The oxidation of fatty acids by mycelium of Penicillium roqueforti.

SUMMARY Low concentrations of fatty acids with less than 14 carbon atoms were oxidized without a lag phase over a wide range of pH values by mycelium of Penicillium roqueforti. The effect of the fatty acids upon oxygen uptake by a given weight of mycelium, and the nature of the products of oxidation, were dependent upon the concentration and chain length of the fatty acid and the pH value of the system. The C,-C,, fatty acids which showed the greatest inhibitory effect were not oxidized to the corresponding methyl ketone with one less carbon atom in such high yields as the less toxic C,-C, acids. The Co-Cs fatty acids markedly inhibited endogenous respiration at low pH values but this inhibition was reversed by increasing the pH value. The toxic effect associated with some fatty acids was less pronounced against mycelium which had been previously shaken over an extended period in phosphate buffer. It is suggested that the cellular regulation of fatty acid oxidation and methyl ketone formation involves deacylation of p-0x0 acyl thiolester which provides an alternative means of recycling coenzyme A when oxidation of acetyl CoA is impaired.