Improvement of ferulic acid bioconversion into vanillin by use of high-density cultures of Pycnoporus cinnabarinus

High-density cultures of Pycnoporus cinnabarinus were tested with a view to optimisation of ferulic acid bioconversion into vanillin. The dry weight was increased fourfold by using glucose, fructose or a mixture of glucose and phospholipids as carbon source instead of maltose, the carbon source previously used. 5 mmol l⁻¹ vanillin, i.e. 760 mg l⁻¹, was produced over 15 days with glucose-phospholipid medium. In contrast, formation of vanillin was lower using glucose or fructose compared to the maltose control. A bioreactor (2 l) with a glucose-phospholipid medium gave a molar yield of vanillin of 61% (4 mmol l⁻¹). An alternative strategy was to grow the fungus on a glucose or fructose medium for 3 days, then switch to maltose during the bioconversion phase: this method allowed 3.3 mmol l⁻¹ vanillin to be obtained in 10 days. Many by-products such as methoxyhydroquinone and vanillyl alcohol were also produced. Received: 19 February 1999 / Received revision: 4 June 1999 / Accepted: 4 June 1999