High production of GABA in Pyrus ussuriensis Maximowicz fruit extract by mixed fermentation of lactic acid bacteria

γ-Aminobutyric acid (GABA) was produced by the sequential fermentation of the fruit extract of Pyrus ussuriensis Maximowicz (PFE) with two strains of lactic acid bacteria. The soluble solid content of the PFE was 5.25 oBrix and it also displayed a high potassium content of 127.6 mg/100 g. The first lactic acid fermentation of PFE was performed with Leuconostoc citreum S5 at 25℃ for 2 days. Subsequently, the second lactic acid fermentation was carried out with the first fermented PFE fortified with 3% monosodium ʟ-glutamate (MSG) by Lacobacillus plantarum EJ2014 at 30℃ for 5 days. During the first fermentation, the pH of the PFE medium decreased from 4.42 to 4.19 and the acidity increased from 0.28% to 1.03%. After the second fermentation, pH was 4.64 and acidity was 1.23%. The viable cell counts of Lc. citreum S5 and L. plantarum EJ2014 were 7.94 log CFU/mL and 9.18 log CFU/mL, respectively. The amount of the reducing sugar in PFE increased during the first fermentation period and was nearly consumed during the 2nd fermentation. Notably, MSG was successfully converted into 1.78% of GABA during the second fermentation. In conclusion, high yield for production of GABA was achieved by a novel mixed fermentation of lactic acid bacteria, which highlights PFE as a functional food material.