Fortification of Poly-γ-Glutamic Acid and γ-Aminobutyric Acid in Homogenized Hydroponic Ginseng Co-Fermented by Bacillus subtilis HA and Lactobacillus plantarum EJ2014

Homogenized hydroponic ginseng (HG) fortified with poly-γ-glutamic acid (γ-PGA) and γ-aminobutyric acid (GABA) was produced by a two-step fermentation using Bacillus subtilis and Lactobacillus plantarum. For optimized production of bioactive compounds, the precursor monosodium L-glutamate (MSG) as well as nutrients such as glucose and skim milk were added. The homogenized HG was pH 6.93 and had an acidity of 0.08%, and viable cell count of 6.13 log colony-forming unit (CFU)/mL. The first (alkaline) fermentation was performed at 42°C for 2 days in the presence of 5% MSG and 2% glucose. The fermented HG was pH 8.08 and had an acidity of 0.03%, a mucilage of 2.13%, a consistency of 0.79 Pa·s(n), and viable cell count of 8.53 log CFU/mL. For the second (lactic) fermentation, the fermented HG was fortified with 5% skim milk, inoculated with 7.54 log CFU/mL of L. plantarum EJ2014, and was incubated at 30°C for 5 days; the resulting in pH 5.63 and had and acidity of 0.35, and viable cell count of 6.71 log CFU/mL (B. subtilis) and 9.23 log CFU/mL (L. plantarum). Moreover, MSG was completely bio-converted with producing 1.03% GABA. Therefore, novel co-fermentation using B. subtilis HA and L. plantarum EJ2014 fortified HG with functional components including γ-PGA, GABA, peptides, and probiotics.