Cd(Ⅱ)胁迫/诱导下铜绿假单胞菌EPS组分变化及其吸附性能

Effect of Cd(Ⅱ) stress on the variation in extracellular polymeric substances composition and adsorption performance of Pseudomonas aeruginosa

产生胞外聚合物(EPS)是微生物减缓或消除不利影响的自我保护机制,其中的蛋白组分发挥着十分重要的作用.为了达到定向调控EPS的目的,本研究通过不同浓度Cd(Ⅱ)对铜绿假单胞菌进行胁迫/诱导培养,研究了胁迫前后EPS组分以及对Cd(Ⅱ)的吸附性能的变化.结果表明,Cd(Ⅱ)胁迫浓度为50 mg·L^(-1)时,EPS中蛋白产量最高,达到136.80 mg·g^(-1),较胁迫前增加了409.69%,且此时EPS对Cd(Ⅱ)的吸附能力最高.Langmuir等温模型可以很好地拟合EPS对重金属Cd(Ⅱ)的吸附,理论最大吸附量达到1663.34 mg·g^(-1),且吸附过程符合二级动力学规律.三维荧光光谱图(3D-EEM)测试表明,胁迫后EPS中蛋白质含量尤其类色氨酸含量增加明显,蛋白质在吸附过程中发挥了重要的作用;红外光谱(FTIR)分析表明胁迫后-SH、C=O、N-AH/C—N等官能团的相对浓度明显增加.胁迫/诱导下EPS产量和吸附性能明显增加,在重金属污染防治中显示出极大的应用前景.

The secretion of extracellular Polymeric Substances(EPS) is a crucial of self-protection mechanism of bacteria in unfavorable environments, and its protein components plays a very important role. In this study, Cd(Ⅱ) with different concentrations were applied to induce protein production in EPS of Pseudomonas aeruginosa, and the composition changes and the adsorption performance for Cd(Ⅱ) of EPS before and after Cd induction were investigated. The results showed that the highest protein yield of 136.80 mg·g^(-1) VSS in EPS was achieved with 50 mg·L^(-1) Cd(Ⅱ) induction, which showed an 409.69% increase of protein yield compared with that without Cd(Ⅱ) stress, and achieved the highest adsorption capacity for Cd(Ⅱ). Langmuir isotherm model could well describe the Cd(Ⅱ) adsorption by EPS, and its theoretical maximum adsorption capacity reached 1663.34 mg·g^(-1), which conformed to the second-order kinetics. Three-dimensional fluorescence spectroscopy(3 D-EEM) results showed that the protein content in EPS, especially tryptophan-like, increased significantly after Cd(Ⅱ) induction, and protein played an important role during Cd(Ⅱ) adsorption. Meanwhile, infrared spectroscopy(FTIR) analysis also showed that the relative concentration of functional groups such as -SH,c=o increased significantly after Cd(Ⅱ) induction. In summary, a high protein yield was achieved under Cd(Ⅱ) stress/induction, which improved the adsorption performance of EPS for Cd(Ⅱ), thereby showing great application prospect in the prevention and control of heavy metal pollution.