Microbiological screening for aloin metabolism and preliminary study of its enzymatic properties

A E. coli (BL21 (DE3) , PET28 (a) ) (ECUST0416, CGMCC NO. 6114) was obtained by Genetic Engineering Technology as the target bacteria which produced protease converting aloin into aloe-emodin. 148U of protease in 1L fermented culture medium could be achieved under the fermentation conditions as 30℃, 250r/min for 11h. The enzymatic activity was studied and the best activity determination method was:5mL crude enzyme, 5mL 40mmol/L Phosphate Buffer (pH7. 5) , Snbstrate concentration 3mg/mL, NaCl 0. 6%, reaction at 30℃ and pH7. 5 for 20min. The enzymatic biotransformed product was determined by HPLC with a purity of 98. 5% and identified as aloe-emodin by MS and NMR.