When C. tropicalis W1 was grown on 4-CP as sole source of carbon, special attention must be paid to
the substrate, because of the greater toxicity of chlorophenol than phenol [26,27]. The definite fact are
also indicated in Figure 2, which shows that C. tropicalis W1 can not utilize 4-CP at concentration up to
150 ppm in 30 h, and the strain can not grow well in MSM medium with 4-CP as the sole carbon source.
Compare to the sole degradation of 4-CP, the strain W1 required much less time to remove the same
amount of 4-CP when the MSM medium also contained 150 ppm phenol. It took only 20 h to degrade 150
ppm 4-CP completely, and the degradation of 4-CP with a lag phase of 5 h, shown in Figure 2. Similar
kind of observation was made in case of biomass increase of the strain. When cultured in the mixture of
phenol and 4-CP, the strain W1 grown very well with the OD value up to 2.17. The Figure 2 indicated
that phenol could enhance the degradation of 4-CP significantly.