Exploration of α-pinene degradation pathway of Pseudomonas rhodesiae CIP 107491. Application to novalic acid production in a bioreactor

α-Pinene degradation pathway of Pseudomonas rhodesiae CIP 107491, which includes flavoring molecules like cis-2-methyl-5-isopropylhexa-2,5-dienal (isonovalal) and trans-2-methyl-5-isopropylhexa-2,5-dienoic acid (novalic acid) has been extensively studied. Studies took into account biotic and abiotic degradation phenomena, which involved isonovalal and its trans isomer, novalal. Data showed that gas stripping of aldehydes, a spontaneous autooxidation of isonovalal into isonovalic acid (cis form of novalic acid) and a cofactor-dependent isomerization of isonovalal into novalal occurred. Novalic acid was not an end product and was transformed into 3,4-dimethylpentanoic acid by fresh (non permeabilized) cells with a production yield of 40%, while isonovalic acid was not consumed. A three main steps metabolic scheme was outlined to explain α-pinene oxide bioconversion into novalic acid. These data enabled to perform an optimized bioconversion of α-pinene oxide into novalic acid in a stirred aerated tank bioreactor in biphasic conditions. Results allowed to obtain c.a. 16 g/L product in about 8 h with a yield close to 40%.