Microscale and miniscale fermentation and screening.

Small-scale bioreactors in the microliter and milliliter range gained more importance in recent years. For the characterization of mass transfer, the volumetric mass transfer coefficient kLa and the oxygen transfer rate OTRmax are considered. kLa values up to 1440 hour(-1) are reported for small-scale bioreactors. The OTRmax is strongly influenced by the liquid film thickness and, finally, by the liquid viscosity. Optical on-line methods, such as fluorescence and scattered light measurements, are applied to monitor pH, dissolved oxygen tension (DOT), product formation and biomass. Recently, single cell microfluidics are used to obtain new insights into microbial behavior at changing operating conditions. Finally, novel fed-batch techniques are applied to assimilate the cultivation conditions between screening and production scale.