Sedimentation Rate of Dunaliella salina in Dark Conditions

Microalgae are a source of carbohydrates, proteins and lipids. Thus, they can be considered as raw material to transition from current fossil fuel-based refineries to biorefineries. Microalgae harvesting is considered a major challenge in biomass production. There are several harvesting techniques, but the majority of them are either expensive or not effective. The harvesting method that we propose is sedimentation-induced by light blockage, taking advantage of the motility characteristics of certain microalgae. In this research, the halophilic microalgae Dunaliella salina was selected. Experiments were conducted under light and dark conditions to compare the sedimentation rates. Sedimentation behavior was measured by collecting data on the optical density and cell count under both light and dark conditions. The results showed that, under light conditions, the cell count in the middle of the flask decreased from 1 × 106 cell/mL to 5 × 104 cell/mL after 50 days. Under dark conditions sedimentation took less than 10 days for complete settlement. Leaving Dunaliella salina under dark conditions may constitute a promising harvest method as this provides a high recovery rate and requires low energy.