Chapter 44 



Degradation of 2-Methylhexane by a 

 Pseudomonas 



A. C. Van Der Linden and G. J. E. Thijsse 



I 



n recent years our knowledge of bacterial metabolism of alkanes 

 has been greatly enlarged. As late as 1956, at the Symposium 

 on Petroleum Microbiology, Kallio had to infomi the audience 

 of the "murky state of the problem" and further stated that - in 

 the absence of positive identification of intermediates - "any dis- 

 cussion of mechanisms was premature ( 1 ) ." 



At present most investigators will agree on the following 

 major principles of alkane oxidation: 



1) n- Alkanes are oxidized far more easily than branched 

 ones. 



2) The predominant alkane oxidation system attacks the 

 molecule at a terminal methyl group. 



3 ) The corresponding fatty acids are formed via the primary 

 alcohol and the aldehyde. 



4) The fatty acids are broken down by i^-oxidation, ex- 

 cluding participation of a decarboxylation reaction. 



This distinct progress in our knowledge prompted us to 

 extend our work to the branched paraffins. These hydrocarbons 

 generally contain non-equivalent methyl groups, and it would 

 be interesting to see what is the preferred oxidation route. Con- 

 sequently, an investigation into 2-meth\'lhexane oxidation has 

 been started, the central question being whether the oxidation 

 of 2-methylhexane starts at Ci or - as we must expect from the 

 high oxidation rates of n-alkanes - at Cr,. 



Applying existing knowledge in the field of methyl-substi- 

 tuted fatty acid metabohsm ( 3 ) we may postulate two degrada- 

 tion schemes, viz. a "Ci-scheme" and a "Co-scheme." 



475 



