the second group with compact smooth pellets in which the whole pellet is compact and the outside of the pellet is smooth;
the last group with hollow smooth pellets in which the centre of the pellet is hollow due to autolysis and the outside is smooth (Metz and Kossen, 1977).
The pellets were separated from the media and the wet-weight of the pellets were determined prior to harvesting of the microalgae biomass.It was reported that more compact pellets will are advantageous for subsequent cell harvesting (Olaizola, 2003; Zhang and Hu,2012).