Isolation, Identification and Fermentation Characteristics of γ-aminobutyric acid-producing Strains

The bacteria in the yellow rice wine koji of Xiecun were isolated, and a strain N1 which was capable of producing γ-aminobutyric acid (GABA) was quantitatively screened by using the methods of thin layer chromatography and precolumn derivatization high performance liquid chromatography. The morphological observation, physiological and biochemical tests, 16S rDNA sequence analysis and identification of the strain were carried out, and its growth curve was plotted, in order to study the effects of the addition amount of sodium glutamate (L-MSG), fermentation time and temperature on the content of GABA produced by the strain N1. The results showed that the content of GABA in the fermentation broth was 448.6 mg·L^-1 after the initial screening. Combined with the identification of morphology, physiology, biochemistry and molecular biology, the strain was identified as Bacillus subtilis. The strain was in the lag phase from 0 to 4 h after the liquid culture, the exponential phase from 4 to 12 h, the stable phase from 12 to 16 h, and the decline phase after 16 h. The optimum culture conditions for the strain N1 were as follows: fermentation time 72 h, fermentation temperature 36℃, pH value 6, inoculation amount 2%, liquid volume 100 mL, and sodium glutamate 1%. Under these conditions, the content of GABA produced by the strain N1 could reach 583.5 mg·L^-1.