Ormosil Hybrid Coatings as a Sustainable Antibiofouling Solution for Microalgae Cultivation in Tubular Photobioreactors

Abstract

This study demonstrated the potential of citric acid-APTES (Ormosil) coatings as an effective antifouling strategy to reduce biofilm formation in tubular photobioreactors used for microalgae cultivation. Among the tested coatings, CApTES2.7 exhibited superhydrophilic behavior in air and superoleophobic behavior underwater, significantly reducing the adhesion of Chlorella vulgaris compared to uncoated glass surfaces. Light transmission experiments and microscopic analyses showed that biofilm accumulation on coated surfaces decreased by more than 50 %, maintaining optical clarity within the reactor. Thermodynamic, DLVO, and XDLVO modeling supported these findings, indicating lower adhesion energies for algal cells on Ormosil-coated surfaces, consistent with their experimental antifouling performance. The application of CApTES2.7 coating in tubular PBR systems resulted in a 54.5 % increase in light transmittance compared to uncoated systems, thereby improving the photonic environment available for microalgal growth. Additionally, no chemical cleaning was required between cultivation cycles in coated reactors, demonstrating potential for reducing operational costs and water consumption in large-scale systems. In conclusion, this study presents an environmentally friendly and sustainable approach to overcoming biofilm-induced light attenuation-one of the main bottlenecks in industrial photobioreactors. Ormosil-based coatings not only extend the service life of PBRs but also enhance the economic feasibility of microalgae-based bioprocesses for biofuel, bioplastics, and high-value biomolecule production.