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BACKGROUND: In recent years, bioprocess development has been used scaled down bioreactors, parallel operation and on-line monitoring. In this study novel miniature bubble column bioreactors (MBCRs) have been developed. Reproducibility of the bioreactors, the effect of operational parameters and scale up to a conventional STR were studied. RESULTS: Fermentations in the parallel MBCRs were reproducible under the same conditions. Increasing the aeration rate had an insufficient effect on the specific growth rate ( ) of E. coli, but it led to an increase in the volumetric mass transfer coefficient (K L a) and evaporation rate. The oxygen uptake rate (OUR) remained constant at different aeration rates as well as . Increasing the temperature resulted in a significant increase in , K L a, evaporation rate and OUR. Control of the pH had a slight but sufficient effect on K L a. Scale up results with an equal K L a demonstrated good agreement between the MBCR and a conventional STR. According to the Damköhler number, the biochemical reaction was rate-limited. CONCLUSION: High achievable K L a in the MBCRs and successful scale-up suggested the present system was an efficient alternative to the stirred or shaken devices for high throughput cultivations.

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