Key Types of Yeast Extraction Enzymes
Yeast cells have a complex structure: their cell walls are mainly composed of β-glucans (30–40%), mannoproteins (30–50%), and small amounts of chitin, while the cytoplasm contains proteins, nucleic acids, and other bioactive substances. Different enzymes target specific components to optimize extraction:
Cell Wall-Degrading Enzymes
These enzymes break down the tough yeast cell wall, allowing intracellular components to be released.
β-Glucanases: Hydrolyze β-1,3 and β-1,6 glucans, the main structural polysaccharides in the cell wall. Examples include endo-β-1,3-glucanase and exo-β-1,3-glucanase.
Mannosidases/Mannanases: Target mannoproteins (mannan chains linked to proteins) in the cell wall, disrupting the integrity of the wall matrix.
Chitinases: Degrade chitin (a minor but critical structural component in the cell wall), further weakening the wall structure.
Proteases
Yeast cells are rich in proteins (40–60% of dry weight). Proteases hydrolyze these proteins into smaller peptides or free amino acids, which enhance the flavor (e.g., umami) and solubility of the yeast extract. Common types include:
Endoproteases: Cleave peptide bonds within protein molecules (e.g., trypsin, papain).
Exoproteases: Break down peptides from the ends to release amino acids (e.g., carboxypeptidases, aminopeptidases).
Nucleases
Nucleic acids (DNA and RNA) in yeast cells can be hydrolyzed by nucleases (e.g., ribonucleases, deoxyribonucleases) into nucleotides or nucleosides. These compounds contribute to the umami taste of yeast extract and have potential health benefits (e.g., supporting immune function).
