Microbiological oxidation of long-chain aliphatic compounds. I. Alkanes and alk-1-enes.

Abstract

The yeast Torulopsis gropengiesseri converts long-chain alkanes into glycolipids which incorporate oxidised derivatives of the alkanes. Comparison of the lipid constituents of glycolipids derived from C12—C24 alkanes, a variety of oxygenated alkane derivatives, and a series of methyl β-alkoxypropionates has indicated that the major pathway of alkane metabolism involves the formation of alkan-1-ols which are subsequently dehydrogenated to the corresponding alkanoic acids. These acids are metabolised, either by β-oxidation, or by hydroxylation to give ω-hydroxy-acids (and subsequently αω-dicarboxylic acids) and, by a stereospecific hydroxylation, ω-1-hydroxy-acids. The oxidised alkanoic acids are protected from further degradation by incorporation into glycolipids. The chain-length of an alkanoic acid determines (i) whether β-oxidation or hydroxylation is the predominant reaction, and (ii) whether hydroxylation takes place mainly at the ω- or the ω-1-position. Both ω- and ω-1-hydroxylations of alkanoic acids are most efficient when the site of hydroxylation and the carboxy-group are separated by a chain of fourteen methylene groups. It is proposed that these hydroxylations may be brought about by a single enzyme. A minor pathway of alkane metabolism involves the formation of alkan-2-ols which are incorporated into glycolipids and not oxidatively metabolised. Fermentations of long-chain alk-1-enes yield glycolipids which incorporate ω-1-hydroxy-acids, ω-hydroxy-acids, and αω-dicarboxylic acids which are derived from the alk-1-enes both with and without loss of a carbon atom.