Hydrodynamic stress induces monoterpenoid oxindole alkaloid accumulation by Uncaria tomentosa (Willd) D. C. cell suspension cultures via oxidative burst

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.