Biosynthesis of hydrocarbons

The biosynthesis of Me3,Mel 1-29 H takes place in oenocyte cells, released into the hemolymph and transported by lipophorin to peripheral tissues (Fig. 7) [71, 231, 232]. Direct evidence for oenocytes biosynthesizing hydrocarbon has come recently with the dissociation of oenocytes from epidermal cells and in vitro incubation with labeled propionate [233]. Differential uptake of some hydrocarbons in different tissues has also been documented although the exact mechanism behind the differential placement of hydrocarbons is unknown [20,128,230,232,234]. Although the biosynthesis of hydrocarbons may not be under direct endocrine regulation supply of precursor hydrocarbon that is converted to the sex pheromone is a requirement. 

Gu, X., Quilici, D., Juarez, P, Blomquist, G. J. and Schal, C. (1995). Biosynthesis of hydrocarbons and contact sex pheromone and their transport by lipophorin in females of the German cockroach (Blattella germanica). Journal of Insect Physiology 41 257-267. 

Chu A. J. and Blomquist G. J. (1980) Biosynthesis of hydrocarbons in insects succinate is a precursor of the methyl branched alkanes. Arch. Biochem. Biophys. 201, 304-312. 

The biosynthesis of hydrocarbons occurs by the microsomal elongation of straight chain, methyl-branched and unsaturated fatty acids to produce very long-chain fatty acyl-CoAs (Figure 11.1). The very long chain fatty acids are then reduced to aldehydes and converted to hydrocarbon by loss of the carboxyl carbon. The mechanism of hydrocarbon formation has been controversial. Kolattukudy and coworkers have reported that for a plant, an algae, a vertebrate and an insect, the aliphatic aldehyde is decarbonylated to the hydrocarbon and carbon monoxide, and that this process does not require cofactors (Cheesbrough and Kolattukudy, 1984 1988 Dennis and Kolattukudy, 1991,1992 Yoder et al., 1992). In contrast, the Blomquist laboratory has presented evidence that the aldehyde is converted to hydrocarbon and carbon dioxide in a process that... 

Sterols are another class of compounds also involved in metabolic processes. They act as hormonal regulators of growth, respiration, eind reproduction in most marine oi anisms (Kanazawa and Teshima, 1971). Sterols, notably cholesterol, are also present in oi anisms as lipoproteins, probably a larger source of these compounds than as hormonal regulators. The presence of hydrocarbons in marine organisms is known, but their precise function is unclear. Farrington and Meyers (1975) review the present knowledge on biosynthesis of hydrocarbons by marine oi anisms. Alkenes appear to make up... 

Fig. 12. A head-to-head condensation mechanism proposed for the biosynthesis of hydrocarbons in plants. The expected fate of the carboxyl carbon and the methyl carbon of Ci acid participating in the synthesis of hydrocarbon is indicated.

Assuming that it works well on a commercial scale, the aforementioned process for direct biosynthesis of hydrocarbons represents the best of green chemical production. It uses a renewable feedstock that can be produced in large quantities photosynthetically. It takes place under ambient conditions of temperature and pressure with little or no input of external energy. It does not require metal catalysts and does not produce waste by-products. The diesel fuel produced is claimed to be ultraclean and does not contain potentially pollutant or toxic benzene, sulfur, and the heavy metals that can cause problems in petroleum-based fuels. 

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