Respective effects of sodium and chloride ion on physiological property of Zymomonas mobilis 232B

Respective effects of sodium and chloride ion on growth, cell morphological changes, membrane disorganization, ion homeostasis, exoenzyme activities and fermentation performance in Zymomonas mobilis232B cultures were presented. In batch cultures containing 0.15 M NaCl, Z. mobilis232B developed filaments, and growth and ethanol production were inhibited remarkably. Chloride ion (as NH4Cl) produced similar filaments, while sodium ion (as Na2SO4) had little effect on morphology changes, indicating that filament formation in NaCl-inhibited Z. mobilis cultures is attributable to chloride ion. Furthermore, growth and ethanol production were more strongly inhibited by chloride ion than sodium ion and the damage of cell membrane under NaCl treatment was mainly caused by chloride ion. NH4+ and SO42- (as (NH4)2SO4) had little inhibitory effects at similar concentration. It was strongly suggested that the inhibitory effects of growth, fermentation performance and morphology changes of Z. mobilis232B produced by NaCl were mainly due to the chloride ion. Key words: Sodium ion, chloride ion, morphological changes, Zymomonas mobilis, fermentation.