BACKGROUNDIn 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. RESULTSFermentations 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 Damkohler number, the biochemical reaction was rate-limited. CONCLUSIONHigh 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. (c) 2014 Society of Chemical Industry