一株PCBs降解菌的降解特性及发酵条件优化

Degradation characteristics and fermentation conditions optimization of a PCBs-degrading strain

摘要:

【目的】针对一株多氯联苯的高效降解菌，考察其对多氯联苯(PCBs)的降解特性，并对降解条件进行优化。【方法】以不同浓度的2,4,4′-TCB与3,3′,4,4′-TCB为唯一碳源，研究苜蓿中华根瘤菌(Sinorhizobium melilon)对不同多氯联苯的降解转化能力，并进行发酵条件优化以及共代谢试验。【结果】接入菌株转化7 d后，随着底物浓度的增加，该菌对2,4,4′-TCB的降解能力呈下降趋势。在最低浓度1.0 mg/L时降解率最高，为93.3%；而在最高浓度50.0 mg/L时为65.1%。对于较难降解的四氯联苯3,3′,4,4′-TCB，菌株在最低浓度1.0 mg/L时降解率为56.2%，最高浓度25.0 mg/L时为22.8%。在温度30 °C、pH 7.0、接种量4.5 mL、装液量25 mL时，获得菌株转化10.0 mg/L 2,4,4′-TCB的最优发酵条件，7 d的降解率由原来的54.8%提高到83.6%。柠檬烯、香芹酮及甘露醇作为共代谢底物也可较好地提高菌株降解效果。【结论】苜蓿中华根瘤菌对PCBs有很好的降解效果，研究结果对PCBs的微生物降解及环境中PCBs的生物修复具有较好的意义和应用价值。

Abstract:

[Objective] This study was aimed to investigate the degradation characteristics and fermentation optimization of a PCBs-degrading strain. [Methods] The capability of Sinorhizobium melilon on PCBs degradation was studied with different concentrations of 2,4,4′-TCB and 3,3′,4,4′-TCB as the sole carbon source separately. The optimum PCBs-degrading conditions were researched by orthogonal experiment and co-metabolism experiment. [Results] The degradation rate of Sinorhizobium melilon to 2,4,4′-TCB was decreased gradually with the concentration increase of 2,4,4′-TCB. The degradation rates for 2,4,4′-TCB were 93.3% of 1.0 mg/L and 65.1% with the highest concentration up to 50.0 mg/L for 7 days, respectively. The degradation rates were 56.2% of 1.0 mg/L and 22.8% with the highest concentration of 25.0 mg/L for 3,3′,4,4′-TCB, individually. The orthogonal experiment showed that the optimal conditions for degradation process were as follows: pH 7.0, temperature 30 °C, inoculation volume 4.5 mL, medium cubage 25 mL/250 mL. Under these conditions, the degradation rate of the strain was increased from 54.8% to 83.6%. In addition, the degradation rate of PCBs was increased with limonene, corvone and mannitol as co-metabolism substratesby Sinorhizobium melilon. [Conclusion] Sinorhizobium melilon is effective in degrading PCBs and our results have significant application on the study of microbial degradation and environment bioremediation of PCBs.