Synergistic microalgal cocultivation: Boosting flocculation, biomass production, and fatty acids profile of Nannochloropsis oculata and Phaeodactylum tricornutum

Abstract

Cocultivation of marine microalgae Nannochloropsis oculata and Phaeodactylum tricornutum enhanced biomass production, lipid accumulation, and flocculation efficiency. The coculture yielded 1.3 g L⁻ 1 biomass with 108.06 mg L⁻ 1 d⁻ 1 productivity, and 40.9 % lipid content, surpassing monocultures. Flocculation efficiency reached 78.82 % after 48 h, 1.75–3.20 times higher than monocultures, primarily due to increased loosely bound extracellular polymeric substances (LB-EPS). However, the extended settling time highlights the need for harvesting process optimization. Fatty acid profiling showed increased saturated (56.94 %), monounsaturated (24.99 %), and polyunsaturated (17.08 %) fatty acids, with notable increases in palmitic, myristic, stearic, and eicosapentaenoic acids. The derived biodiesel met international standards for cetane number, kinematic viscosity, and density. Elevated β-carotene and polyunsaturated fatty acids (PUFA) content suggest potential for functional foods and dietary supplements. This cocultivation strategy proves promising for augmenting biomass and lipid productivities, improving harvesting efficiency, and offering added value in food applications. Future research should focus on reducing harvesting time and scaling up production to enhance its viability for sustainable biodiesel production and functional food development. • Algal coculture increased biomass yield and productivity compared to monocultures. • Lipid content in the coculture reached 40.9 %, higher than both monocultures. • Flocculation efficiency improved significantly in the coculture, reaching 78.82 %. • The biodiesel produced met international standards. • Elevated β carotene and PUFA content suggest potential for food applications.