To obtain dl-nicotine as starting material for preparation of d-nicotine, racemization of nicotine catalyzed by various bases was examined. As bases, NaOH, MeONa, EtONa, t-BuOK, NaH, NaNH2, CH3SOCH2Na, and LiNEt2 were used. It was found that the rate of racemization increased with the basicity of the catalyst. In the case of NaOH, MeONa, and EtONa, the racemization rates were very slow, but in the presence of NaH, NaNH2, t-BuOK is CH3SOCH2Na, and LiNEt2, marked racemization was observed. Among them, t-BuOK is recommended for practical use, because it is easy to handle and does not generate any by-product. When nicotine, previously dried over CaH2, was refluxed for 10 min over 2 wt% of t-BuOK it completely racemized without any by-product. In an experiment involving a t-BuOK/BuOD system, the 2'-position of the pyrrolidine ring was deuterated. This fact suggested the following mechanism for the racemization : (cf bulletin from the Symposium ). Although, in general, the facility to form anions is in the order of -CH3>=CH2> CH, the above experiment methyl and methylene groups adjacent to the pyrrolidine ring nitrogen atom were not deuterated. Therefore, the exclusive deuterium incorporation into the methine group in the pyrrolidine ring was ascribed to the electronic effect of the pyridine ring adjacent to the methine group. In a racemization experiment with NaD, deuterium incorporation into the 2'-position of the pyrrolidine ring was also observed. Thus, in the case of NaH catalysis, another racemization mechanism which might involve the participation of hydride was suggested. A method of preparing d-nicotine from dl-nicotine is as follows : To a 2-liter cell suspension of Pseudomonas putida JTS-9, dl-nicotine (8g) was added. After 8-hr incubation at 28.degree.C, l-nicotine was completely metabolized, and pure d-nicotine was recovered in 85% yield from the culture broth by solvent extraction, followed by distillation.