Effect of Citric Acid on Cell Membrane Structure and Function of Issatchenkia terricola WJL-G4.

AIMS: This study aimed to investigate the changes of cell membrane structure and function of Issatchenkia terricola under citric acid by performing physiological analysis.

METHODS AND RESULTS: The membrane integrity, surface hydrophobicity, structure, fluidity, apoptosis and fatty acid methyl esters composition of I. terricola WJL-G4 cells were determined by propidium iodide staining, microbial adhesion to hydrocarbon test, transmission electron microscopy analysis, fluorescence anisotropy, flow cytometry and gas chromatography-mass, respectively. The results showed that with the increasing of citric acid concentrations, the cell vitality, membrane integrity and fluidity of I. terricola reduced; meanwhile, apoptosis rate, membrane permeable, hydrophobicity and ergosterol contents augmented significantly. Compared to control, the activities of Na+,K+-ATPase and Ca2+,Mg2+-ATPase increased by 3.73-fold and 6.70-fold, respectively, when citric acid concentration increased to 20 g L-1. The cells cracked and their cytoplasm effused when citric acid concentration reached 80 g L-1.

CONCLUSIONS: I. terricola could successfully adjust its membrane structure and function below 60 g L-1 of citric acid. However, for citric acid concentrations above 80 g L-1, its structure and function were dramatically changed, which might result in reduced functionality.