Understanding Chlorella vulgaris acclimation strategies on textile supports can improve the operation of biofilm-based systems

The interest in microalgae biofilm-based systems has been increasing lately due to their high potential for biomass production. However, more studies focusing on the first stages of this bioprocess, such as support selection and inoculum properties, which may finally affect biomass productivity, are required. The aim of this study was therefore to assess the impact of support nature and inoculum properties on microalgae biofilms productivity and physiology. Results suggest that physico-chemical properties of the support (micro-texture, hydrophobicity and chemical functional groups) affect the attachment of Chlorella vulgaris. Significant differences in cell-distribution pattern and biofilm structure on polyamide-based (Terrazzo) and Cotton-based fabrics were observed. Compared to Cotton, cells grown on Terrazzo showed higher biomass productivity (3.20-fold), photosynthetic capacity (1.32-fold) and carbohydrate pool (1.36-fold), which may be explained by differences in light availability due to support micro-texture. A high inoculum density, resulted in a lower biofilm growth likely due to a lower light/nutrient availability for the cells. Furthermore, when immobilized on fabrics, cells pre-acclimated to 350 µmol photons m-2 s-1 grew faster than those pre-acclimated to low light (50 µmol photons m-2 s-1), demonstrating the influence of light-history of the inoculum cells on biofilm productivity. Therefore, this work confirmed the importance of support and inoculum properties for biofilm-based systems.