Branched alkanes degradation

The degradation of squalene by Marinobacter sp. strain 2sq31 (Rontani et al. 2002) is initiated by oxidative fission, although the subsequent steps are carried out by ()-oxidation and carboxylation that are comparable to those used for branched alkanes. 

Contaminants in recycled plastic packaging waste (HDPE, PP) were identified by MAE followed by GC-MS analysis [290]. Fragrance and flavour constituents from first usage were detected. Recycled material also contained aliphatic hydrocarbons, branched alkanes and alkenes, which are also found in virgin resins at similar concentration levels. Moreover, aromatic hydrocarbons, probably derived from additives, were found. Postconsumer PET was also analysed by Soxhlet extraction and GC-MS most of the extracted compounds (30) were thermally degraded products of additives and polymers, whereas only a few derived from the original contents... 

Susceptibility to n-alkane degradation is an inverse function of chain length. Branched alkanes are less susceptible than straight-chain n-alkanes, and the most resilient saturated components are the pristine and phytane isoprenoids (Wang et al. 1998). 

Fig. 4. 26 Possible reaction schemes involved in alkane formation from thermal degradation of kerogen (a) radical reactions in w-alkane generation (b) carbocation reactions in methyl-branched alkane generation (after Kissin 1987).

E. J. McKenna, Microbial metabolism of normal and branched alkanes, in Degradation of Synthetic Organic Molecules in the Biosphere, Natl. Acad. Sci, Washington D.C., 1972, p. 73. 

Marine bacteria and yeast may ameliorate the effects of the apparently inevitable oil spillages at sea . Hundreds of such organisms have been isolated from the Arctic that can metabolize diesel oils down to 10 °C and bacterial communities that can degrade n-chain and branched alkanes have been characterized ... 

It can be seen that major differences occur in the products of thermal degradation that are obtained for these three similar polymers. PE produces major amounts of normal to Cg alkanes and minor amounts of 2-methyl and 3-methyl compounds such as isopentane and 3-methylpentane, indicative of short-chain branching on the polymer backbone. For PP, branched alkanes predominate, these peaks occurring in regular patterns, e.g., 2-methyl, 3-ethyl, and 2,4-dimethylpentane and 2,4-dimethylheptane, which are almost absent in the PE pyrolysate. Minor components obtained from PP are normal paraffins present in decreasing amounts up to -hexane. This is to be contrasted with the pyrogram of PE, where n-alkanes predominate. The ethylene-propylene copolymer, as might be expected, produces both normal and branched alkanes. The concentrations of 2,4-dimethylpentane and 2,4-dimethylheptane are lower than those that occur in PP. 

Berekaa, M.M. SteinbUchel, A. Microbial degradation of the multiply branched alkane 2,6,10,15,19,23-hexamethyltetracosane (squalane) by Mycobacterium fortuitum and Mycobacterium ratisbonense, Appl.Environ.Microbiol., 2000, 66, 4462-4467. 

Petroleum, or crude oil, is believed to be the product of microbial degradation of living organic matter that existed several hundred million years ago. Crude oil, a dark viscous Uquid, is primarily a mixture of several hundred different hydrocarbons, particularly straight-chain alkanes, some branched alkanes, and varying quantities of aromatic hydrocarbons. Distillation yields several fractions with a typical product distribution, as shown in Table 3-3. The composition of petroleum varies widely, depending on the origin of the oil. 

Some insects use hydrocarbons as sex pheromones. For example, the housefly, Musca domestica, uses a mixture including (Z) -9-tricosene, the corresponding epoxide and ketone, and several methyl alkanes (2iI). The tricosene is derived by chain elongation of oleic acid, and the epoxide and ketone are made from it. The methyl alkanes are made de novo from acetate and propionate, with one propionate unit per molecule supplying the branch carbon. Propionate can arise from the degradation of valine or isoleucine, but not from succinate, although succinate may serve as an acetate precursor. 

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