Characterization of monoterpene biotransformation in two pseudomonads

AIMS: To study the metabolic profile of Pseudomonas rhodesiae and Pseudomonas fluorescens in water-organic solvent systems using terpene substrates for both growth and biotransformation processes and to determine the aerobic or anaerobic status of these degradation pathways. MATERIALS AND METHODS: Substrates from pinene (alpha-pinene, alpha-pinene oxide, beta-pinene, beta-pinene oxide, turpentine) and limonene (limonene, limonene-1,2-oxide, orange peel oil) families were tested. For the bioconversion, the terpene-grown biomass was concentrated and used either as whole cells or as a crude enzymatic extract. CONCLUSION: Pseudomonas rhodesiae was the most suitable biocatalyst for the production of isonovalal from alpha-pinene oxide and did not metabolize limonene. Pseudomonas fluorescens was a more versatile micro-organism and metabolized limonene in two different ways. The first (anaerobic, cofactor-independent, noninducible) allowed limonene elimination by synthesizing alpha-terpineol. The second (aerobic, cofactor-dependent) involved limonene-1,2-oxide as an intermediate for energy production through a beta-oxidation process. SIGNIFICANCE AND IMPACT OF THE STUDY: Enzymatic isomerization of beta- to alpha-pinene was described for the first time for both strains. Alpha-terpineol production by P. fluorescens was very efficient and appeared as a promising alternative for the commercial production of this bioflavour.