Abstract
Uncaria tomentosa cell suspension cultures were grown in a 2‐L stirred tank bioreactor operating at a shear rate $\dot \gamma _{\rm avg} = 86,{\rm s}^{ - 1} $. The cultures showed an early monophasic oxidative burst measured as H~2~O~2~ production (2.15 µmol H~2~O~2~ g^−1^ dw). This response was followed by a transient production of monoterpenoid oxindole alkaloids (178 ± 40 µg L^−1^ at 24 h). At the stationary phase (144 h), the increase of the shear rate $\dot \gamma _{{\rm avg}} $ up to 150 s^−1^ and/or oxygen tension up to 85% generated H~2~O~2~, restoring oxindole alkaloid production. U. tomentosa cells cultured in Erlenmeyer flasks also exhibited the monophasic oxidative burst but the H~2~O~2~ production was 16‐fold lower and the alkaloids were not detected. These cells exposed to H~2~O~2~ generated in situ produced oxindole alkaloids reaching a maximum of 234 ± 40 µg L^−1^. A positive correlation was observed between the oxindole alkaloid production and the endogenous H~2~O~2~ level. On the other hand, addition of 1 µM diphenyleneiodonium (NAD(P)H oxidase inhibitor) or 10 µM sodium azide (peroxidases inhibitor) reduced both H~2~O~2~ production and oxindole alkaloids build up, suggesting that these enzymes might play a role in the oxidative burst induced by the hydrodynamic stress. Biotechnol. Bioeng. 2007; 98: 230–238. © 2007 Wiley Periodicals, Inc.