Objective: To optimize bioconversion process of baicalin to baicalein in Scutellariae Radix by bacillus natto. Method: HPLC was employed to determine the content of baicalein with mobile phase of methanol (A)-acetonitrile (B)-0.2% phosphoric acid water solution (C) for gradient elution (0-28 min

20%-35%A

20%-35%B;28-32 min

35%-20%A

35%-20%B) and detection wavelength at 278 nm.Based on single factor tests

orthogonal test was adopted to optimize fermentation process by taking bacteria age

grinding degree

solid-liquid ratio and inoculation amount as factors. Result: Optimum fermentation process was as following:bacteria age of 12 h

solid-liquid ratio of 1:3

grinding degree of 40 mesh

inoculation amount of 30%

fermentation temperature of 37 ℃ and fermentation time of 7 d.Mass fraction of baicalein was 10.02% and conversion rate of baicalin was 96.5%. Conclusion: This optimized fermentation process is feasible and stable

baicalin in Scutellariae Radix basic transforms into baicalein by bacillus natto

it can upgrade medicinal value and physiological activity of Scutellariae Radix.