66,81,94,114,115,[119][120][121][122][123][124][125]. The general similarity of PUFA composition in both marine and freshwater eustigmatophyceans has led to the suggestion that freshwater species show potential for use in aquacultures [115].…”

Eustigmatophyceae

“…Industrial use of other genera of the Eustigmatophyceae has been investigated to a lesser extent. Monodopsis subterranea (= Monodus subterraneus) and Trachydiscus minutus both produce large quantities of EPA (Cohen 1994;Hu et al 1997;Qiang et al 1997;Lu et al 2001;Iliev et al 2010;Řezanka et al 2010;Cepák et al 2014;Jo and Hur 2015). Members of the closely related genera Vischeria and Eustigmatos have also been noted for producing EPA, but also high amounts of β-carotene, and their lipid metabolism also make them promising biofuels producers (Volkman et al 1999;Li et al 2012a, b;Aburai et al 2013;Zhang et al 2013;Gao et al 2016).…”