Evaluation of the Effect of Agitation Speed on the Growth and High‐value LC‐PUFA Formation of Porphyridium Cruentum Based on Basic Rheological Analysis

ABSTRACTBACKGROUNDThe selection of hydrodynamic properties of microalgae such as agitation speed is usually done according to empirical values without a technical basis, and the selected agitation speeds are not consistent with each other in many references. In this study, we aimed to provide a possible technical basis for the setup of the agitation speed of microalgae suspensions based on basic rheological analysis, in terms of viscosity of microalgae suspensions at different agitation speeds, using the red microalga Porphyridium cruentum as a model.RESULTSThe agitation speed of 150 rpm was optimal for P. cruentum cultivation, with its biomass concentration increased by about 19–57% compared with the microalgae cultured at other agitation speeds. Meanwhile, the content of linoleic acid, arachidonic acid and total fatty acids increased by maximum 103%, 58% and 48%, respectively, compared with those at other agitation speeds. Furthermore, a low rotational speed was beneficial for eicosapentaenoic acid formation (which increased by 72–106%).CONCLUSIONBasic rheological analysis of microalgal suspensions can be used as a guide in setting a reasonable and suitable agitation speed. Meanwhile, the agitation speed could affect both the biomass growth and the formation of certain high‐value products of microalgae. © 2019 Society of Chemical Industry