Screening Of High-yield BCAT Strains And Establishment And Application Of Electrochemical Detection Systems

Although fermented meat products had a wide range of flavor substances,3-methyl butyl aldehyde by the catabolism of leucine had an important role in fermented meat products.So the pathway of BCAT were study to increase the content of 3-methyl butyl aldehyde in fermented meat products.In this work,the strains were screened through high BCAT activity for fermented meat products and the electrochemical detection system of BCAT activity was established and verified.And the metabolism of muscle proteins by the strains was studied,leucine catabolism,protein degradation and the formation of flavor compounds was analyzed.The research work were follows:(1)A total of 327 single colonies be isolated and purified from Jinhua ham.16 strains were screened for fermentation meat products by gram positive,enzyme negative and other indicators,3 strains were screened for 3-methyl butyl aldehyde to fit for excellent aroma producing ability.Finally,1 strain was screened by acid producing ability,and the strain was Lactobacillus casei.,according to the growth form,physiological and biochemical identification as well as 16S rDNA.(2)The electrochemical detection system of BCAT was established through the modified glassy carbon electrode by multi-walled carbon nanotubes and chitosan composite solution.The result were followed,the detection is the effect under:25.0?L/mL MWCNT,0.2 g/mL CS,0.2?mol/L NAD+,10 mmol/L leucine,15 mmol/L a-ketoglutarate and 0.1 mmol/L PLP.(3)Effect of different concentrations NADH on MWCNT-CS?GCE electrode was studied.The results showed that the detection system had a good linear relationship with NADH concentration of 1.0-9.0?mol/L,and the linear regression equation was y=0.9797x-2.7576,R2 =0.9995.(4)Comparing electrochemical detection of BCAT system and traditional optical detection methods,the results showed that:the activity of BCAT detected by electrochemical method was consistent with that by optical detection when the substrate concentration is changed under the other same conditions.Therefore,the established electrochemical detection system was applied to the detection of BCAT activity of lactic acid bacteria.(5)The culture conditions of Lactobacillus casei L14 were optimized through electrochemical detection system,under pH 7.0,inoculum amount 3.9 mL,NaCl 2.8%and culture temperature 37?.(6)The effect of Lactobacillus casei L14 on muscle protein extracts was studied.The results showed that he BCAT activity of Lactobacillus casei L14 was higher under the optimized culture conditions,then the produce of 3-methyl butyl aldehyde,3-methyl butanol,3-methyl butyric acid and flavor compounds were higher under the optimized culture conditions during muscle protein degradation by Lactobacillus casei.(7)The content of free amino acids(FAA)in fermentation broth was analyzed,the total amount of FAA was the highest under optimization conditions by Lactobacillus casei L14.