Abstract:To study the effect of positive mutant on the degradation of ester catechins in green tea, the thermal stability and specific enzyme activity of Lactobacillus plantarum tannase (Lptan1) were improved through directed evolution.. A mutant library of Lptan1 was constructed by error-prone PCR, and the mutants with enhanced thermostability and specific enzyme activity were screened and expressed in Escherichia coli. The application of these mutants in hydrolyzing ester catechins in green tea was further evaluated. A positive mutant (mLptan1) was selected with an optimal temperature (45 ℃) that was 5 ℃ higher than that of Lptan1 (40 ℃). Its specific enzyme activity (425.6 U/mg) was 1.36 times higher than that of Lptan1 (312.3 U/mg). When mLptan1 was applied to degrade green tea soup, the degradation rate of ester catechins reached 85% after hydrolysis at 1 U/mL and the optimal reaction temperature for 120 min, while the degradation rate of Lptan1 was only 65%. Directed evolution significantly improved both the optimal temperature of Lptan1 and the degradation rate of ester catechins in tea soup, which has a good application prospect in tea beverages.
