Background Scenedesmus species can synthesize beneficial nutrients such as protein and lipids, which exert positive effects on the growth and disease resistance of aquatic animals. However, photoautotrophic cultivation of Scenedesmus species currently suffers from low biomass and target product yields. Therefore, it is essential to ascertain the optimal cultivation mode for maximizing biomass accumulation and target product synthesis efficiency.

Objective This study aimed to screen suitable cultivation methods for efficient growth and high-value nutritional component synthesis of Scenedesmus species, facilitating its development and application in aquatic feeds. Taking S. bijugus SS-303 as the experimental material, we systematically compared the effects of photoautotrophy, heterotrophy and mixotrophy on its growth performance, nutrient consumption and biochemical composition.

Results The algal strain was identified as S. bijugus via ITS molecular identification. Microalga by the mixotrophic mode achieved a biomassof 18.98 g/L (dry weight) that was significantly higher than the heterotrophic group (12.95 g/L) and photoautotrophic group (1.25 g/L), with larger cell size. It could fully utilize glucose and urea, showing the highest nutrient utilization efficiency. In terms of nutritional components, the contents of protein (41.46%), essential amino acids (16.92%) and total amino acids (34.88%) in the mixotrophic group were remarkably higher than those in the other two groups. No significant difference was observed in lipid content among the three groups. The photoautotrophic group had the highest content of α-linolenic acid (C18:3ω-3, ALA), while the heterotrophic group had the highest proportion of linoleic acid (C18:2ω-6, LA). Carotenoid contents in photoautotrophic and mixotrophic groups were significantly higher than those in the heterotrophic group. Compared with previously reported algal strains, S. bijugus SS-303 presented high yields of biomass, protein, lipids, essential fatty acids and amino acids under mixotrophic culture conditions.

Conclusion  Mixotrophy is the optimal cultivation method for S. bijugus SS-303, which can simultaneously achieve high biomass production and synthesis of high-quality nutritional component This findings provide theoretical basis and technical support for the high-value utilization of this alga in aquaculture industry.