Effect Of Extracellular Polymeric Substances On Electroactive Characteristics Of Geobacter Biofilms

Electroactive biofilm formed by electroactive microorganisms is a new type of biofilm that can transfer electrons to extracellular electron acceptors.Geobacter is the most typical electroactive microorganism.The extracellular polymetric substances(EPS)of Geobacter electroactive biofilm is involved in the electron exchange between the biofim and extracellular electron acceptors directly or indirectly.However,there are few studies focused on the EPS characteristics of Geobacter biofilm and its effect on the electroactivity of biofilm.Using Geobacter sulfurreducens and Geobacter soli as model species of the genus Geobacter,this study proved that ultrasonic method could efficiently extract EPS from Geobacter biofilms.Then ultrasonic method was used to extract EPS from Geobacter biofilms grown at different anode potentials(-0.4~0.5 V)to characterize the effect of EPS yield,EPS composition and electrochemical properties on the electroactivies of Geobacter biofilms.The results showed that with increase of anode potential,the current generated by Geobacter biofilms firstly increased and then decreased,with a maximum current value at a potential range of-0.1~0.2 V.Biofilms grown at-0.1~0.2 V yielded the most amounts of extracellular organic matters and proteins,and the highest contents of riboflavin and cytochrome C were detected in EPS extracted from these biofilms.The correlation analysis showed that at a potential range of-0.4~0.5 V the electroactivity of Geobacter biofilms was positively correlated with the electron transfer ability of EPS,and the electron transfer ability of EPS was positively correlated with the protein content of EPS.It can be seen that the anode potential can affect the electron transfer ability of EPS by regulating the yield and component characteristics of EPS,and then affect the electroactivity of Geobacter biofilms.The results of this study are beneficial to understanding the extracellular electron transport pathway of electroactive biofilms and can provide a reference for improving the performance of electroactive biofilms in practice.