The effects of trophic mode and medium composition on the biochemical profile and antioxidant capacity of Tetraselmis chuii (CCAP 66/21B)

Microalgal cultivation influences the bioaccumulation of high-value compounds such as omega-3 (ω-3) fatty acids and carotenoid pigments. Therefore, cultivation optimisation is essential to upregulate high-value compound yields. The present study investigated the effects of trophic mode (autotrophy, heterotrophy and mixotrophy) and media composition on the biochemical make-up, pigment signature, fatty acid profile, and antioxidant capacity of the marine chlorophyte, Tetraselmis chuii (CCAP 66/21 B). The 13 conditions significantly affected the biochemical profile of T. chuii (CCAP 66/21 B) with high variation in carbohydrates (78.5–151.7 mg glucose eq g⁻¹dw), lipids (208.3–475.1 mg g⁻¹dw) and soluble proteins (47.3–373.9 mg BSA eq g⁻¹dw). Trophic mode influenced the yields of high-value nutraceutical carotenoids (lutein and β-carotene) with the highest returns observed in photoautotrophic conditions (e.g., 2.51 ± 0.11 mg β-car g⁻¹dw and 1.96 ± 0.14 mg lut g⁻¹dw for K medium). Organic supplementation also induced significant shifts in the proportions of polyunsaturated fatty acids (ω-3 and ω-6 PUFAs), monounsaturated fatty acids (MUFAs) and saturated fatty acids (SFAs). Here, heterotrophy and mixotrophy significantly upregulated MUFA content (33.2 ± 4.0%) and SFA content (31.29 ± 0.9%), respectively. Moreover, mixotrophy significantly enhanced biomass yield (6.3-fold), soluble protein content (3.9-fold) and the antioxidant capacity (5.2-fold) of T. chuii (CCAP 66/21 B) compared to obligate photoautotrophy and heterotrophy. As such, trophic mode is a principal growth parameter that can modulate the content of T. chuii (CCAP 66/21 B) for potential downstream applications such as biofuels, pharmaceuticals, nutracurticals or aquaculture probiotics.