Alleviating Effect Of Lactobacillus Plantarum D-9 On Depression Like Behavior In Mice And Its Application

Depression is a common central nervous system disorder that has a great impact on people’s health and life.γ-aminobutyric acid is an inhibitory neurotransmitter that may have some alleviating effects on depression.In this study,we revealed the alleviating effect and mechanism of a strain of Lactobacillus plantarum D-9,which can produceγ-aminobutyric acid,on depression-like behavior in model mice through the establishment of a depression animal model,behavioral assessment,evaluation of relevant antidepressant biomarkers in vivo,and high-throughput sequencing.Subsequently,the fermentation process of Lactobacillus plantarum D-9 on fermented red raspberry juice was optimized,and a lactic acid bacteria fermented red raspberry beverage with good taste was produced.In this study,the conditions for the preparation of Lactobacillus plantarum D-9bacteriophage were firstly optimized.The results showed that the optimum medium for Lactobacillus plantarum D-9 was 2.9%glucose,3.1%yeast paste,0.6%sodium acetate,0.2%diammonium hydrogen citrate and 0.2%dipotassium hydrogen phosphate,and the initial p H was adjusted to 5.5.After fermentation at 37℃for 24 hours,the activity of the final fermentation broth was 1.26×10⁹CFU/m L.The best base protectant for lyophilization was 12%skim milk,and the best mixture of bacterial slurry and protectant was 1:2.Finally,the viable bacteria of the lyophilized powder was 1.95×10¹¹CFU/g.Subsequently,a chronic unpredictable mild stress mouse model was constructed in this study,and the alleviating effects of Lactobacillus plantarum D-9 on depression-like behavior in mice were assessed by behavioral experiments,tryptophan metabolism,inflammatory biomarkers,and intestinal flora.The results of behavioral experiments showed that Lactobacillus plantarum D-9 alleviated weight loss,restored the lack of pleasure caused by modeling,improved exploratory ability and decreased locomotor activity,and increased the pathological characteristics of survival;Lactobacillus plantarum D-9 increased the level ofγ-aminobutyric acid in mice;Lactobacillus plantarum D-9caused tryptophan to proceed toward the pathway of 5-hydroxytryptamine production,reduced tryptophan along the kynurenine Lactobacillus plantarum D-9 inhibited the secretion of pro-inflammatory cytokines and promoted the secretion of anti-inflammatory cytokines to regulate the immune imbalance.The analysis of intestinal flora showed that Lactobacillus plantarum D-9 could regulate the intestinal flora of chronic unpredictable mild stress mice,regulate the relative abundance of immune-related flora,improve the composition of intestinal flora..Finally,in this study,Lactobacillus plantarum D-9 was co-fermented with red raspberry to produce a lactic acid bacteria fermented red raspberry beverage with good taste.The optimal fermentation conditions are:6×10⁵CFU/m L inoculum,10%sugar addition,6h incubation at 39℃.The live bacteria count of the fermented juice can reach 6×10⁴CFU/m L.It meets the requirements of national health standards.After the fermentation of red raspberry juice by lactic acid bacteria,the proportion of irritating aldehydes is reduced,and the proportion of acids and ketones with aromatic odor is increased,so that the taste and flavor are improved and softer.In conclusion,Lactobacillus plantarum D-9 preserved in our laboratory can increase theγ-aminobutyric acid content in mice,regulate the intestinal flora,and regulate the balance of excitation and inhibition in the brain and immune imbalance.The juice obtained by co-fermentation of Lactobacillus plantarum D-9 and red raspberry has good taste and is functional,it shows a good application prospect in food industry.