Isolation And Application Of Lactobacillus Plantarum SG-5 With High ?-Aminobutyric Acid-Producing

?-aminobutyric acid?GABA?is a non-protein amino acid which is considered a bioactive component known for its physiological functions,including regulating blood pressure,romoting mental stability and brain blood flow.As a new resource food,it had been used in food and pharmaceutical industry.In this paper,a lactobacillus producing GABA was isolated and purified by the met hod of dissolving calcium ring.The properties of the stra in were identified by API CHL50biochemical system and 16S rDNA sequence analysis method.The study on the fermentation product GABA,functional utilization and other biological activity was carried out.The main results are as follows:1.A strain of Lactobacillus plantarum SG-5 with production of GABA was isolated and selected from the source of fermented mulberry leaves.Five target strains were screened and cultured in TYG medium containing 2%Glu.A high yield GABA strain was gained finally by screened 5 target strains.According to content of GABA production,which belongs to Lactobacillus plantarum by analyzing the morphological character,the API CHL50 biochemical system and the 16S rDNA sequence,named for SG-5.The level of SG-5 strain was evaluated by the limit method of acute toxicity experiment,LD₅₀ was more than 10g/kg,which was non-toxic grade.2.The optimum conditions for GABA production by SG-5 strain were established.The orthogonal design of four factors and three levels was designed on the basis of single factor method.The optimal medium composition are the follow:30g/L Yeast extract,20g/L glucose,5g/L sodium succinate and 5g/L L-Glu;And the optimal fermentation temperature and time were 30?for 48h;the initial pH of culture medium is 6.8,inoculums concentration at 5%?×10⁶CFU/mL?.Under these conditions,the GABA content in SG-5fermentation broth reaches up to 7.24g/L.3.Developed a kind of mulberry-soybean milk riched in GABA.The raw material of mulberry-soybean milk were mulberry leaves superfine powder,soy flour and glutamic acid,and SG-5 was fermentation strain.The product was pale yellow and had high quality with exquisite texture,suitable sweet-sour,mulberry leaves fragrance,bean flavor and lactic acid fermentation unique flavor.Preparation conditions:12.5g of soy flour,0.5g of glucose and0.025g of glutamic acid were dissolved in 100mL of mulberry juice,homogenizer mixing and sterilized cooling inoculated of 5%SG-5(×10⁶CFU/mLviable,fermentation for 7h at30?and frozen for 12h²4h at 4?.The end product is mulberry-soybean milk.The main nutrient components were:274kJ of energy,41.5g/kg of protein,18.0g/kg of fat,266mg/kg of sodium,8.2mg/kg of iron,205mg/kg of calcium,4.57mg/kg of zinc,191.4mg/kg of total free amino acid.O n the other hand,coliform was less than 3.0MPN/g,mold and yeast count were<10CFU/g,and Salmonella did not be detected.Functional characteristics:mulberry-soybean milk in the GABA content of 7.25mg/g,and the ACE inhibitory rate?The effects in reducing blood pressure?of mulberry-soybean milk food is 90%in vitro.The physical,chemical and microbial indicators met national standards?GB4646-1999?requirements.4.Safety evaluation of edible mulberry-soybean milk.The experimental group NIH mice were fed with mulberry-soybean milk according to the body weight ratio of0.5mL/20g,and the control group were treated with the same smount of normal saline.The growth and development of the mice in these two group were observed continuously for 14days.The results showed that the index of feeding,drinking,breathing and excretion of experimental group had no significant differences compared with the control group,also had no abnormalities and no poisoning or death.The lethal dose(LD₅₀)was more than0.5mL/20g,which met the national non-toxic standard?GB15193.3-2014?.The heart index of the mice was 0.55%⁰.76%,the liver index was 4.93%⁵.71%,the spleen index was0.42%⁰.62%,the renal index was 1.36%¹.73%,and the difference was not obvious?P>0.05?compared with the control group.The activities of MDA,GST,GPT and GOT were significantly lower than control group?P>0.05?,which showed that the mulberry-soybean milk did not cause any organs and liver function damage in mouse,food is safe.