Abstract: The production of soy peptides by soy meal microorganism fermentation was studied with 30L fermentor. The degree of hydrolysis (DH) increased as the fermentation time prolonged and reached more than 30% at the later stage of fermentation. The content of peptides in fermented liquid first increased and then decreased, so as to indicate that the soy protein was hydrolyzed into peptide and then into free amino acid during fermentation. Enzyme analysis showed that Bacillus subtilis SHZ3 can secrete both protease and carboxypeptidase, which can hydrolyze soy protein and cut down hydrophobic amino acids from the terminus of peptide respectively, resulting in the production of non-bitterness peptides. Results of gel exclusion chromatogra- phy showed that the peptides in fermented liquid of 24h can mainly be consisted of short chain peptides with 300～1000Da. This distribution size is similar to protein enzymatic hydrolysate of certain bioactivities.

Key words: soy peptides, fermentation, defatted soy meal, Bacillus. subtilis SHZ3