In order to biotransform phillyrin into phillygenin,the strains which could biotransform phillyrin into phillygenin were screened and identified from human intestinal flora by spreading plate method and 16S rDNA sequencing with the yield of phillygenin as the evaluation index.In order to improve the stability and efficiency of the strain,immobilized microorganism technology was used to optimize the preparation conditions for immobilization of bacterial balls and the reaction conditions for biotransformation of phillyrin into phillygenin.The results indicated that a novel Escherichia coli strain was isolated from human intestinal bacteria.The strain could efficiently biotransform phillyrin into phillygenin without the by-products.The optimized preparation conditions for immobilization of bacterial balls were as follows sodium alginate of 3%,calcium chloride of 3.5%,and crosslinking time of 3 h.Under substrate concentration of 0.8 mg/mL in pH 8.0 at 39 °C,the phillyrin was completely biotransformed into phillygenin in about 25 h,and the yield of phillygenin was 97.0%.Moreover,the transformation rate of phillyrin could still reach 70.2% after the immobilized balls were recycled for 13 times.