The Effect of Saturated Fatty Acids on Oxygen Uptake by Penicillium Chrysogenum

Summary: The respiration of washed mycelium of Penicillium chrysogenum suspended in phosphate buffer solutions in the presence of the sodium salts of n ‐fatty acids containing even numbers of carbon atoms was examined, using mycelium which had been grown in a lactose‐corn steep liquor‐salts medium in submerged culture. At pH 6.4 and at a concentration of 1.0% (w/v), acids of short (C 2 –C 4 ) and long (C 16 –C 18 ) chain length were readily oxidized, but acids of intermediate chain length (C 8 –C 10 ) were toxic and completely inhibited even the endogenous respiration. The two latter acids were however oxidized at lower concentrations at pH 6.4. The toxicity of sodium caprate (C 10 ) also depended on the pH of the system. At pH 7.0 and above, 0.02% caprate was readily oxidized; but below pH 6.0 that concentration became increasingly toxic and at pH 4.5 all respiration was inhibited. However, even at pH 4.5 very low concentrations of sodium caprate were oxidized. At pH 6.3, 0.025% sodium caprate completely inhibited the oxidation of glucose, peptone and sodium acetate but the oxidation of oleic acid was only partially suppressed. A concentration of 0.05% was required to inhibit completely the oxidation of oleic acid.