Control of lipid accumulation in the yeast Yarrowia lipolytica.

A genomic comparison of Yarrowia lipolytica and Saccharomyces cerevisiae indicates that the metabolism of Y. lipolytica is oriented toward the glycerol pathway. To redirect carbon flux toward lipid synthesis, the GUT2 gene, which codes for the glycerol-3-phosphate dehydrogenase isomer, was deleted in Y. lipolytica in this study. This Delta gut2 mutant strain demonstrated a threefold increase in lipid accumulation compared to the wild-type strain. However, mobilization of lipid reserves occurred after the exit from the exponential phase due to beta-oxidation. Y. lipolytica contains six acyl-coenzyme A oxidases (Aox), encoded by the POX1 to POX6 genes, that catalyze the limiting step of peroxisomal beta-oxidation. Additional deletion of the POX1 to POX6 genes in the Delta gut2 strain led to a fourfold increase in lipid content. The lipid composition of all of the strains tested demonstrated high proportions of FFA. The size and number of the lipid bodies in these strains were shown to be dependent on the lipid composition and accumulation ratio.

Low concentrations of the non-ionic detergent Nonidet P-40 interfere with sterol biogenesis and viability of the yeast Saccharomyces cerevisiae.

Mild non-ionic detergents are used for solubilization of hydrophobic substrates in yeast growth media at concentrations 0.1-1%. Our data show that low concentrations of Nonidet P-40 may significantly affect lipid biogenesis in the yeast Saccharomyces cerevisiae. The uptake and esterification of external [4-14C]-cholesterol is strongly reduced in hem1 mutants treated with low concentrations of Nonidet P-40. Significant inhibitory effect of NP-40 on sterol uptake and esterification was evident both in non-growing and growing cells supplemented with external cholesterol. Increased levels of sterol precursors (squalene, lanosterol) in hem1 cells grown in complex medium with cholesterol indicated general interference of NP-40 with sterol biosynthesis. NP-40 in the growth medium affected also cell viability estimated as the colony forming ability. More attention should be therefore paid to possible effects of mild detergents at low concentrations generally considered to be harmless, especially in cells with disturbed lipid biogenesis.