ISOLATION AND CHARACTERIZATION OF BETULIN TOLERANT MICROBIAL ISOLATES

Abstract

Betulin and betulinic acid are naturally occurring lupane type pentacyclic triterpenes is widely
isolated from about 25 plants around the globe. On commercial scale betulin, is specifically
collected from the bark of Betula pendula and Betula alba L. The aim of our current work was to
isolate and characterize betulin tolerant strains which are potentially active for the bioconversion of
betulin. The experiments were aimed for screening and isolating microorganisms from a natural
source in addition from culture collection centre for utilizing betulin as substrate. Three hundred
fifty isolates were screened for their tolerance to betulin in selective medium containing up to
0.003mg/ml of betulin. Isolates were tested based on their morphological, cultural characteristics,
biochemical and molecular (16S rDNA gene sequence analysis) characterization. The growth
(PCV=packed cell volume mg/ml) of betulin tolerant isolate was considered as bioconversion
efficiency of selected isolate. Three indigenous betulin tolerant bacteria (KD109, KD 136 and KD
235) which were able to use betulin were isolated, and further characterized by biochemical
methods. As a validation of betulin tolerance of isolate KD235, the fermented broth was
extracted as a product and analyzed for the presence of betulinic acid by RP-HPLC which
revealed similar results as available in previous literature. Present work represents a pioneer study
showing prokaryotic system for betulin biotransformation to give betulinic acid as a significant
compound for pharmacological applications having anti-cancer and anti-HIV activity.