Abstract
A genetically modified strain of Pichia pastoris, which is the methylotrophic budding yeast widely used as a host for the study of secretion, was used in this experiment. The P.pastoris mutants that express human DNase I and secret its product were constructed. First, genetically modified cells were cultured in an Erlenmeyer flask to determine cell-cycle characteristics. The mean generation time was 3.4 h. Second, further cell-cycle analysis was made for the cells in the synchronous culture, which followed hydroxyurea treatment. The time between the hydroxyurea-acting point in and the point of cell division was found to be 1.3 h. Then, a micron-size bioreactor, that is made of an 8cm × 8cm acrylic plate and has a microchannel, which is 500 µm in width, 500 µm in depth and 5671 mm in length, was constructed. Finally, the DNaseI activities of the supernatant in the synchronous culture in the flask and in an experiment using the micron-size bioreactor were compared. DNaseI activities were detected after 4 h in the flask but not detected in the experiment using micron-size bioreactor during 5 h culture time.
