Screening Of Protease High-yield Strain And Its Application In Preparation Of Sesame Polypeptide From Sesame Meal

Sesame polypeptide is composed of sesame protein hydrolysis acquired small molecular peptides,which has strong antioxidant activity in vitro and is easy to be absorbed by the human body.It has the physiological activity of lower cholesterol,lowering blood pressure,antibacterial and regulating immunity.It has a good prospect in the fields of drugs,feed additives,health food and food additives.Microbial fermentation is an effective method to produce sesame polypeptide,microorganism grows and breeds quickly,and easy to control the fermentation conditions,we can improve the production efficiency of polypeptides,greatly reduced the cost of production.The study screened a number of protease producing strains from three sample points: the sesame oil processing plant waste,sesame meal wet compost soil and sesame meal.Optimize the medium composition and shake flask fermentation conditions to improve the protease activity of the strain.Applied the strain to fermented sesame meal and obtained sesame polypeptides,regard the DPPH ·scavenging ability and · OH radical scavenging ability as indicators,compare the antioxidant activity of sesame polypeptide in vitro when single and mixed fermentation.The main contents and results are as follows:(1)Isolate 52 protease-producing strains by plate dilution separation method from three samples: sesame oil processing plant waste,sesame meal composting soil and sesame meal.There are 3 strains have distinctly hydrolyzed loop in the casein plate.Choose the strain with highest protease activity and stably named Y1,identifying its 16 S rDNA and physiological and biochemical identification,the strain was proved as Bacillus amyloliquefaciens,and studied the properties of crude enzyme solution.(2)Optimized the shake flask fermentation conditions of the strain Y1,optimal medium composition were 1.5% soluble starch,0.5% yeast powder,0.5% ammonium sulfate and 0.5% sodium chloride.optimal fermentation conditions as follows:optimum initial pH value 6.5,optimum fermentation temperature 37 ℃,inoculation amount 1.5%,fermentation culture time 72 h.After the above optimization experiment,the protease activity of Bacillus amyloliquefaciens was greatly improved from 57.70 U/mL to 363.57 U/mL,which was improved by nearly 7 times.(3)Applied the Bacillus amyloliquefaciens to ferment sesame meal,and the crude extract of the sesame polypeptide had good antioxidant activity in vitro,the DPPH· scavenging ability were 71.378% and ·OH scavenging ability were 68.43%when fermented at 36 h,the strain could fermented sesame meal to prepare sesame polypeptide.(4)Using Lactobacillus plantarum subsp.Plantarum and Bacillus amyloliquefaciens single and mixed fermented sesame meals to prepared sesame polypeptide,study the antioxidant properties in vitro of its fermentation production,regard the DPPH· scavenging ability and ·OH radical scavenging ability as indicators.The Results showed that the solution of sesame polypeptide at the concentration of9.841mg/mL,11.620mg/mL,14.412mg/mL were extracted from the fermentation broth of Bacillus amyloliquefaciens,Lactobacillus plantarum subsp.Plantarum and the mixed bacteria at 36 h respectively,the DPPH· scavenging ability were 71.378%,77.013%,87.622%,and the ·OH scavenging ability were 68.427%,82.507%,92.46%accordingly.So,sesame polypeptide shows high antioxidant activity,sesame meal is a good raw material for the preparation of antioxidant active peptides.There is more sesame polypeptides with the higher DPPH· and ·OH scavenging ability can be extracted from the fermentation broth of Bacillus amyloliquefaciens.mixed with Lactobacillus plantarum subsp.Plantarum than any other bacterias.