To investigate the stability of NeuNAc in cell-free extracts of the recombinant strain, according cell-free extracts obtained from the cultivation in a bioreactor on chitin (vide infra) were spiked with NeuNAc and incubated for 24 h. As a control, a heat-inactivated cell-free extract was similarly treated. Using HPLC analysis after derivatization with DMB, similar amounts of NeuNAc were detected in both extract preparations (Figure 3c) , suggesting that components of the cell-free extract do not actively degrade NeuNAc. In addition, a similar amount of NeuNAc was measured in a NeuNAc-spiked cell-free extract of the recombinant strain that was not incubated, assuming that the 24-h incubation period at 30°C did not decrease the NeuNAc levels. As a final control, a cell-free extract without NeuNAc was also analyzed after a 24-h incubation period and, as expected, showed a lower amount of NeuNAc, which could only have resulted from its formation during the cultivation on chitin. In summary, we did not observe degradation of NeuNAc by H. jecorina. These data suggest that NeuNAc is not metabolized by the recombinant Hypocrea strain.