Biofouling remains a critical bottleneck in closed photobioreactors. This study proposes an integrated strategy combining culture medium harmonization, nitrogen-to‑phosphorus (N/P) ratio optimization, and evaluation of transparent antifouling materials (a PEG/PDMS-based coating and a PMMA-based material) under microalgal cultivation conditions. Five industrially relevant microalgae species were successfully grown in a common N-algal medium, enabling unbiased comparison of adhesion behaviour. Increasing the N/P ratio enhanced biomass and lipid accumulation while reducing extracellular protein release and cell adhesion. Although neither antifouling surface completely prevented attachment, both materials significantly reduced fouling compared to glass (45–62% for the coating and 65–74% for the rigid material), while preserving the optical transparency. Antifouling performance was primarily associated with interfacial hydration behaviour and overall surface physicochemical properties rather than a single optimal surface energy. Overall, the rigid transparent material showed the greatest potential for practical implementation in closed photobioreactors applications. • N-algal medium improves growth and modulates adhesion according to the N/P ratio • Higher protein excretion is associated with greater adhesion and lower biomass • Changes in membrane lipids and proteins increase cell hydrophobicity and adhesion • The PMMA-based material showed the best long-term antifouling efficiency • Antifouling relies on interfacial water stability rather than surface energy minima
Álvarez-Álvarez et al. (Sun,) studied this question.