improvement of dibenzothiophene desulfurization activity by removing the gene overlap in the dsz operon dibenzothiophene dbt and its derivatives can be microbially desulfurized by dsz enzymes we investigated the expressional characteristics of the dsz operon the result revealed that the ratio of mrna quantity of dsza dszb and dszc was 11331 however western blot analysis indicated that the expression level of dszb is far lower than that of dszc gene analysis revealed that the termination codon of dsza and the initiation codon of dszb overlapped whereas there was a 13bp gap between dszb and dszc in order to get a better steady expression of dszb we removed this structure by overlap polymerase chain reaction pcr and expressed the redesigned dsz operon in rhodococcus erythropolis the desulfurization activity of resting cells prepared from r erythropolis dr2 which held the redesigned dsz operon was about fivefold higher than that of r erythropolis dr1 which held the original dsz operon