Screening Of High-yielding γ-aminobutyric Acid Lactic Acid Bacteria And Research On Fermented Carrot Beverage

Gamma-aminobutyric acid is an inhibitory neurotransmitter with functions such as sedation and sleep aid,lowering blood pressure,treating epilepsy,regulating hormones and anti-cancer.It was listed as a new resource food by the Ministry of Health of my country in 2009.Therefore,it is of great significance to develop functional foods rich in γ-aminobutyric acid.The purpose of this project is to screen out a lactic acid bacterium with high γ-aminobutyric acid production,specific external probiotic properties and good safety performance from kimchi,and to optimize the culture conditions for γ-aminobutyric acid production and research on fermented carrot beverage technology,in order to improve the The production of gamma-aminobutyric acid and get a healthy,nutritious and delicious carrot fermented beverage rich in gamma-aminobutyric acid.The main findings are as follows:(1)Screening and identification of γ-aminobutyric acid-producing lactic acid bacteria: 208 suspected lactic acid bacteria strains were obtained through primary screening,and 26 suspected γ-aminobutyric acid-producing lactic acid bacteria strains were obtained through HPLC re-screening.Observation,Gram staining,physiological and biochemical characteristics research and 16 S r DNA identification,21 edible lactic acid bacteria producing γ-aminobutyric acid were obtained: Limosilactobacillus fermentum(1 strain),Pediococcus pentosaceus(1 strain)and Lactiplantibacillus plantarum(19 strains).(2)In vitro probiotic characteristics and safety evaluation of lactic acid bacteria:The results of acid production ability showed that Lactiplantibacillus plantarum NCU001051 had the highest acid production ability,which was 6.46 g/kg;11 strains had a good survival rate under p H 2.5 for 2 h,which Lactiplantibacillus plantarum NCU001051 had the second survival rate of 76.71%;9 strains had a survival rate of more than 80% under 0.5% bile salt condition for 4 h,of which Lactiplantibacillus plantarum NCU001051 had the fourth survival rate of 84.97%;all strains showed good The self-aggregation ability and surface hydrophobicity of Lactiplantibacillus plantarum NCU001051 were the second in self-agglutination ability,which was61.06%,and the surface hydrophobicity rate of Lactiplantibacillus plantarum NCU001051 was the highest,which was 45.15%.All strains showed gamma hemolysis and were sensitive to most antibiotics.Among the edible lactic acid bacteria,Lactiplantibacillus plantarum NCU001051 had the highest γ-aminobutyric acid production at 0.12 g/L.Considering the γ-aminobutyric acid production and the evaluation results of in vitro probiotic properties,Lactiplantibacillus plantarum NCU001051 was selected for subsequent experiments.(3)Optimization of conditions for the production of γ-aminobutyric acid by Lactiplantibacillus plantarum NCU001051: The fermentation conditions were optimized by single factor and orthogonal experiments,and the optimal fermentation conditions of Lactiplantibacillus plantarum NCU001051 were obtained: fermentation time 36 h,L-glutamic acid Sodium addition 4%(m/m),p H 4.5 and fermentation temperature 37 °C.After the fermentation conditions were optimized,the γ-aminobutyric acid production of Lactiplantibacillus plantarum NCU001051 increased from 0.12 g/L to 1.15 g/L,an increase of 9.6 times.(4)Study on the process of carrot fermented beverage with Lactiplantibacillus plantarum NCU001051: Taking acidity,sensory evaluation and γ-aminobutyric acid production as indicators,the optimal process was obtained through single factor and orthogonal experiments: fermentation time 72 h,L-glutamic acid the amount of sodium added was 0.3%(m/m),the inoculum was 3%(v/v)and the fermentation temperature was 38 °C.The acidity of carrot fermented beverage increased from 2.47 g/kg to 10.11g/kg,the production of γ-aminobutyric acid increased from 0.15 g/L to 0.69 g/L,and the sensory evaluation score increased from 55.18 to 83.77.After fermentation,the content of lactic acid and isobutyric acid increased in carrot beverage,while the content of oxalic acid,citric acid,malic acid,tartaric acid,glucose,fructose and maltose decreased.A total of 60 kinds of 9 types of volatile substances were detected in carrot fermented beverages before and after fermentation,including 8 kinds of alcohols,12 kinds of ketones,4 kinds of esters,2 kinds of acids,8 kinds of aldehydes,8 kinds of heterocycles,3 kinds of sulfides,9 hydrocarbons and 6 other compounds;the contents of volatile substances in carrot fermented beverages were significantly different before and after fermentation,among which the contents of ketones and acids increased after fermentation,while the contents of alcohols,esters,aldehydes The content of alkaloids,heterocyclic compounds,hydrocarbons,sulfides and other compounds decreased after fermentation.After the optimization of the fermentation process,the content of γ-aminobutyric acid in the carrot beverage was significantly increased,and the taste and flavor were also improved,laying a foundation for the industrial production of carrot fermented beverages.In conclusion,in this study,a Lactobacillus plantarum NCU001051 with good in vitro probiotic properties,safe and edible and high γ-aminobutyric acid production was screened from kimchi,and the ability of this strain to produce γ-aminobutyric acid and fermented carrot beverages was determined.The optimal process parameters lay the foundation for its application in health food and other industries.