Catabolism of branched chain and aromatic amino transferases, route to fusel alcohols and acetates by the Ceratocystidaceae.

Dineo Mailula,Magriet Van Der Nest,Brenda Wingfield,Almuth Hammerbacher,Nokuthula Mchunu

doi:10.3390/ecm2020-07097

Dineo Mailula, Magriet Van Der Nest + Show 3 more

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https://doi.org/10.3390/ecm2020-07097

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Abstract

Fungi in the family Ceratocystidaceae produce fusel alcohols and acetates that have fruity and floral odours. Since fusel alcohols are produced in fungi from amino acids via the Ehrlich pathway in a three-step catabolic process, we identified and characterized the genes encoding enzymes involved in catalysing the first and second steps in this pathway. We identified three putative branched-chain amino transferases, three putative aromatic amino transferases and a putative pyruvate decarboxylase in each of the Bretziella, Berkeleyomyces, Ceratocystis, Davidsoniella, Endoconidiophora, Huntiella and Thielaviopsis genomes. Using gas chromatography coupled to mass spectrometry (GC-MS), also revealed that all the strains included in this study produced high levels of isoamyl acetate. In contrast, only some members of Bretziella, Berkeleyomyces, Ceratocystis and Huntiella produced isobutyl acetate, while only the Berkeleyomyces, Ceratocystis and Huntiella strains produced 2-phenylethyl acetate in low quantities. Either by accepting the branched-chain amino acid substrates (valine and leucine) or accepting the aromatic amino acid substrate (phenylalanine). Fusel alcohols and acetates produced by fungi in the Ceratocystidaceae can therefore be used as additives of food products, perfumes and soaps. In addition, identified fusel alcohols can potentially be utilized as biofuels or biodiesels, bringing solutions to the problems associated with limited fossil resources and climate change.

Highlights

Fusel alcohols and acetates are volatile chemical compounds that are widely used in food, cosmetic, pharmaceutical and biofuel industries (Fig. 1 and Table 1) (Hua & Xu, 2011)
Our findings showed that fungi in the Ceratocystidaceae produced fruity, banana or floral scents consisting of mixtures of volatile chemical compounds, including fusel alcohols and acetates
We showed that the genomes of fungi in the Ceratocystidaceae contain three functional branched chain amino transferase (BAT1) enzymes which catalyse the first step in aliphatic fusel alcohol biosynthesis

Summary

Introduction

Fusel alcohols and acetates are volatile chemical compounds that are widely used in food, cosmetic, pharmaceutical and biofuel industries (Fig. 1 and Table 1) (Hua & Xu, 2011). They play an essential role in the flavouring of food and drinks (Welsh et al, 1989, Mauricio et al, 2001, Etschmann et al, 2002), as well as fragrance modification of cosmetic products like perfumes and soaps (Welsh et al, 1989, Branduardi et al, 2013). The branched chain fusel alcohols include isobutanol, 3-methyl butanol (isoamyl alcohol) and 2-methyl butanol while 2-phenylethanol is the most well-known and used aromatic fusel alcohol Both branched chain and aromatic fusel alcohols and acetates can be produced artificially through chemical synthesis or naturally by plants and microorganisms (Spinnler & Djian, 1991, Goettmann et al, 2006, Hazelwood et al, 2008).

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