Usage of residual seeds promotes efficient flocculation of biomass.

Bio-flocculation is a sustainable low-cost harvesting technique for microalgae biomass production; however, it is generally less efficient than chemical flocculants. This study aims to investigate the efficiency of seeds as a bio-flocculant for harvesting biomass. Four extracts from integral and residual (seeds without lipids) biomass of seeds using salt or aqueous solutions were used at four concentrations (100, 200, 300, and 400 ppm). Flocculation efficiency (FE) increased as the pH decreased. The addition of the extracts reduced the pH of the cultures, dispensing pH adjustment after dosing the flocculating agent. Salt extracts exhibited higher flocculation efficiency than aqueous extracts. The highest flocculation efficiency (~ 98%) was obtained using a salt extract of residual biomass of seeds in any concentration varying from 100 to 400 ppm. The predicted values obtained from a data modeling using response surface methodology approached the real values (  = 0.9382), resulting in an adequate optimization of the flocculant concentration of ~ 335 ppm and pH 5.6 for a predicted FE of ~ 106%. The findings of the present study confirmed that the salt extract from residual biomass of seeds is an effective bio-flocculant for biomass harvesting.