Characterization of exopolymeric substances from selected Rhodopseudomonas palustris strains and their ability to adsorb sodium ions

Removal of Na+ by binding with exopolymeric substances (EPS) from Rhodopseudomonas palustris TN114 and PP803 was investigated. The moderate negative correlation pairs (r(p)) between remaining Alcian blue and amount of Na+ adsorbed on EPS from strains TN114 and PP803 were -0.652 and -0.609. Both strains showed positive relationships between the amounts of EPS produced and bacterial growth. EPS from strain PP803 had a higher efficiency in removing Na+ than the EPS from strain TN114 based on their EC50 values (1.79 and 1.49 mg/mL for TN114 and PP803, respectively). The principal component from EPS of strain PP803 which was responsible for salt removal was purified and it was identified as a polysaccharide kDa) mainly composed of galacturonic acid. Overall results suggested that EPS is a key factor that our strains used to bind Na* allowing their survival in high NaC1 concentrations. (C) 2014 Elsevier Ltd. All rights reserved.