Channeling of intermediates derived from medium-chain fatty acids and de novo-synthesized fatty acids to polyhydroxyalkanoic acid by 2-bromooctanoic acid in Pseudomonas fluorescens BM07

2-Bromooctanoic acid (2-BrOA) is known to block the formation of polyhydroxyalkanoic acid (PHA) in Pseudomonas fluorescens BM07 without any influence on the cell growth when grown on fructose, but it inhibits the cell growth when grown on octanoate (OA) (Lee et al., Appl. Environ. Microbiol. 67: 4963-4974, 2001). We investigated the role of 2-BrOA in the PHA synthesis of the bacterium grown with mixtures of fructose and fatty acids. OA, 11-phenoxyundecanoic acid (11-POU), and 5-phenylvaleric acid (5-PV) were selected as model substrates. When supplemented with 50 mM fructose, all these carboxylic acids suppressed the formation of PHA from fructose, however, the P-oxidation coenzyme A monomers derived from the carboxylic acids were efficiently polymerized, but the conversion yield [(mol of carboxylate substrate converted into PHA)/(mol of carboxylate substrate in the feed)] was low (e.g., maximally similar to53% for 5 mM 11-POU). Addition of 2-BrOA (up to 5 mM) to the mixed carbon sources raised the conversion yield sensitively and effectively only at low levels of the acid substrates (e.g., 2 mM 11-POU or 5 mM OA): For instance, 100% of 2 mM 11-POU were converted into PHA in the presence of 5 mM 2-BrOA, whereas only similar to10% of the 11-POU were converted in the absence of 2-BrOA. However, at highly saturated suppressing levels (e.g., 5 mM 11-POU), 2-BrOA inhibitor showed no significant additional effect on the conversion (60-70% conversion irrespective of 2-BrOA level). The existence of competitive and compensative relationship between 2-BrOA and all the carboxylic acid substrates used may indicate that all the acid substrate-derived inhibiting species bind to the same site as the 2-BrOA inhibiting species does. We, therefore, suggest that 2-BrOA can be used for efficiently increasing the yield of conversion of expensive substituted fatty acids into PHA and then substituted 3-hydroxyacids by hydrolyzing it.