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Evaluating microalgal cell disruption upon ultra high pressure homogenization

Bernaerts, Tom M.M., Gheysen, Lore, Foubert, Imogen, Hendrickx, Marc E., Van Loey, Ann M.
Algal research 2019 v.42 pp. 101616
Nannochloropsis, cell membranes, cell walls, fluorescence microscopy, homogenization, microalgae, scanning electron microscopy, turbidity, viability
The impact of (ultra) high pressure homogenization on the degree of cell disruption was investigated for Nannochloropsis sp. suspensions. The degree of cell disruption was studied by combining four evaluation methods: turbidity measurement, scanning electron microscopy, hexane:isopropanol extraction efficiency, and fluorescence microscopy using the viability stain SYTOX green. Applying an ultra high pressure of 250 MPa obviously reduced the number of homogenization passes required to obtain a specific degree of cell disruption compared to 100 MPa. However, heating of the sample occurred at 250 MPa, resulting in extensive aggregate formation of the released intracellular material after multiple homogenization passes. Furthermore, cell wall integrity was not necessarily linked to membrane integrity, implying that moderate (U)HPH conditions are possibly sufficient for certain applications by damaging the cell membrane, without achieving full rupture of the cell wall. Once again it was proven that different methods for evaluation of cell disruption should be combined to get comprehensive insight into the disruption of microalgae.