Oleic acid as a substrate for poly-3-hydroxyalkanoate formation in Alcaligenes eutrophus and Pseudomonas putida

Abstract

Poly-3-hydroxyalkanoates (PHAs) are bacterial polyesters which have, due to their biodegradability, attracted considerable industrial interest. Our research aim is to extend the application potential of PHAs by improving the efficiency of the PHA production process and by increasing the range of polymers which can be produced. To this end we have investigated whether LCFAs derived from vegetable oils can be an alternative feedstock for the production of PHB. Our results showed that high cell yields with up to 65% PHB could be obtained after growth of Alcaligenes eutrophus on oleic acid as the sole source of carbon and energy. The PHB yield was almost twice the yield obtained with carbohydrates, which currently are used as feedstocks for PHB production. In addition it was shown that poly(3-hydroxybutyrate-co-3-hydroxy-valerate) is synthesized when a mixture of oleic acid and nonanoic acid is supplied as feedstock. Recently, it was discovered that pseudomonad strains can accumulate PHA consisting of medium-chain-length fatty acid during growth on aliphatic substrates. In this study we have used GC-MS and 1H NMR to analyze PHAs formed by P. putida during growth on oleic acid. The polymer was found to consist of five different monomers, which are derived from sequential 3-hydroxy fatty acid intermediates in the beta-oxidation cycle. These results indicate that a series of novel PHAs can be produced by P. putida from the available variety of LCFAs derived from vegetable oils.