Mitigating microalgal biofouling through nutrient regulation and transparent antifouling surfaces while enhancing...

The growing demand for microalgae-derived products, driven by their antioxidant capacity and high value functional compounds, is intensifying the need for more efficient and durable cultivation systems. However, biofouling remains a critical bottleneck, reducing productivity and increasing operational costs in photobioreactors. Although several antifouling solutions have been proposed, most are opaque and therefore incompatible with light-dependent microalgal processes. In this work, the antifouling performance of two novel transparent materials was evaluated using four species of industrially relevant microalgae: Arthrospira platensis, Tetraselmis chuii, Chlorella sorokiniana, and Haematococcus pluvialis. Their performance was benchmarked against conventional substrates (glass and PMMA) and established coatings, including PDMS and the commercial opaque Hempasil X3®. A sequential experimental approach was adopted. First, the influence of culture media and the N / P molar ratio on biomass productivity and cell adhesion was evaluated to identify representative cultivation conditions. Subsequently, transparent antifouling surfaces were assessed under prolonged culture conditions using the selected nutrient conditions. The results demonstrate that the developed transparent surfaces (with a PEG/PDMS-based coating and PMMA-based rigid material) significantly reduce cell adhesion and protein accumulation under biofouling-promoting conditions, reaching values close to commercial antifouling coatings. Cell adhesion was strongly species-dependent, with C. sorokiniana and H. pluvialis exhibiting the highest adhesion. These materials reduced microalgal adhesion by 45-74 % compared to conventional transparent materials such as PMMA and glass while maintaining high optical transparency within the visible range. Therefore, these transparent materials emerge as a promising strategy to enhance the efficiency, stability, and longevity of microalgae cultivation systems.