Controlling the membrane fluidity of yeasts during coupled thermal and osmotic treatments

Abstract

Yeasts are often exposed to variations in osmotic pressure in their natural environments or in their substrates when used in fermentation industries. Such changes may lead to cell death or activity loss. Previous work by our team has allowed us to relate the mortality of cells exposed to a combination of thermal and osmotic treatments to leakage of cellular components through an unstable membrane when lipid phase transition occurs. In this study, yeast viability was measured after numerous osmotic and thermal treatments. In addition, the fluidity of yeast membranes was assessed according to a(w) and temperature by means of 1,6-diphenyl-1,3,5-hexatriene (DPH) anisotropy measurement. The results show that there is a negative correlation between the overall fluidity variation undergone by membranes during treatments and yeast survival. Using a diagram of membrane fluidity according to a(w) and temperature, we defined dehydration and rehydration methods that minimize fluidity fluctuations, permitting significantly increased yeast survival. Thus, such membrane fluidity diagram should be a potential tool for controlling membrane state during dehydration and rehydration and improve yeast survival. Overall fluidity measurements should now be completed by accurate structural analysis of membranes to better understand the plasma membrane changes occurring during dehydration and rehydration.

Characterization of the S. cerevisiae inp51 mutant links phosphatidylinositol 4,5-bisphosphate levels with lipid content, membrane fluidity and cold growth

“…The extent of molecular disorder and motion within a lipid bilayer is referred as fluidity of the membrane [59]. Cold and other physicochemical stressors (e.g., hydrostatic pressure and salinity) cause a decrease in membrane fluidity referred as "rigidification" which compromises its functionality and limits cell growth [1,2,43,60,91]. Such modification triggers a regulatory response in most organisms that ultimately leads to acclimation.…”

Influence of initial glucose concentration on seed culture of sodium gluconate production by Aspergillus niger

“…Similarly, the groups A, B, and E with low or high initial glucose concentrations had low glucose consumption rate and product yield, and more metabolic flux flowed to synthesize metabolites responding to environmental stresses for facilitating cell growth. In general, there was a relatively complete strategy for microorganism to respond to osmotic stress, containing the selfsynthesis or exogenous uptake of compatible solutes and osmoprotectants, metabolic flux redistribution, and membrane fluidity variations (Schubert et al 2007;Saum and Müller 2007;Simonin et al 2008;Varela et al 2003).…”

Changes in SAM 2 expression affect lactic acid tolerance and lactic acid production in Saccharomyces cerevisiae

“…Therefore, during detoxification, the protons are expelled via the H + -ATPase pump and the anions via active export systems (or metabolized), consuming huge amounts of energy. There is no surprise then in finding that membrane lipids and proteins are among the first targets of modification induced by some specific stresses [28][29][30][31][32].…”