The fungal production of polyunsaturated fatty acids currently considered to be of dietetic importance

Kendrick, Andrew John

Abstract

Seventeen fungi were grown in submerged culture and their lipids extracted. Accumulation of over 20% (w/w) lipid in the biomass was correlated with the presence of ATP:citrate lyase. Phospholipids contained the greatest proportion of polyunsaturated fatty acids (PUFAs). However, unlike other fungi, Thraustochytrium aureum (ATCC 34304) produced the triacy1g1ycero1 fraction as the most unsaturated. Experiments failed to produce cultures of T.aureum with a lipid content greater than 15% (w/w). This correlated to the lack of ATP:citrate lyase activity.

Lipid extracted from oleaginous fungi grown on oils as sole carbon source had fatty acid profiles similar to that of the carbon source. Malic enzyme was repressed in oi1- grown cultures therefore fungi lost lipogenetic capacity (due to NADPH limitation) and utilised presented fatty acids.

Sesamol (methy1enedioxyphenol), supplementation of Mucor circinclloides cultures, caused a switch from lipid accumulation to alcohol production. Malic enzyme activity in such cultures was <2% of the control value and thus its absence lead to a severe deficiency of NADPH and curtailment of fatty acid biosynthesis.

Entomorphthora exitalis was grown in continuous culture, over a range of temperatures. As the temperature decreased lipid unsaturation increased, as did the proportion of phospholipids. Changes in lipid unsaturation could be correlated to dissolved oxygen tension. Growth of E.exitalis over a range of oxygen concentrations failed to reproduce the temperature related effects.

Stereospecific fatty acid analysis of fungal phospholipids led to the hypothesis that PUFAs derived from alpha-linolenic acid (n-3 PUFAs) are synthesised at position sn-1 of phospholipids and those derived from gamma-linolenic acid (n-6 PUFAs) are synthesised at position sn-2.

Aerobic incubation of microsomal membranes of Muc.circinelloides stimulated the elongation and desaturation of fatty acyl groups of endogeneous phospholipids (position sn-2) for 1.5 hours. Malate stimulated the reactions to proceed for up to 4 hours via NADPH generation by microsomal malic enzyme.

Citation

Kendrick, A. J. The fungal production of polyunsaturated fatty acids currently considered to be of dietetic importance. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4216010

• Thesis Type: Thesis
• Deposit Date: Oct 30, 2014
• Publicly Available Date: Feb 23, 2023
• Keywords: Applied biology
• Public URL: https://hull-repository.worktribe.com/output/4216010
• Additional Information: Department of Applied Biology, The University of Hull
• Award Date: Jul 1, 1991