Screening And Fermentation Characteristics Of Lactic Acid Bacteria For Producing ?-Aminobutyric Acid

As an inhibitory neurotransmitter in the central nervous system,?-Amino butyric acid(GABA).GABA is a non-protein amino acid with various physiological activities and is widely found in animals and plants.In the human body can play a variety of physiological functions,such as lowering blood pressure,anti-anxiety,improving depression,enhancing memory,improving brain function,and inhibiting asthma.As a variety of physiological activity factors,GABA has become a hot spot in various fields.Nowadays,it has become a hot spot not only in the food industry,but also in the pharmaceutical,animal husbandry,and even cosmetics industries.It has gradually become a hot spot for scientific researchers to meet people's needs for their physiological functions.Years of studies have shown that lactobacillus,as a typical representative of probiotics,can maintain the balance of normal flora in the gastrointestinal tract,reduce serum cholesterol,anti-cancer,anti-aging and other probiotic functions.With the increase of Alzheimer's disease,insomnia,anxiety,depression and other related patients,the probiotic function of GABA has attracted more and more attention of researchers.In this study,a GABA-producing Lactobacillus plantarum D-9 was isolated from traditional fermented foods,and its biological characteristics were studied.The fermentation medium and fermentation conditions were further optimized and the GABA-producing ability was improved.The main contents and results of this paper are as follows:(1)Two hundred and eighteen strains of lactic acid bacteria were isolated from the traditional fermented pickles of Zhejiang families.Qualitative screening and quantitative re-screening of GABA in fermentation broth of isolated strains were carried out by TLC and high performance liquid chromatography.Finally,a strain D-9 with high yield of GABA was screened out,and the yield of GABA was 0.672 g/L.(2)The physiological and biochemical and biomolecular identification of the isolate D-9 was further carried out.The morphological characteristics,individual morphological characteristics and physiological and biochemical tests of the isolate D-9 colonies showed that the isolate D-9 belongs to the genus Lactobacillus.After 16S rDNA molecular biology was further identified at the genetic level,the isolate D-9 was a Lactobacillus plantarum.(3)The physiological characteristics of Lactobacillus plantarum D-9 were studied.The results showed that Lactobacillus plantarum D-9 reached logarithmic growth stage at 12 hours,the optimum culture temperature was 37?,and the optimum culture pH was 6.5,which had strong osmotic pressure resistance.(4)The GABA yield,medium and fermentation conditions of Lactobacillus plantarum D-9 were optimized.Through single factor and orthogonal experiments,the optimal fermentation medium formulation was 1.8%(w/v)yeast extract,1.5%(w/v)glucose,1.5%(w/v)L-glutamate and initial pH was 5.5.The optimum fermentation conditions of Lactobacillus plantarum D-9 were obtained by single factor test and response surface optimization test.The optimum fermentation conditions were inoculation amount of 6%(v/v),fermentation temperature of 31?,fermentation time of 42 h,and the highest GABA yield could reach 1.413 g/L.