Formation of monohydroxy- n-nonane-2-ones from tricaprin by Fusarium avenaceum f. sp. fabae IFO 7158

Abstract

Fusarium avenaceum f. sp. fabae IFO 7158 metabolized tricaprin with accumulation of n-nonane-2-one and three unknown minor compounds in the medium. The three compounds were identified to be 8-hydroxy- n-nonane-2-one, 7-hydroxy- n-nonane-2-one, and 6-hydroxy- n-nonane-2-one. The accumulation of the monohydroxy- n-nonane-2-ones took place with a decrease in n-nonane-2-one (C 9:0-2-one) once formed from capric acid (C 10:0). Thus, it is speculated that hydroxylations of n-nonane-2-one at ω2, ω3, and ω4 carbons gave the 8-hydroxy-, 7-hydroxy-, and 6-hydroxy- n-nonane-2-ones, respectively. Even though the microorganism could utilize well for growth all of the synthetic triglycerides, such as tricaproin, tricaprylin, tricaprin, trilaurin, trimyristin, and tripalmitin, the monohydroxy- n-alkane-2-one was formed exclusively from tricaprin. The maximal accumulation of monohydroxy- n-nonane-2-ones, a mixture of 8-hydroxy-, 7-hydroxy- and 6-hydroxy- n-nonane-2-ones in an approximate ratio of 10:7:0.5, was 139 mg from 1.0 g tricaprin. Finally, a novel metabolic pathway for the medium chain fatty acid in the fungus is discussed.