Of Gaba-producing Lactic Acid Bacteria Strain And The Optimum Fermentation Conditions

γ- Amino butyric acid (GABA) is a kind of non-protein amino acid in nature, It is an important inhibitory neurotransmitter of the mammals'central nervous system. It can participate in cerebral circulation and influence on depressing blood-pressure, improve functions of brains, enhance memorial ability, resist anxiety and other biological functions. GABA is also a functional factor in medicine, food and can be found widely in natural environment. It presents in animals, plants and microorganisms. Because the content of GABA in animals and plants is lower and difficultly to extract, the microorganisms are the main sources of GABA. Some strains like lactic acid bacteria, molds and yeasts are mainly used to produce GABA. In this research, the high yields GABA- producing lactic acid bacteria was selected and cultivated and the conditions of GABA fermentation was optimized.Six preserved lactic acid bacteria were carried on amino acid analysis, a GABA-productive strain, Lactobacillus brevis HDBR-02, was obtained and its yield of GABA was 0.21mmol/L. A highly GABA-producing mutant F11 has been acquired after the UV mutagenesis, the NTG mutagenesis and the UV&NTG mutagenesis. The GABA yield detected quantitatively by HPLC was 0.87mmol/L, which was four times than the original yields. The best dosage of mutagenesis was: The irradiation time of ultraviolet was 13s, 24cm. concentration of NTG was 0.6 mg/mL, mutagenic processing time was 30min. The genetic characteristics were stabile after 10 successive generations of F11. For higher GABA yields, the optimal fermentation conditions of F11 had been studied. After the optimized of glucose,the yeast extract,the peptone and original pH value in the primary GYP fermentation medium by single factor experiments and orthogonal experiments, the conclusion was obtained that the best amounts(g/L) of fermentation medium was: The glucose 10, the yeast extract 20, the peptone 5, the anhydrous Sodium Acetate 2, MgSO₄·7H₂O 0.02, MnSO₄·4H₂O 0.001, NaCl 0.001, FeSO₄·7 H₂O 0.001, pH 6.0, glutamate Sodium content was 5%, And the optimal temperature was 30℃, the best fermentation time was for 3 days, cultured statically. Under this condition, the GABA yield of F11 was 1.19mmol/L, which is 6 times than that of the original strain HDBR-02.