Bioconversion of Citrus Aroma Compounds by Pichia pastoris

After induction of alcohol oxidase, active Pichia pastoris cells were grown in model alcohol solutions and orange aroma, a by-product rich in potential alcohol substrates for bio-oxidation to aldehydes. Acetaldehyde production efficiency was 60% at 0.1% ethanol, decreasing with increasing ethanol. Acetaldehyde, propanal, and octanal were generated using the Pichia system with orange aroma as substrate. Acetaldehyde concentration doubled during a 24h reaction time at 30°C. In contrast to use of isolated alcohol oxidase, the whole cell system had the advantage of cofactor regeneration and associated enzyme systems, including formaldehyde dehydrogenase. Sensory differences were found in the full strength biomodified aroma. Presented in a paired comparison aroma test, to a trained panel it rated higher for the attributes orange character, freshness, and fruitiness than the unmodified control.