Isolation, identification and degradation characteristics of Enterobacter sp. B-20 from malachite green degradation bacteria

A strain with powerful ability of malachite green degradation was screened from the malachite green polluted sediments in freshwater fish culture ponds. The strain was identified as Enterobacter sp. B-20 by 16S rRNA gene sequence and phylogenetic tree analysis. We applied KBH₄ reduction-HPLC method to study the malachite green degradation characteristics of Enterobacter sp. B-20. It is showed that malachite green had an inhibitory effect on the growth of Enterobacter sp. B-20. This strain could degrade over 97% malachite green at 5–12 mg·L^-1 within 12 h, and the malachite green degradation rate was over 82% at 1–40 mg·L^–1 malachite green within 24 h. The malachite green degradation rate significantly increased with increase of pH, and the maximum malachite green degradation rate was found at pH 9. Enterobacter sp. B-20 exhibited high salt tolerance and had stable malachite green degradation at 10–40 g·L^–1 NaCl concentration. Enterobacter sp. B-20 showed strong metal ion tolerance and stable malachite green degradation at high concentrations of metal ions. The metal ions including Fe³⁺at 0.1–1 mmol·L^–1, Cu²⁺ at 0.1–0.5 mmol·L^–1, Mn²⁺ at 0.1 mmol·L^–1 and Pb²⁺ at 0.1–1 mmol·L^–1 increased the malachite green degradation rate of Enterobacter sp. B-20 significantly. The results indicate that it is potential to use Enterobacter sp. B-20 for malachite green degradation in complex aquaculture environment.