Mutation Breeding And Identification Of Lactic Acid Bacteria For γ-aminobutyric Acid Production And Optimization Of Fermentation Conditions

Gamma-aminobutyric acid (GABA) is a kind of natural amino acid of protein, which is an important inhibitory neurotransmitter in the mammalian central nervous system. It has various physiological functions such as calming, ease blood pressure. High-yield GABA strain was screened and the stable mutant strain was obtained by ultraviolet mutagenesis, then determined the optimal medium and fermentation conditions by single-factor and L9 (34) orthogonal test.At last, the strain was identified by 16S rDNA gene sequences.The results are as follows:Four high-yield GABA strains (Sc6-2、18M376、S4-5 and S3-3)was screened out from 80 strains of lactic acid bacteria, which were irradiated to several times with ultraviolet light (each for 60,40,40 and 80 seconds at a distance of 30 cm from the light). A mutant strain US3-3 was obtained and its content of GABA was 2.482g/L, which was 1.9 times as much as original strain. The GABA content of strain US3-3 was maintained the genetic stability after 7 successive passages.The optimal fermentation medium of strain US3-3:the seed medium with 3% of L-glutamic acid sodium,0.4g/L of vitamin B6 and 0.3% calcium chloride. The optimal fermentation conditions:inoculation 4%, initial pH value 5.5,fermentation temperature 37 ℃ ,fermentation time 36h. Under this condition, the content of GABA was 3.094 ± 0.022g/L, which was 1.2 times as much as the control group.The strain US3-3 was identified as Pediococcus acidilactici based on 16S rRNA gene sequences, and the homology of Pediococcus acidilactici EU147310 was 100%.