Enhancing structure, functionality, in vitro digestibility and bioactivity of yeast protein by pH-shifting assisted ultrasonication treatment.

Yeast is a promising source of alternative protein, but the low functionality limits the application of yeast protein in food industry. This paper demonstrated pH-shifting assisted ultrasonication treatment could significantly enhance the solubility of yeast protein from Kluyveromyces marxianus, with protein recovery rate increased from 7.32 % to 81.59 % at pH 12, 900 W for 120 min (pH 12-U900), and with the significant occurrence of higher-molecular-weight yeast proteins as witnessed by SDS-PAGE and SEC. The subsequent acid precipitation resulted in yeast protein with high protein content, increased hydrophobicity and higher disulfide bonds content. pH-shifting assisted ultrasonication increased the relative abundance of 60S/40S ribosomal protein, glycolytic enzymes and elongation factor revealed by proteomic analysis; and significantly improved protein functionality including higher solubility, emulsifying activity, foaming capacity, and superior oil holding capacity. Moreover, the prepared yeast protein was found to be rich in essential amino acids and had a high in vitro gastrointestinal digestibility. Peptidomics characterization further suggested the abundant proteins in yeast could release potentially bioactive peptides, especially with better ACE inhibitory activity (IC50 of 0.92 mg/mL). This study demonstrated pH-shifting assisted ultrasonication could be an effective approach to improve yeast protein and supplied a theoretical basis for better development as an alternative protein.