Compositional shifts in lipid fractions during lipid turnover in Cunninghamella echinulata

The oleaginous fungus Cunninghamella echinulata when cultivated on a tomato waste hydrolysate medium accumulated 7.8 g l−1 of reserve lipid, while, after the exhaustion of the carbon source in the growth environment, 44% of this lipid was consumed and 3.2 g l−1 of lipid-free biomass were synthesized. It was demonstrated that lipid fractions and individual lipid classes varied in amount, relative proportions and fatty acid profile during the turnover phase. Triacylglycerols (TAG) were preferentially consumed as their percentage proportion decreased from 26.6 to 6.9% (w/w) of lipid-free biomass, while TAG structures containing more unsaturated fatty acids were partially discriminated. Consequently, the relative proportion of γ-linolenic acid (GLA) increased in TAG from 9.2% (end of the lipogenic phase) to 15.3% (w/w), whereas C16:0 decreased from 22.7 to 15.6% (w/w). Concomitantly membrane polar lipid fractions were synthesized during lipid turnover. During the transition, glycolipids plus sphingolipids fraction was enriched in polyunsaturated fatty acids, especially in GLA, while phospholipids fraction was enriched in GLA but not in C18:2.