From Lab to Industry: Optimization and Industrial Application of Microalgae-Based Formulations for Dyeing and Functionalization of Linen Fabrics

Microalgae are promising renewable resources for textile dyeing and functionalization, but their industrial transfer remains limited. This work developed and optimized whole microalgal biomass-based formulations for application onto 100% linen fabric using dip–pad–dry processes compatible with conventional textile finishing lines. Textile substrate screening, binder selection, cross-linker optimization, fixation auxiliary strategy, and guar gum stabilization were sequentially evaluated. Initial binder-only formulations showed poor washing durability, with color strength (K/S) losses of at least 49% after one washing cycle. The optimized formulation, composed of acrylic dispersion, Nannochloropsis gaditana (N. gaditana), cross-linking agent, fixation auxiliary system, and guar gum, improved formulation stability, color retention, and antioxidant performance. Validation with different microalgal species confirmed species-dependent washing durability, with N. gaditana showing the best color retention after 10 washing cycles and being selected for industrial-scale application. The industrially functionalized linen fabric showed excellent rubbing, washing, water, and perspiration fastness, while light fastness remained limited. Garment prototypes produced from the dyed/functionalized fabric confirmed the practical applicability of this approach. These results support the valorization of whole microalgal biomass as a renewable pigment-like functional component for lower-impact textile finishing using industrially compatible aqueous processing.