A circular approach for the efficient recovery of astaxanthin from Haematococcus pluvialis biomass harvested by flocculation and water reusability.

Flocculation has been proved an efficient method for microalgal biomass harvesting, but some coagulant agents may have adverse effects on microalgae growth, making the reuse of the medium unfeasible. In this study, Haematococcus pluvialis was harvested by different flocculants, and the feasibility of the reuse of the culture medium was evaluated. Results suggested that both inorganics, polyaluminum chloride (PA) and ferric chloride (FC), and organics, extracted from Moringa oleifera seed (MSE) and chitosan (CH) resulted in efficient flocculation - flocculation efficiency above 99 %. However, using PA and FC had adverse effects on the astaxanthin recovery from haematocysts - losses of 58.6 and 73.5 %, respectively. Bioflocculants in the reused medium also had higher growth performance than inorganic ones. Furthermore, bioflocculants in reused medium increase the contents of ß-carotene, astaxanthin, and linolenic acid. This investigation demonstrated that using MSE and CHI for harvesting H. pluvialis enables the water reusability from a flocculated medium.

Usage of Moringa oleifera residual seeds promotes efficient flocculation of Tetradesmus dimorphus 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 Moringa oleifera seeds as a bio-flocculant for harvesting Tetradesmus dimorphus biomass. Four extracts from integral and residual (seeds without lipids) biomass of M. oleifera 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 (r 2 = 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 M. oleifera seeds is an effective bio-flocculant for T. dimorphus biomass harvesting.