ABSTRACT
A two-step bioconversion process of ferulic acid to vanillin was elaborated combining two filamentous fungi, Aspergillus niger and Pycnoporus cinnabarinus. In the first step, A. niger transformed ferulic acid to vanillic acid and in the second step vanillic acid was reduced to vanillin by P. cinnabarinus. Ferulic acid metabolism by A. niger occurred essentially via the propenoic chain degradation to lead to vanillic acid, which was subsequently decarboxylated to methoxyhydroquinone. In 3-day-old cultures of P. cinnabarinus supplied with vanillic-acid-enriched culture medium from A. niger as precursor source, vanillin was successfully produced. In order to improve the yields of the process, sequential additions of precursors were performed. Vanillic acid production by A. niger from ferulic acid reached 920 mg1-1 with a molar yield of 88% and vanillin production by P. cinnabarinus from vanillic acid attained 237 mg1-1 with a molar yield of 22%. However, the vanillic acid oxidative system producing methoxyhydroquinone was predominant in P. cinnabarinus cultures, which explained the relatively low level in vanillin.
Subject(s)
Aspergillus niger/metabolism , Benzaldehydes/metabolism , Coumaric Acids/metabolism , Polyporaceae/metabolism , Biotechnology/methods , Biotransformation , Kinetics , Oxidation-Reduction , Vanillic Acid/metabolismABSTRACT
In extracts obtained by liquid-liquid extraction and enzymatic hydrolysis from five apple cultivars (Renao; Bedan; Peau de Chien; Noel des Champs; Red Delicious), chiral evaluation of free and glycosidically-bound octane-1,3-diol and 5(Z)-octene-1,3-diol, as well as ethyl 3-hydroxyoctanoate and ethyl 5(Z)-3-hydroxyoctenoate, was performed by multidimensional gas chromatography (MDGC), combining a polar achiral column (DB-Wax) with a chiral main column (2,3-di-O-acetyl-6-O-tert. butyldimethylsilyl-beta-cyclodextrin/OV 1701). Comparison of retention times of synthesized optically-enriched reference compounds with isolated diols and hydroxyesters, revealed the (R)-configuration for the free diols in cvs. Renao, Bedan, Peau de Chien and Noel des Champs and the (R)-configuration for the bound diols in cvs Bedan, Peau de Chien and Noel des Champs, exhibiting enantiomeric excesses (ees) greater than 99%. (R)-hydroxyesters (ee > 99%) were detected in cvs. Noel des Champs and Red Delicious.
