title: Characterization of soybean protein hydrolysates able to promote the proliferation of Streptococcus thermophilus ST.
abstract: How soybean protein hydrolysates (SPHs) to favor the growth of S. thermophilus ST were investigated. Hydrolyzed soybean protein was fractionated to 4 fragments, that is, SPH-I, SPH-II, SPH-III, and SPH-IV according to their molecular weight sizes. SPHs can improve the growth of strain ST, in which SPH-IV, with the molecular weight of less than 5 kD, significantly promoted the growth of strain ST. The cell counts of strain ST grew quickly from 7.71 to 9.78 (log CFU/mL) when the concentrations of SPH-IV ranging from 0% to 1%. Moreover, 2 chemically defined media (CDMs) were used to test their roles in maintaining the viability of strain ST. CDMs only maintained the survival of strain ST, but SPH-IV had the promotional effects on proliferation of the bacteria. SPH-IV was further characterized to be oligopeptides that contain 2 to 8 amino acids and free amino acids by high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis. The amino acid compositions showed that SPH-IV contained more essential amino acids, which were necessary for the growth of S. thermophilus ST. Clearly, SPH-IV could be used as an exogenous nitrogen supplement to enhance the proliferation of S. thermophilus ST and other lactic acid bacteria, and the data from small scale-up fermentation also supported this point.
authors.affiliation: College of Biological Science & Biotechnology, Beijing Forestry University, Beijing, China.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Hongfei
authors.forename: Bai
authors.initials: B
authors.lastname: Fengling
authors.forename: Zhou
authors.initials: Z
authors.lastname: Fang
authors.forename: Piotr
authors.initials: P
authors.lastname: Walczak
authors.forename: Jiang
authors.initials: J
authors.lastname: Xiangning
authors.forename: Zhang
authors.initials: Z
authors.lastname: Bolin
mesh_terms: D000601:Amino Acids, Essential / Q000032:analysis / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects*; D015169:Colony Count, Microbial; D005285:Fermentation; D005516:Food Microbiology; D008970:Molecular Weight; D011492:Protein Hydrolysates / Q000378:metabolism*; D030262:Soybean Proteins / Q000494:pharmacology*; D048249:Streptococcus thermophilus / Q000187:drug effects* / Q000254:growth & development*
chemical_list: D000601:Amino Acids, Essential; D011492:Protein Hydrolysates; D030262:Soybean Proteins