The Effect of Tofu Wastewater Media and Salinity Levels on Biomass, Chlorophyll, and Phycocyanin Content of Spirulina platensis. Nur Ida Panca Nugrahini*, Arin Dwi Rachmawati, Sudarma Dita Wijayanti, Fenty Nurtyastuti Eka Pertiwi
Faculty of Agricultural Technology, Universitas Brawijaya, Jalan Veteran, Malang, Indonesia
*Email : idaterbaru[at]ub.ac.id
Abstract
Spirulina platensis is a photosynthetic microalga rich in protein, vitamins, and bioactive pigments such as chlorophyll and phycocyanin, which exhibit antioxidant and antimicrobial properties. This microalga has high potential for development as functional food, dietary supplements, and pharmaceutical raw materials. Its growth is strongly influenced by nutrient availability, particularly nitrogen, phosphorus, and organic carbon. However, conventional culture media are relatively expensive for large-scale production. Tofu wastewater, which is nutrient-rich, offers a more economical and environmentally friendly alternative. Previous studies have reported that concentrations of 6-10% tofu wastewater can support S. platensis growth, while salinity (10-30 ppt) also significantly affects growth and metabolism. Yet, limited studies have evaluated the interaction of media type and salinity. This study applied a Completely Randomized Design with two factors: media type (KW21 0.1%, tofu wastewater 10%, and KW21 0.05% + tofu wastewater 5%) and salinity (10, 15, and 20 ppt). Parameters observed included optical density (OD), dry weight, chlorophyll, phycocyanin, protein, and carbohydrate content. Results showed that M1S2 (KW21 0.1%, 15 ppt) achieved the highest OD (0.454), protein (124.43 mg/L), and carbohydrate (217.54 mg/L), while M2S2 (tofu wastewater 10%, 15 ppt) produced the highest biomass (3133.3 mg/L). Although KW21 medium gave the best performance, tofu wastewater remains a promising sustainable alternative for microalgae cultivation.
