THE INFLUENCE OF MEMBRANE COMPOSTION ON ACETIC ACID PERMEABILITY AND POTENTIALLY ACETIC ACID TOLERANCE

Other, 2014

Compounds entering the cell do so either by passive diffusion over the plasma membrane or through transporters in the membrane. The specific lipid composition of the plasma membrane influences both the passive diffusion rate but also the activity of membrane proteins. Acetic acid, a major hurdle in fermentation processes using lignocellulosic material, is believed to pass through the membrane in its protonated from mainly by passive diffusion [1]. Sterols and sphingolipids are lipid classes thought to contribute to membrane rigidity. Sterols are often found to be involved in stress resistance [2, 3] and in our previous work sphingolipids were pointed at as an important constituent of the plasma membrane of the yeast Zygosaccharomyces bailii, known to be very tolerant to acetic acid, suggesting a possible link between acetic acid tolerance and sphingolipid relative abundance in the membrane [4]. Here we will provide supporting evidence of the importance of sphingolipids and sterols in acetic acid membrane permeability. We have combined biochemistry techniques with in silico membrane modeling to answer the question how membrane engineering can be used to decrease acetic acid membrane permeability. [1] Verduyn et al. Yeast (1992) 501-517. [2] Alexandre et al. FEMS Microbiology Letters (1994) 124:17-22. [3] Liu et al. Journal of Applied Microbiology (2013) 114:482-491. [4] Lindberg et al. PlosONE (2003) 8(9): e73936.