响应面法优化黑曲霉固定化条件及其对土壤中溴氰菊酯的降解特性研究

Optimization of immobilization conditions of Aspergillus niger for degrading deltamethrin in soil

【目的】通过研究吸附包埋法固定黑曲霉(Aspergillus niger)的最佳制备工艺,初步探讨固定化黑曲霉对溴氰菊酯(deltamethrin,DM)及其中间产物3-苯氧基苯甲酸(3-phenoxybenzoic acid,3-PBA)的降解机制,并将其应用于农业种植中以评价固定化黑曲霉的实际应用效果。【方法】以生物炭、海藻酸钠为固定化载体,通过单因素和响应面试验对固定化黑曲霉(immobilized Aspergillus niger)的制备工艺进行优化。同时,利用高效液相色谱法分析DM和3-PBA的含量变化。【结果】海藻酸钠浓度、生物炭浓度和菌液接种量为DM去除率的显著影响因子,当三者分别为25.27、1.28和125.28 g/L时,是黑曲霉固定化的最佳制备条件;在施加固定化黑曲霉后,土壤中DM半衰期由7.6 d缩短至5.2 d,黑曲霉对3-PBA也具有降解作用,在21 h达到最低浓度1.45 mg/kg;修复后的土壤可显著提高番茄种子发芽率,株高、根长等6个生长指标较DM单独处理组也有不同程度的恢复;在经固定化黑曲霉修复28 d后,污染土壤根系酶活和微生物数量均得到不同程度改善。【结论】通过对黑曲霉固定化方案的优化,可显著提高其对土壤中DM的去除率;固定化黑曲霉能加快DM降解速度,对3-PBA具有同步降解作用,且其能增强污染土壤中番茄对DM的耐受性。

[Objective]To optimize the embedding-based immobilization conditions of Aspergillus niger,preliminarily study the degradation mechanism of deltamethrin(DM)and its intermediate product 3-phenoxybenzoic acid(3-PBA)by immobilized A.niger,and further evaluate the performance of immobilized A.niger applied to agricultural cultivation.[Methods]With biochar-doped sodium alginate as an immobilized carrier,we employed single factor test and response surface methodology to optimize the immobilization conditions of A.niger.The content of DM and 3-PBA was determined by high performance liquid chromatography.[Results]Sodium alginate concentration,biochar concentration,and inoculum size were significant factors affecting DM removal rate,with the optimal values of 25.27,1.28,and 125.28 g/L,respectively,for A.niger immobilization.After the application of immobilized A.niger,the half-life of DM in soil was shortened from 7.6 d to 5.2 d.Moreover,A.niger had a degradation effect on 3-PBA,which reached the lowest concentration of 1.45 mg/kg at the time point of 21 h.Impressively,the restoration with A.niger immobilization significantly improved the germination rate of tomato seeds,and recovered 6 growth indicators such as plant height and root length to varying degrees compared with the DM alone group.After 28 days of remediation by immobilized A.niger,both root enzyme activity and microbial number in the contaminated soil were improved to different degrees.[Conclusion]After optimization of the immobilization scheme of A.niger,the removal rate of DM in soil was significantly improved.The immobilization of A.niger can not only accelerate the degradation of DM and simultaneously degrade 3-PBA,but also enhance the tolerance of tomato to DM in the contaminated soil.