Optimisation of α-terpineol production by limonene biotransformation using Penicillium digitatum DSM 62840

BACKGROUND: In this study, (R)-(+)-limonene biotransformation using three fungal strains was compared. Penicillium digitatum DSM 62840 was distinguished for its capacity to transform limonene into alpha-terpineol with high regioselectivity. Growth kinetics in submerged liquid culture and the effects of growth phase and contact time on biotransformation were studied using this strain. Substrate concentration, co-solvent selection, and cultivation conditions were subsequently optimised. RESULTS: The maximum concentration of alpha-terpineol (833.93 mg L-1) was obtained when the pre-culture medium was in mediumlog-phaseby adding 840 mg L-1 substrate dissolved in ethanol and cultivation was performed at 24 degrees C, 150 rpm, and pH 6.0 for 12 h. Addition of small amounts of (R)-(+)-limonene (84 mg L-1) at the start of fungal log-phase growth yielded a 1.5-fold yield of alpha-terpineol, indicating that the enzyme was inducible. CONCLUSION: Among these three strains tested, P. digitatum DSM 62840 was proved to be an efficient biocatalyst to transform (R)-(+)-limonene to alpha-terpineol. Further studies revealed that the optimal growth phase for biotransformation was in the medium log phase of this strain. The biotransformation represented a wide tolerance of temperature; alpha-terpineol concentration underwent no significant change at 8-32 degrees C. The biotransformation could also be performed using resting cells. (C) 2015 Society of Chemical Industry