藻菌生物膜胞外聚合物(EPS)与Al^3＋的配位作用机理

Characterization of the Complexation Between Al^(3+) and Extracellular Polymeric Substances Prepared from Alga-bacteria Biofilm

利用三维荧光光谱(3DEEM)和傅立叶转换红外光谱(FTIR)研究了藻菌生物膜EPS与Al3+的相互作用机理.3DEEM结果表明,生物膜EPS含有3个荧光峰.其中,峰A(Ex/Em=225～235nm/300～330nm)和峰B(Ex/Em=275～280nm/325～330nm)荧光较强,属类蛋白峰,峰C(Ex/Em=335nm/432～434nm)荧光较弱,属类腐殖酸峰.峰A和峰B都能不同程度地被Al3+猝灭,它们的条件稳定常数(logK)分别为5.89和6.95.Al3+-EPS体系的峰A和峰B荧光强度明显受溶液pH值的影响.在pH为2～4之间时,荧光强度随pH的增大而增大,在4～7之间随pH的增大而减小,在7～11之间随pH增大而增大.FTIR光谱图分析表明,Al3+主要与EPS中所含的—NH—、C==O等发生强的配位作用.

Three-dimensional excitation emission matrix fluorescence spectroscopy （3DEEM） and fourier transform infrared （FTIR） spectroscopy were used to study the extracellular polymeric substances （EPS） produced by alga-bacteria biofilm. Three excitation/emission （Ex/Em） fluorescence peaks at Ex/Em 225-235/300-330 nm （Peak A）, 275-280/325-330 nm （Peak B）, and 335/432-434 nm （Peak C） were identified in the 3DEEM, respectively. Peaks A and B were referred to as proteinlike fluorescence and peak C as humic-like fluorescence. The fluorescence intensity at both peaks A and B decreased as Al^3＋ concentration increased. The values of logK （conditional stability constant） for peaks A and B were 5.89 and 6.95, respectively. It was a/so found that solution pH strongly affected the fluorescence intensity at peaks A and B for the Al^3＋-EPS complexation. The fluorescence intensity at peaks A and B increased consistently with solution pH increasing from 2 to 4, decreased with solution pH increasing from 4 to 7, and increased again with solution pH increasing from 7 to 11. FTIR analysis demonstrated that --NH-- and C==O groups in EPS were responsible for binding with Al^3＋.