Higher production of GABA by co-fermentation lactic acid bacteria with R. verniciflura extract. The pH and acidity of the RV extract were 4.49 and 0.13%, respectively. The soluble solid and polyphenol contents were 0.52% and 5.77 mg/g, and the reducing sugar content was 3.9 mg/g. The RV extract (15%, v/v) was mixed with sucrose (5%) and yeast extract (1%). The mixture was fermented for 2 days at 25℃ in the presence of Leuconostoc citreum S5. The second fermentation step involved the use of, Monosodium glutamate (5%, precursor) and skimmed milk (5%). The second fermentation was carried out by Lactobacillus plantarum EJ2014 at 30℃ over a period of 7 days. The pH of the co-fermented RV extract was 4.75 and the acidity was 0.99%. The viable bacterial count for Leuc. citreum S5 and L. plantarum EJ2014 were 4.10 log CFU/mL and 8.68 log CFU/mL, respectively. The complete bio-conversion of MSG produced GABA (24.56 mg/mL). The 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (ABTS) radical scavenging activity of the co-fermented RV decreased (from 3.89 mg/mL to 2.03 mg/mL (IC 50 values) for DPPH; from 16.03 mg/mL to 5.07 mg/mL (IC 50 values) for ABTS). In conclusion the novel co-fermentation of RV extract could provide multi-functional ingredients, including GABA and probiotics.