The presence of different pollutants in wastewater hinder microbial growth, compromise enzymatic activity or compete for electrons required for bioremediation pathway. Therefore, there is a need to use a single microorganism that is capable of tolerating different toxic compounds and can perform simultaneous bioremediation. In the present study, nitrate reducing bacteria capable of decolorizing azo dye was identified as Bacillus subtillis sp. DN using protein profiling, morphological and biochemical tests X-ray diffraction pattern, Raman spectroscopy and cyclic voltammetry confirm that the bacterium under study possesses membrane-bound nitrate reductase and that is capable of direct electron transfer. The addition of nitrate concentrations (0–50 mM) resulted in increased biofilm formation with variable exopolysaccharides, protein, and eDNA. Fourier Transform Infrared spectrum revealed the presence of a biopolymer at high nitrate concentrations. Effective capacitance and conductivity of the cells grown in different nitrate concentrations suggest changes in the relative position of polar groups, their relative orientation and permeability of cell membrane as detected by dielectric spectroscopy. The increase in biofilm shifted the removal of the azo dye from biodegradation to bioadsorption. Our results indicate that nitrate modulates biofilm components. Bacillus sp. DN granular biofilm can be used for simultaneous nitrate and azo dye removal from wastewater.

Graphic abstract

中文翻译：

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芽孢杆菌的硝酸盐调节。生物膜成分：可持续生物修复的拟议模型

废水中不同污染物的存在会阻碍微生物的生长，损害酶活性或竞争生物修复途径所需的电子。因此，需要使用能够耐受不同有毒化合物并能够同时进行生物修复的单一微生物。在本研究中，能够使偶氮染料脱色的硝酸盐还原菌被鉴定为枯草芽孢杆菌。sp。DN 使用蛋白质分析、形态学和生化测试 X 射线衍射图、拉曼光谱和循环伏安法证实，所研究的细菌具有膜结合硝酸盐还原酶并且能够直接电子转移。添加硝酸盐浓度 (0–50 mM) 导致生物膜形成增加，具有可变的胞外多糖、蛋白质和 eDNA。傅里叶变换红外光谱显示在高硝酸盐浓度下存在生物聚合物。在不同硝酸盐浓度下生长的细胞的有效电容和电导率表明极性基团的相对位置、它们的相对方向和通过介电光谱检测的细胞膜的渗透性发生了变化。生物膜的增加将偶氮染料的去除从生物降解转变为生物吸附。我们的结果表明硝酸盐调节生物膜成分。芽孢杆菌 DN 颗粒生物膜可用于同时去除废水中的硝酸盐和偶氮染料。

图形摘要