Membrane engineering for reduced acetic acid stress: insights from Zygosaccharomyces bailii

The high concentration of acetic acid released during pretreatment of lignocellulose raw material is a major obstacle to the microbial production of bio-based products. Acetic acid enters the cell mainly by passive diffusion across the plasma membrane and inhibits yeast by mechanisms such as reduction of intracellular pH, accumulation of the acetate anion, and by signaling effects triggering cell death.

Through extensive characterization of the acetic acid tolerant yeast Zygosaccharomyces bailii, we have identified the cell membrane as a target for strain engineering with potential to increase acetic acid tolerance in Saccharomyces cerevisiae.

We propose membrane permeability as a key component for Z. bailii’s acetic acid tolerance. We have previously shown that Z. bailii has a unique ability to remodel its plasma membrane upon acetic acid stress, to strongly increase its fraction of complex sphingolipids, at the expense of a drastic reduction of glycerophospholipids [1].

Here we further demonstrate the involvement of complex sphingolipids in acetic acid tolerance by decreasing sphingolipid synthesis using the drug myriocin, and characterize the acetic acid tolerance in terms of growth, intracellular pH and intracellular acetate accumulation. Furthermore we show the impact of complex sphingolipids on membrane physical properties using in silico membrane simulations. Ongoing membrane engineering of S. cerevisiae can potentially give additional strength to our findings.

[1] Lindberg et al. PlosONE (2003) 8(9): e73936.