Formation and characterization of extracellular polymeric substance from Shewanella xiamenensis BC01 under calcium stimulation

The widely distributed genus Shewanella is famous for its capacity of electron transferring and extracellular polymeric substance (EPS) production. Regarding to the EPS production by Shewanella is a critical event for its application, the aim of this study is to decipher the effect of calcium ion on a new S. xiamenensis BC01 (SXM). It grew and survived at a high concentration of 20 mM CaCl₂ in LB medium. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that calcium had an effect on cell resulted in the stimulating EPS production and changing morphology of nano-filament. Further characterization of the EPS through attenuated total reflectance of Fourier transform infrared (ATR-FTIR) spectroscopy, and protein identification of whole cell via SDS-PAGE coupled with tandem mass spectrometry implied calcium affected membrane and flagellum structure. The flagellin domain-containing protein was found to be relative with the process of flagella assembling, which enhanced EPS formation. Finally, the production of EPS increased from 0.35 g/L to 1.7 4g/L was corresponding to the increment of calcium. Thus, the decolorization rate of azo dye reactive blue by EPS was increased from 26.5 % to 49.5 % upon the addition of calcium.