An efficient process for the transformation of betulin to betulinic acid by a strain of Bacillus megaterium

摘要

Betulinic acid as a derivative of betulin is widely reported for its anti-HIV and antitumor activities. Betulin has three most significant positions, i.e., primary hydroxyl group at position C-28, secondary hydroxyl group at position C-3, and alkene moiety at position C-20, where chemical modifications were performed to yield pharmacologically more active derivatives. Bioconversion optimization was performed for the enhancement in the percentage of conversion using statistical approach by opting temperature, pH and betulin concentration as independent variables. Three hundred fifty isolates were screened from natural sources under selective medium containing up to 3 g/l of betulin for their tolerance and bioconversion efficiency. Isolate KD235 was found to grow in 3 g/l betulin with 23.34 ± 0.57 g/l biomass and 0.67 ± 0.06 g/l betulinic acid production. New isolate KD235 was characterized by molecular analysis and named as Bacillus megaterium KD235. Molecular characterization of a potentially active isolate for the transformation of betulin to betulinic acid was suggested as isolate Bacillus megaterium KD235. Maximum bioconversion (22 ± 1.5%) was found at optimized conditions, i.e., pH 6.5, temperature 30 °C and at 3 g/l betulin. Validations of experiments as ~11% more bioconversion i.e., 1 ± 0.1 g/l betulinic acid were obtained using 5 l lab fermenter as compared to shake flask.