A two-step bioconversion process for vanillin production from ferulic acid combining Aspergillus niger and Pycnoporus...

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.