Physicochemical analysis of initial adhesion and biofilm formation of Methanosarcina barkeri on polymer support material

Vi Nguyen, Esther Karunakaran, Gavin Collins, Catherine A. Biggs

The retention of selective biofilms of Methanosarcina species within anaerobic digesters could reduce start-up times and enhance the efficiency of the process in treating high-strength domestic sewage. The objective of the study was to examine the effect of the surface characteristics of six common polymer support materials on the initial adhesion of the model methanogen, Methanosarcina barkeri, and to assess the potential of these support materials as selective biofilm carriers. Results from both the initial adhesion tests and extended DLVO (xDLVO) model correlated with each other, with PVC (12% surface coverage/mm(2)), PTFE (6% surface coverage/mm(2)), and PP (6% surface coverage/mm(2)), shown to be the better performing support materials for initial adhesion, as well as subsequent biofilm formation by M. barkeri after 72h. Experimental results of these three support materials showed that the type of material strongly influenced the extent of adhesion from M. barkeri (p<0.0001), and the xDLVO model was able to explain the results in these environmental conditions. Therefore, DLVO physicochemical forces were found to be influential on the initial adhesion of M. barkeri. Scanning electron microscopy suggested that production of extracellular polymeric substances (EPS) from M. barkeri could facilitate further biofilm development. This study highlights the potential of using the xDLVO model to rapidly identify suitable materials for the selective adhesion of M. barkeri, which could be beneficial in both the start-up and long-term phases of anaerobic digestion.