Quantitative evaluation of the ease of rupture of industrially promising microalgae by high pressure homogenization

The susceptibility to rupture of the microalgae Nannochloropsis sp., Chlorella sp. and Tetraselmis suecica by high pressure homogenization was compared quantitatively to the yeast Saccharomyces cerevisiae. Methods for quantifying cell rupture were investigated including cell counting, turbidity, metabolite release and particle sizing. Cell counting was the only reliable method for quantitative comparisons of all microalgae, with turbidity complicated by agglomeration of cell debris for T. suecica, and measurement of metabolite release affected by degradation occurring for all microalgae after significant rupture. The rupture of all microalgae followed exponential decay as a function of number of passes. The pressure required to achieve rupture of 50% of the cells per pass was determined to be 170, 1070, 1380, and ca. 2000 bar for Tetraselmis sp., Chlorella sp., S. cerevisiae, and Nannochloropsis sp., respectively. These results extend the criteria for selecting microalgae for industrial applications beyond consideration of growth and compositional attributes.