Mushroom-based biocatalysts for the synthesis of aroma and flavours from exogenous organic molecules: a review of two decades

Mushroom species, rich in lignolytic oxidoreductases are promising biocatalysts for the functionalization or degradation of small molecules to produce aroma and/or flavours. These macrofungi, sources of thermostable extracellular enzymes are often safer as biocatalysts, produce aromatic flavours similar to plant-origin and capable of using a wide range of recalcitrant lignocellulosic substrates. The current review summarises the research on mushroom-mediated production of aroma and aromatic flavours from organic molecules (pure or extract) in the last two decades. It mainly includes oxidative conversion or degradation of small molecules such as mono and sesquiterpenoids, phenylpropanoids, aromatic or linear alcohols and carbonyls, alkenes, carotenoids, fatty acids and amino acids into oxygenated aroma/flavours using the whole-cells or purified enzymes of mushroom-origin. Allylic or alcohol oxidation, alkene cleavage and degradation of unsaturated long-chains were the major pathways of oxidative transformations. Reductive conversions of aromatic and linear carbonyls were also exemplified. However, slow biomass growth, low-substrate load, conversion, product titre and selectivity, long fermentation time, difficult/low expression of enzymes, cost-effective and efficient upscaling, insufficient genomic data are major challenges in utilising the diversity of mushroom species for aroma and bioflavour production in industrial scale.