Screening For Glutaic Acid Decarboxylase-producing Fungi From Tea Plants And Optimizing For Enzyme-producing Conditions

The fungi in tea fermentation are diverse, which are potential resources of many enzymes. But isolated strains which have glutamate decarboxylase activity in tea are not many reports, and with different sources of microbial strains producing GAD is limited. It is necessary to screen more strains to produce GAD.The thesis chooses 21 fungal strains isolated from healthy tea, Pu-erh tea, Fuzhuan tea and six-Pao tea, than by color screening,11 steains fermentation all has a green color response. FZ-3, LB-8 strain are darker than others,than after colorimetric screening, LB-land LB-6 strains' OD637 value are higher than others. Thereby obtaining those strains both better growth conditions and glutamate decarboxylase dynamic:CSN-4, LB-1, LB-6, LB-8. On the basis of bran as enzyme fermentation medium, evaluate the tablet in the oxidase and hydrolase, detecting that in the CSN-4, fermented liquid has 5 kinds of enzyme activity :tannin enzyme, polyphenol oxidase, laccase, cellulase and lipase. LB-1, LB-6, LB-8 were detected cellulase and lipase activity,which proving CSN-4 strain can produce higher species complex enzyme in the bran fermentation medium. In different fermentation medium, after 3 d fermentation, detecting various strains enzyme production situation, UPLC test results showed that the bran as the main component of adding sodium glutamate fermentation enzyme production medium, the highest glutamic acid decarboxylase enzymes, than by response surface optimization, the optimal bran fermentation culture medium formula is:peptone 2.25 g/L, bran 30.0 g/L, potassium dihydrogen phosphate 2.0 g/L, magnesium sulfate 0.2 g/L, manganese sulfate 0.5 g/L, tea 8 g/L.Among them, the inducer monosodium glutamate 8.3 g/L, after the response surface optimization,gamma-aminobutyric acid gose to 2.25 mg/mL, glutamic acid decarboxylase activity of 410 U/L, a 4.5-fold increased than before optimization. After strain LB-8 fermentation in green tea after, the tea polyphenols reduced from 25.31 mg/100 mL to 7.99 mg/100 mL after 90 days fermentation. And the contents of catechins rise firstly, than downward, theanine reduced from 183.28 ?g/g to the final 91.43 ?g/g; Tea pigment (TF)+TR/TB has been a downward trend, reduced to the final 0.07 from 1.13.