To break up microalgal cells with the least possible damage to organelles etc. I used to force the suspension through a fine needle under high pressure. This way you can adjust the intensity of the treatment by varying pressure, diameter, and length of the needle easily to the result you want.
The advantage of this technique is that all cells are treated in a very similar way as compared to sonication, mortar, or any other disruption technique that acts on a volume. due to turbulence nad dead spaces much more variability occurs there.
High pressure, in combination with tubing and needles, is dangerous to work with, so construction must be professional and well thought out.
The disadvantage is that you have to adjust the setup separately for each kind of cells, using microscopic control of the result: no intact cells at a minimum intensity of the treatment.
A low-pressure variation can be used to separate colonial forms into single, surviving cells.