n-Alkane Utilization and Lipid Formation

Utilization of various hydrocarbons by microbes is well known (Beerstecher, 1954), but little has been reported on the cellular composition of hydrocarbongrown cells. No doubt it has been assumed that these cells differ little from those cultivated on nonhydrocarbon substrates and, in general, this assumption is probably true. But it is recognized that substrates and cultural conditions can influence not only extracellular products but also the composition of microbial cells. In the course of studying conditions for rapid utilization of hydrocarbons by microbes we have observed a marked increase in the lipid content of nocardia grown on liquid n-alkanes. This was noted particularly in the case of n-hexadecane and n-octadecane cultures. As much as 70 per cent of the cellular material formed from these substrates can be extracted with fat solvents. This lipid consists principally of glycerides and straight-chain waxes. In contrast, nocardial cells grown on n-hexane or n-tridecane contain about the same amount of lipid as glucose-grown cells, less than 30 per cent, and no waxes. This paper describes the conditions used for cultivating a soil-isolated nocardia on liquid n-alkanes; the conversion of n-alkane to gross cellular products; and some of the factors which influence growth and cellular lipid formation.