Non-disruptive sonication of A. fusiformis (A. platensis) cultures facilitates its harvesting

•Ultrasound treatment suppresses the buoyancy of A. fusiformis (A. platensis) without affecting the cell viability.•We hypothesize that sonication collapses the gas vacuoles allowing the use of sedimentation as a first harvesting step.•Ultrasound treatment facilitates microalgae harvesting of A. fusiformis.•Biomass concentration was increased about 30 times and microalgae recovery yields of 80–85%.

The cyanobacterium Arthrospira fusiformis (also called Arthrospira platensis) is commercially produced as a human dietary supplement as well as a feed supplement for the poultry and aquaculture industries. Due to the relatively dilute nature of the cultures, cost effective means of cell separation are needed. In this short note we present the use of ultrasounds for buoyancy elimination in A. fusiformis without affecting either its viability or breaking its typical multicellular spiral morphology. We also show how after a non-disruptive sonication treatment, these microalgae can be easily settled thus concentrating the biomass about 30-fold while achieving recovery yields of around 80–85%.