Production of trans-2-methyl-5-isopropylhexa-2,5-dienoic acid by Pseudomonas rhodesiae CIP 107491

The feasibility of trans-2-methyl-5-isopropylhexa-2,5-dienoic acid (novalic acid) accumulation using the α-pinene degradation pathway of Pseudomonas rhodesiae CIP 107491 was studied. This appeared possible by using concentrated living bacterial cells produced under oxygen limitation with α-pinene as sole carbon source. The second step of the process, the bioconversion itself, had to be performed without oxygen limitation due to the need for cofactor regeneration. Results showed that a not yet reported cofactor-dependent enzymatic isomerization of isonovalal into novalal was likely to occur and that both aldehyde isomers could be oxidized to the corresponding acid. Precursors tested, α-pinene oxide and isonovalal had a strong permeabilization effect on bacterial cells. This effect, which increased from the oxide to the aldehyde, led to an inactivation of the respiratory chain and to acids synthesis stop. Present results allowed to obtain about 12 g/L acids (80% novalic acid) with an average yield close to 50% after 12 h reaction in a biphasic system using α-pinene oxide as precursor .