Xanthan Production by Mutant Strain of Xanthomonas campestris TISTR 840 in Raw Cassava Starch Medium

Raw cassava starch was used as carbon source in growing Xanthomonas campestris TISTR 840 for xanthan production due to its cheap price and mass production in Thailand. However, xanthan production with raw cassava starch yielded low content (4.31 g/l). A low level of amylase was detected in the XOL medium of X. campestris when raw cassava starch was used. Treatment of X. campestris TISTR 840 with ethyl methansulfonate resulted in the isolation of Xc-M, a strain that showed highest amylase overproduction. When cultured in bioreactor with a medium containing raw cassava starch, the growth of Xc-M cells was significantly higher than that of the wild type. The mutant produced 3.46- and 1.39-fold increased amylase activity and xanthan yield, respectively. Xc-M is useful for xanthan production in media containing raw starch as a carbon source.