Fermented Milk Product Enriched with γ-PGA, Peptides and GABA by Novel Co-Fermentation with IBacillus subtilis/I and ILactiplantibacillus plantarum/I

• Published in: Fermentation (Basel) Vol. 8; no. 8
• Main Authors: Lee, Sam-Pin, Yoon, Woong-Kyu, Lee, Jinho, Garcia, Coralia V
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.08.2022
• Subjects: Bacillus subtilis; Fermented milk; GABA; Identification and classification; Nutritional aspects; Peptides; South Korea
• ISSN: 2311-5637; 2311-5637
• DOI: 10.3390/fermentation8080404

Milk was co-fermented with Bacillus subtilis HA and Lactiplantibacillus plantarum EJ2014 to produce a dairy ingredient enriched with poly-γ-glutamic acid (γ-PGA) and γ-aminobutyric acid (GABA). The first fermentation of milk with B. subtilis HA resulted in a viscous broth with pH 6.56, 0.26% acidity, 1.40 mg/g tyrosine equivalent, and 17.21 U/g protease activity. The viable cell counts of B. subtilis indicated 8.74 log CFU/mL, and the consistency index of the alkaline fermented milk was 1.82 Pa·s[sup.n] . In addition, 4.65% mucilage was produced with 35.93% γ-PGA content. The milk co-fermented by L. plantarum indicated 1.34% acidity and pH 4.91. The viable bacterial counts of B. subtilis decreased to 4.44 log CFU/mL, whereas those of L. plantarum increased to 9.42 log CFU/mL. Monosodium glutamate (MSG) as a precursor was effectively converted into γ-PGA by B. subtilis, and then residual MSG was completely converted into GABA by L. plantarum with a yield of 26.15 mg/g. Furthermore, the co-fermented milk produced volatiles, including hexanoic acid, 2,3-butanediol, and acetoin, which may be responsible for its aged cheese-like aroma.