Mushroom-Mediated Reductive Bioconversion of Aldehyde-Rich Essential Oils for Aroma Alteration: A Rose-like Floral Bioflavor from Citronella Oil.

ABSTRACT

The bioflavors are of high demand in food and beverage industries. The current study identified reductive processes mediated by mushroom species to alter the aroma of aldehyde-rich essential oils in the submerged culture. Neofomitella polyzonata, a polypore mushroom, reduced citronellal and citral in the citronella oil into corresponding alcohols that altered the oil aroma, creating a new bioflavor. The screening with 43 aldehydes showed its broad substrate scope within aromatic and linear aldehydes, yet influenced by the electronic and steric factors. Under an optimized condition, it efficiently converted up to 1.5 g/L citrusy and sharp citronella oil into a terpene alcohol-rich (citronellol and geraniol) floral, sweet, fresh, and rosy oily product within 12 h. The preparative-scale fermentation in the shake flask followed by distillation, an organic solvent-free downstream process, furnished the product in 87.2% w/w yield. Detailed sensory analyses and volatile chemo-profiling established the uniqueness in the product aroma and identified citronellol and geraniol as the key odorants. The chemometric analysis found best compositional similarity of this product with Damask or Turkish rose oils. The preference test for the water flavored with the fermented product (0.001-0.005% v/v) indicated its potential as a rosy bioflavor for the beverages.