Enriched Fermented Water Hyacinth Extract as a Low-Cost Medium for Arthrospira platensis: Effects on Growth, Pigments and Cost Efficiency

The development of low-cost culture media is essential for expanding the commercial production of Arthrospira platensis, particularly in regions where conventional synthetic formulations remain economically prohibitive. In this study, an enriched extract derived from fermented water hyacinth (Pontederia crassipes) was evaluated as a 25% substitute for standard Zarrouk’s and m-NRC media under controlled laboratory conditions. Growth performance was monitored through optical density (OD₇₅₀), and biomass productivity, specific growth rate, and doubling time were determined. Pigment composition, including chlorophylls, carotenoids, and phycobiliproteins, was analysed spectrophotometrically. Zarrouk’s medium supported the highest biomass productivity (0.1603 ± 0.006 g L⁻¹ day⁻¹), followed by m-NRC (0.1371 ± 0.005 g L⁻¹ day⁻¹) and 25% EWHE (0.1134 ± 0.0003 g L⁻¹ day⁻¹), while the highest specific growth rate was observed in m-NRC (0.2949 ± 0.0059 day⁻¹). In contrast, the enriched extract significantly enhanced the accumulation of accessory pigments, particularly phycocyanin (3.67 µg mL⁻¹) and allophycocyanin, which are important high-value compounds used in food, nutraceutical, and biotechnological applications. Although chlorophyll and carotenoid contents were higher in Zarrouk’s medium, the EWHE formulation demonstrated advantages for pigment-oriented production. Cost analysis identified EWHE as the most economical medium (₹12.45 L⁻¹). Despite supporting comparatively lower biomass productivity than synthetic media, the enriched water hyacinth extract offers a cost-effective and sustainable alternative for pigment-focused cultivation. This approach highlights the potential of integrating invasive biomass valorisation with microalgal production, contributing to circular bioeconomy strategies.