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Bioconversion of limonene to alpha-terpineol by immobilized Penicillium digitatum

Tan, Q., Day, D.F.
Applied microbiology and biotechnology 1998 v.49 no.1 pp. 96-101
Penicillium digitatum, aeration, alpha-terpineol, biotransformation, calcium alginate, dissolved oxygen, fungi, half life, limonene, mycelium
Bioconversion of (4R)-(+)-limonene to (4R)-(+)-alpha-terpineol by immobilized fungal mycelia of Penicillium digitatum was investigated in batch, repeated-batch and continuously fed systems. The fungi were immobilized in calcium alginate beads. These beads remained active for at least 14 days when they were stored at 4 degrees C. Three different aeration rates were tested. The highest yield was obtained at a dissolved oxygen level of 50.0 micromol/l. alpha-Terpineol production by this fungus was 12.83 mg (g beads)-1 day-1, producing a 45.81% bioconversion of substrate. Repeated-batch bioconversion showed yield decreases in the second and the third cycles. Regeneration with nutrient media after the third cycle improved the bioconversion yields. With continuous bioconversion, the half-life was dependent on the aeration. The optimum conditions with a continuous reactor were at an aeration rate of 0.3 standard 1/min and a dilution rate of 0.0144 h-1.