Enhanced biomass recovery via self-flocculating microalgae: A response surface methodology approach

Despite the benefits of using microalgae-based biofuels as a sustainable alternative to conventional fossil fuels, the high cost of biomass harvesting remains a significant challenge. This study investigates the potential of cocultivating Pleurochrysis carterae as a self-flocculating microalgae for harvesting Chlorella vulgaris . Response Surface Methodology (RSM) was employed to optimize key parameters, including pH, mixing time, settling time, and microalgae ratio, to maximize harvesting efficiency. The results showed that settling time and pH were the most influential factors, with optimized conditions achieving a harvesting efficiency over 90 %. The bioflocculation mechanism was primarily attributed to charge neutralization and the secretion of extracellular polymeric substances (EPS) by P. carterae . Besides improving the harvesting efficiency, cocultivation of P. carterae with C. vulgaris enhanced biomass production and lipid content from 0.740 g/L and 26.17 % in monoculture of C. vulgaris to 1.22 g/L and 33.98 %, respectively. Furthermore, co-cultivation improved nutrient removal efficiency, highlighting its potential in sustainable wastewater treatment. These findings demonstrate that self-flocculating microalgae offer a cost-effective and environmentally friendly solution for microalgae harvesting, addressing a major barrier in biofuel production. This study provides valuable insights into optimizing bioflocculation processes and highlights the advantages of leveraging self-flocculation for efficient microalgae biomass recovery. • Bioflocculation using P. carterae achieved a harvesting efficiency of over 90 %. • Co-cultivation of P. carterae and C. vulgaris increased biomass yield to 1.22 g/L. • Lipid content reached 33.98 % under co-culture conditions. • Charge neutralization and EPS secretion were identified as key mechanisms of flocculation.