Fortification of Mucilage and GABA in Hovenia dulcis Extract by Co-fermentation with Bacillus subtilis HA and Lactobacillus plantarum EJ2014

Abstract

Hovenia dulcis Thunb. extract (HDE) was co-fermented by Bacillus subtilis HA and Lactobacillus plantarum EJ2014. The co-fermentation was optimized by adding glucose (3% for the first fermentation, 1.5% for the second fermentation), MSG (5%), and skim milk (5%). The HDE broth fermented by B. subtilis HA showed pH 7.3, 0.09% acidity, 0.52 mg/g tyrosine equivalents, and viable bacterial counts of 1.4×10⁹ CFU/mL. The viscous broth obtained indicated a consistency index of 3.90 Pa.sⁿ and 32.70 mg/mL mucilage after 2 days. Subsequently, after the second fermentation, the broth indicated pH 4.5, 1.08% acidity, 0.87 mg/g tyrosine equivalents and viable bacterial counts of 2.0×10⁶and 3.0×10⁹ CFU/mL for B. subtilis HA and L. plantarum EJ2014, respectively. The MSG substrate was effectively converted into GABA, which showed a final concentration of 16.08 mg/mL in the broth. Therefore, the co-fermented HDE was effectively fortified with mucilage, GABA, peptides, and probiotics, and could be used as a functional ingredient for nutraceuticals.