Effects of Peptidase Treatment on Properties of Yeast Protein as an Alternative Protein Source

Abstract

Yeast protein, high-quality and high-content microbial protein, can serve as alternative sources of protein. This study examined the structural and functional characteristics of yeast protein through enzymatic treatment using different ratios of alcalase (endo-type) and prozyme 2000P (exo-type) including 2:1 (A2P1), 1:1 (A1P1), and 1:2 (A1P2). After enzymatic hydrolysis, a significant increase in protein solubility from less than 3.1% in untreated proteins to around 16%, particularly at pH 2 or pH 12. Furthermore, a maximum degree of hydrolysis of over 85% was achieved after enzyme treatment. Among them, the highest value of 87.73% was achieved at yeast protein treated by A1P2. Scanning electron microscopy images revealed varied surface morphologies, with exhibiting an increased surface area, particularly after treatment using A2P1. Next, yeast protein treated with A2P1 also demonstrated a superior emulsion stability index (3364.17). However, the antioxidant capacity was higher in proteins treated with A1P2 (78.30%). In addition, the elevated levels of certain amino acids, specifically leucine, lysine, phenylalanine, valine, and arginine, thereby indicating an enhanced amino acid profile was observed. Overall, yeast proteins treated with complex enzymes exhibited improved functionality and potential for diverse food applications.

Keywords: Yeast protein hydrolysates; alternative protein; endotype protease; exotype protease; hydrolysis.

Fig. 1. Enzyme hydrolysis of yeast protein.

(A) protein solubility, (B) degree of hydrolysis. Different letters indicate statistically significant differences (p ≤ 0.05).

Fig. 2. SDS-PAGE patterns with enzyme hydrolysis of yeast protein.

Fig. 3. Scanning electron microscopic images of yeast protein treated with various ratio of enzyme.

Fig. 4. Fourier transform infrared analysis with yeast protein treated by enzyme hydrolysis.

Fig. 5. UV-spectra scanning of yeast protein treated with complex enzymes.

Fig. 6. (A) Water holding capacity, (B) oil binding capacity, (C) protein surface hydrophobicity, (D) emulsifying activity index, (E) emulsion stability index, and (F) the capacity of radical scavenging on ABTS of yeast protein treated with complex enzyme.

Different letters indicate statistically significant differences (p ≤ 0.05).