Josef Metze

Generation of larger numbers of separated microbial populations by cultivation in segmented-flow microdevices

The high speed production of fluid segments for the highly parallelized cultivation of monoclonal cell populations was carried out by the use of microchip segmentor modules. Aqueous fluid segments, embedded in a non-miscible carrier liquid, were produced with frequencies up to 30 s(-1) and showed a high homogeneity in size. This corresponds with the production of about 2.5 million samples per day. The segment volumes can be adapted between about 4 nl and 100 nl. The typical segment size for cultivation experiments is in the range between 40 nl and 80 nl. Nutrient medium can be applied instead of pure water. It is possible to aliquot a cell suspension in such a way that most of the aqueous fluid segments contain only one cell. In model experiments with four microbial species chip-produced aliquots of 60 nl, each containing one or a few cells, were incubated in Teflon capillary tubes. Rapid growth of the microcultures was observed. Cell densities were found to be as high as in conventional shake flask cultures.

Hydrodynamic influence on sampling systems in bioreactors

A special challenge for bioprocess technology has been interfacing new analytical equipment to the bioreactor. The main component of this interface is a sterile barrier between the biological process and the monitoring system. The connecting link is a sampling unit with micro- or ultrafiltration membranes. In order to prevent biofouling on top of the membranes, we have developed an oscillating sampling system. A model can describe the hydrodynamics, and the distribution forces in the region between membrane and medium. We compare a static sampling device to an oscillating one during a yeast cultivation process, with regard to filtration rates and the analysis of the withdrawn samples via Scanning Electron Microscopy (SEM) and Fourier Transformed Infrared Spectroscopy (FTIR). The results indicate that the oscillating sampling device shows better sampling flow behaviour.

Cell Cultivation System on the Basis of Porous Ceramic for the Production of Virus-Like Particles

The production of virus-lilce particles (VLP) is based on the expression of human Polyomavirus (JCV)-VP1 in anchorage-dependent insect cells SF-158 using recombinant baculoviruses. To use these VLPs in future in clinical trials as an efficient delivery system for gene therapy it is necessary to establish a large scale production. For this purpose a new cultivation system basing on the attachment of cells onto macroporous ceramic in a special flow chamber was developed. On these ceramics insect cells form multicellular monolayers. During cell growth and baculovirus infection cells were fed with aerated, tempered and pH-controlled medium from a reservoir. The process is monitored by measuring the oxygen consumption (online), the glucose consumption and viable cell counts (both: offline). Testing two different flow chambers with fitting ceramics, one squared ceramic and one cylindrical honeycomed ceramic with a corresponding larger growth surface, the optimal medium flow, the doubling time and the attachment of the cells were determined. The cells grew in this cultivation system as well as in cell culture flasks and the surface correlated productivity increased approximately eighty-fold.