Optimized Production of GABA and γ-PGA in a Turmeric and Roasted Soybean Mixture Co-fermented by Bacillus subtilis and Lactobacillus plantarum

Abstract

A turmeric and roasted soybean flour mixture (TRSF) was successfully fermented in solid-state using Bacillus subtilis HA and Lactobacillus plantarum K154. The co-fermentation was optimized using the turmeric mixture (turmeric: RSF=1:1), 5% MSG, and a 2-fold volume of water. The TRSF fermented by B. subtilis HA showed a consistency of 1.23 Pa.sⁿ and 3.57% (w/w) mucilage. The co-fermented TRSF exhibited pH 5.94 and 1.94% acidity after the second lactic acid fermentation. The viable cell counts of Bacillus sp. and Lactobacillus sp. were 4.50 × 10⁷ CFU/g and 8.00×10⁹ CFU/g, respectively. In addition, the co-fermented TRSF exhibited a higher GABA content (1.78%) than that of the single strain-fermented TRSF. Serial co-fermentation using two bacterial strains can thus provide novel turmeric-based ingredients fortified with γ-PGA, GABA, peptides, and probiotics.