Rotational motion in microalgae cultivation, harvesting and processing: A comprehensive review

Abstract

Microalgal biorefineries depend on hydrodynamic choices that govern light access, gas transfer, biomass recovery, and product release, yet rotational motion as an organizing design variable has not been systematically synthesized across the cultivation, harvesting, and downstream-processing stages. This review evaluates rotational motion as a bounded engineering concept, distinguishing mechanically imposed rotation, rotation-induced secondary flow, and rotation-enabled separation from broader mixing or circulation phenomena. A critical narrative synthesis is presented across mechanically agitated photobioreactors, rotation-dominated flow reactors, rotating algal biofilm systems, centrifugal and rotary harvesting devices, and rotationally intensified extraction units. Rather than ranking heterogeneous reports, the synthesis is built on transferable metrics - light–dark cycling, volumetric mass transfer coefficient ( k_La), mixing time, shear or energy dissipation, solids loading, recovery, and biomass quality. The analysis shows that rotation improves productivity and process integration when matched to strain physiology, product value, and scale, but can increase power demand, heating, fouling, and cell damage when defaulted. A five-step decision framework is therefore proposed to select rotational strategies by process objective, strain and product sensitivity, value and purity, scale and solids loading, and standardized reporting.

Keywords

Microalgae bioprocessing / Rotational motion / Photobioreactor / Biomass harvesting / Biofilm reactor / Bead milling

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