Culture at 27 ℃ for 24-28h, and then inoculate the seed culture solution to the sterilized benzene contained in the fermentation tankSterile air was introduced into the precursor of acetic acid, stirred and grown at 27 ℃ for 7 days. In the process of fermentation, it is necessary to add phenylacetic acid precursor and appropriate medium. ② Extraction and purification: cool and filter penicillin fermentation liquid.