A study on cell surface hydrophobicity, growth and metabolism of Zymomonas mobilis influenced by PEG as a pretreatment agent

Abstract

This study investigates the effects of polyethylene glycol (PEG) 4000, a non-ionic surfactant, on the cell surface hydrophobicity (CSH) of Zymomonas mobilis, as well as its growth and metabolism. Different concentrations of PEG were used in the fermentation medium to determine the toxic concentration of PEG on Z. mobilis. PEG in 1% (w/v) did not influence growth, but increased glucose consumption and bioethanol production yield by 20 and 30%, respectively. PEG in 3% diminished the growth profile slightly and had a negligible effect on glucose consumption, while the bioethanol production yield was increased. However, 5% PEG inhibited growth considerably and glucose consumption was decreased. An increased concentration of PEG caused increased CSH values of cells cultivated for 12 h under anaerobic conditions. The results indicate the hormetic effect of PEG, which stimulates bioethanol production at low concentrations and impedes growth and metabolism in a 5% concentration by altering the hydrophobicity of the cell surface.