Releasing polysaccharide and protein from yeast cells by ultrasound: selectivity and effects of processing parameters.

A 20 kHz high-intensity ultrasound was employed for the selective release of polysaccharide and protein from yeast cells. While the release of polysaccharide and protein was affected by most of the processing parameters, the release selectivity, which is the ratio of the amount of polysaccharide released to that of protein, designated as T/P value, was only influenced by sonication time, temperature and ionic strength, among which temperature had the greatest influence. The T/P value at 85 °C was a factor of 9.3 of the one at 25 °C. The underlying mechanism of this selectivity is speculated to be thermal denaturation and aggregation of protein within yeast cells at elevated temperatures leading to the decrease of protein release by ultrasound. This finding may be useful in exploring a novel selective process for producing polysaccharide and protein fractions from yeast biomass.