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

• Selectivity in ultrasonic release of yeast polysaccharide and protein was studied.
• Selectivity at 85 °C was a factor of 9.3 of the one at 25 °C.
• The mechanism is speculated to be thermal coagulation of protein within yeast cell.
• The finding may be useful in selectively production of yeast fractions.

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.