| As an inhibitory neurotransmitter in the central nervous system,γ-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. |
