0 avis
A New Phenolic Acid Decarboxylase from the Brown-Rot Fungus Neolentinus lepideus Natively Decarboxylates Biosourced Sinapic Acid into Canolol, a Bioactive Phenolic Compound
Archive ouverte
International audience. Rapeseed meal (RSM) is a cheap, abundant and renewable feedstock, whose biorefineryis a current challenge for the sustainability of the oilseed sector. RSM is rich in sinapic acid (SA), ap-hydroxycinnamic acid that can be decarboxylated into canolol (2,6-dimethoxy-4-vinylphenol), avaluable bioactive compound. Microbial phenolic acid decarboxylases (PADs), mainly described forthe non-oxidative decarboxylation of ferulic and p-coumaric acids, remain very poorly documentedto date, for SA decarboxylation. The species Neolentinus lepideus has previously been shown tobiotransform SA into canolol in vivo, but the enzyme responsible for bioconversion of the acidhas never been characterized. In this study, we purified and characterized a new PAD from thecanolol-overproducing strain N. lepideus BRFM15. Proteomic analysis highlighted a sole PAD-typeprotein sequence in the intracellular proteome of the strain. The native enzyme (NlePAD) displayedan unusual outstanding activity for decarboxylating SA (Vmax of 600 U.mg−1, kcat of 6.3 s−1 andkcat/KM of 1.6 s−1.mM−1). We showed that NlePAD (a homodimer of 2 × 22 kDa) is fully active in apH range of 5.5–7.5 and a temperature range of 30–55 ◦C, with optima of pH 6–6.5 and 37–45 ◦C, andis highly stable at 4 ◦C and pH 6–8. Relative ratios of specific activities on ferulic, sinapic, p-coumaricand caffeic acids, respectively, were 100:24.9:13.4:3.9. The enzyme demonstrated in vitro effectivenessas a biocatalyst for the synthesis of canolol in aqueous medium from commercial SA, with a molaryield of 92%. Then, we developed processes to biotransform naturally-occurring SA from RSMinto canolol by combining the complementary potentialities of an Aspergillus niger feruloyl esterasetype-A, which is able to release free SA from the raw meal by hydrolyzing its conjugated forms, andNlePAD, in aqueous medium and mild conditions. NlePAD decarboxylation of biobased SA led to anoverall yield of 1.6–3.8 mg canolol per gram of initial meal. Besides being the first characterizationof a fungal PAD able to decarboxylate SA, this report shows that NlePAD is very promising as newbiotechnological tool to generate biobased vinylphenols of industrial interest (especially canolol) asvaluable platform chemicals for health, nutrition, cosmetics and green chemistry.
Consulter en ligne
Suggestions
Du même auteur
