Novel PHAs from unusual carbon sources: the case of Pseudomonas aeruginosa and odd-carbon fatty acids

Our research group has been involved in a systematic study on the synthesis and characterization of PHAs produced by P. aeruginosa from various fatty acids. We previously reported1 the study on the ability of P. aeruginosa to grow and synthesize PHAs from even-carbon fatty acids (EFA) from octanoic to eicosanoic and those from odd-carbon fatty acids(OFA) from nonanoic to pentadecanoic. The aim of the present study was to extend the investigations on the capability of P. aeruginosa to grow and synthesize PHAs from longer OFA upto eneicosanoic by changing microelements limiting conditions in the fermentation step. GC analysis of the 3-ydroxyalkanoate methyl esters prepared by methanolysis of PHAs obtained from OFA carbon sources allowed to establish that PHA from nonanoic acid consisted of three diff erent repeating units, that from undecanoic acid of four, that from tridecanoic of five and those from pentadecanoic, heptadecanoic, nonadecanoic, and eneicosanoic of six. In the last fi ve PHAs small amount (< 5 %) of even-carbon repeating units were detected. PHAs obtained were also characterized by 1H and 13C-NMR, GPC and DSC. The variation in the physical properties of the obtained PHAs were explored systematically in comparison to those obtained from even-carbon sources. Finally ESI MS of partially pyrolyzed samples allowed the identifi cation of oligomers up to heptamers and statistical analysis showed that these PHAs are random copolyesters.