Fig 5.
Biotransformation of ferulic acid by Amycolatopsis sp. ATCC 39116 and the Amycolatopsis sp. ATCC 39116 Δvdh::Kmr mutant. Cells were grown in 250 ml Caso medium at 42°C and harvested during the stationary growth phase. After two wash steps with phosphate-buffered saline (pH 7.5), cells were resuspended in 1,000 ml of the same buffer containing 2 mM ferulic acid. The cultures were incubated in a 2-liter bioreactor at 42°C for 30 h. The biotransformation of ferulic acid (A) to vanillin (B) and vanillic acid (C) was observed at the given times by using HPLC analyses, as described in Materials and Methods. Initially, ferulic acid was fed at a rate of 0.75 mM/h during the first 7 h. Afterwards, substrate was fed for 3 h at a rate of 3.1 mM/h, before feeding was stopped. ▲, Amycolatopsis sp. ATCC 39116; ●, Amycolatopsis sp. ATCC 39116 Δvdh::Kmr mutant.