LIPIDS OF SARCINA LUTEA. II. HYDROCARBON CONTENT OF THE LIPID EXTRACTS

Biobased production of alkanes and alkenes through metabolic engineering of microorganisms

Advancement in metabolic engineering of microorganisms has enabled bio-based production of a range of chemicals, and such engineered microorganism can be used for sustainable production leading to reduced carbon dioxide emission there. One area that has attained much interest is microbial hydrocarbon biosynthesis, and in particular, alkanes and alkenes are important high-value chemicals as they can be utilized for a broad range of industrial purposes as well as ‘drop-in’ biofuels. Some microorganisms have the ability to biosynthesize alkanes and alkenes naturally, but their production level is extremely low. Therefore, there have been various attempts to recruit other microbial cell factories for production of alkanes and alkenes by applying metabolic engineering strategies. Here we review different pathways and involved enzymes for alkane and alkene production and discuss bottlenecks and possible solutions to accomplish industrial level production of these chemicals by microbial fermentation.

C29 olefinic hydrocarbons biosynthesized by Arthrobacter species

Arthrobacter aurescens TC1, Arthrobacter chlorophenolicus A6, Arthrobacter crystallopoietes, and Arthrobacter oxydans produce long-chain monoalkenes, predominantly cis-3,25-dimethyl-13-heptacosene. Four other Arthrobacter strains did not form alkenes. The level of cis-3,25-dimethyl-13-heptacosene in Arthrobacter chlorophenolicus A6 remained proportional to cell mass during growth. cis-3,25-Dimethyl-13-heptacosene did not support growth of A. chlorophenolicus A6.

Distribution of hydrocarbons in bovine tissues

Liver, heart, kidneys, muscle and adipose (perirenal and subcutaneous) tissues were collected from six animals for analysis of their hydrocarbon composition. Qualitative and quantitative determinations were carried out by gas chromatography and combined gas chromatography-mass spectrometry. Although differing in the proportions, a homologous series of n-alkanes ranging from n-C12 to n-C31 was found in all the samples examined. The isoprenoid hydrocarbons phytane and phytene (phy-1-ene and phyt-2-ene) were also identified.

Confirmation of the identification of the major C-29 hydrocarbons of Sarcina lutea

Although there is agreement on the fact that Sarcina lutea strain FD-533 has branched C-29 monoalkenes as major hydrocarbon components, there is disagreement in the literature as to the nature of the branching. This has been resolved by analyses of the fatty acids produced by permanganate-periodate treatment of each of the resolvable hydrocarbon fractions making up the C-29 complex. The three major components are identified as doubly branched, Delta(13) species with two iso terminations, one iso and one anteiso termination, and two anteiso terminations.

Identification of fatty acids and aliphatic hydrocarbons in Sarcina lutea by gas chromatography and combined gas chromatography-mass spectrometry

The composition and nature of the fatty acids and hydrocarbons of Sarcina lutea were elucidated by gas chromatography and by combined gas chromatography-mass spectrometry. The distribution of fatty acids found in S. lutea showed two families of pairs, or dyads, of saturated monocarboxylic acids (C12-C18) with and without methyl branching. These pairs of fatty acids showed a pattern of iso and anteiso structures for C13, C15, and C17, and iso and normal structures for C12, C14, and C16. Only the C18 showed unsaturation. The distribution of hydrocarbons in the range C22-C29 showed two families of tetrads of unsaturated aliphatic hydrocarbons all showing methyl branching. Each tetrad was composed of four isomers identified as two iso olefins and two anteiso olefins. The only difference between the tetrads pertaining to different families was found in the relative gas chromatographic retention times of the last two components of each group.

14-C incorporation into the fatty acids and aliphatic hydrocarbons of Sarcina lutea

An initial investigation into the mechanism of hydrocarbon biosynthesis in Sarcina lutea was performed by measuring the amounts of (14)C incorporated into the hydrocarbons and fatty acids by use of a combination gas chromatograph and high-temperature gas-flow ionization apparatus. Uniformly labeled l-isoleucine-(14)C was predominantly incorporated into the anteiso-branched chains. Palmitate-16-(14)C gave evidence that a direct correlation may exist between the nonpolar end of the palmitate and the biosynthesis of hydrocarbons and carotenoids. The label from palmitate-1-(14)C was incorporated into the various hydrocarbon groups as a compound, derived from the polar end of the palmitate, consisting of more than two carbon atoms. Palmitate-16-(14)C and -1-(14)C gave no detectable evidence that transformed products were incorporated into other fatty acids. Sodium acetate-2-(14)C and uniformly labeled l-leucine-(14)C gave evidence of a nonspecific incorporation into both the aliphatic hydrocarbons and fatty acids of Sarcina lutea.

Aliphatic hydrocarbons and fatty acids of some marine and freshwater microorganisms

Gas chromatography and combined gas chromatography-mass spectrometry have been used to study the fatty acids and hydrocarbons of a bacterium from the Pacific Ocean, Vibrio marinus, a freshwater blue-green alga, Anacystis nidulans, and algal mat communities from the Gulf of Mexico. Both types of microorganisms (bacteria and algae) showed relatively simple hydrocarbon and fatty acid patterns, the hydrocarbons predominating in the region of C-17 and the fatty acids in the range of C-14 to C-18. The patterns of V. marinus were more comparable to those of the algal populations than to patterns reported for other bacteria. An incomplete correlation between fatty acids and hydrocarbons in both types of organisms was observed, making it difficult to accept the concept that the biosynthesis of hydrocarbons follows a simple fatty acid decarboxylation process.

THE EFFECT OF CULTURE CONDITIONS ON THE HYDROCARBON CONTENT OF CHLORELLA VULGARIS(1) (2)

Cultures of Chlorella vulgaris were grown aulo-trophically under fluorescent light and heterotrophically on glucose and inorganic salts. Hydrocarbons were extracted and analyzed by gas-liquid chromatography, molecular sieve separations, and silicic acid-AgNO3 chromatography. Chlorella vulgaris grown under both culture conditions contained a series of saturated n-paraffins ranging from 17 to 36 carbon atoms in length. This is in contrast to reports in the early literature which indicated that the hydrocarbon fraction of algae was composed of only 1 or 2 specific hydrocarbons. Only under heterotrophic conditions, however, did C. vulgaris produce 1-penta-cosene and 1-heptacosene as the primary components of the hydrocarbon mixture. Other Chlorella species were examined, but only C. vulgaris produced significant quantities of these compounds.