Accumulation of γ-aminobutyric acid by Enterococcus avium 9184 in scallop solution in a two-stage fermentation strategy.

In this study, a new bacterial strain having a high ability to produce γ-aminobutyric acid (GABA) was isolated from naturally fermented scallop solution and was identified as Enterococcus avium. To the best of our knowledge, this is the first study to prove that E. avium possesses glutamate decarboxylase activity. The strain was then mutagenized with UV radiation and was designated as E. avium 9184. Scallop solution was used as the culture medium to produce GABA. A two-stage fermentation strategy was applied to accumulate GABA. In the first stage, cell growth was regulated. Optimum conditions for cell growth were pH, 6.5; temperature, 37°C; and glucose concentration, 10 g·L(-1) . This produced a maximum dry cell mass of 2.10 g·L(-1) . In the second stage, GABA formation was regulated. GABA concentration reached 3.71 g·L(-1) at 96 h pH 6.0, 37°C and initial l-monosodium glutamate concentration of 10 g·L(-1) . Thus, compared with traditional one-stage fermentation, the two-stage fermentation significantly increased GABA accumulation. These results provide preliminary data to produce GABA using E. avium and also provide a new approach to process and utilize shellfish.