佐藤 誠吾

I)
To maximize volumetric productivity, a high cell density cultivation of microorganisms is one of the most effective method. I developed a new pressurable fermentor for high cell density cultivations of recombinant E. coli and a new temperature control system for the production of recombinant hirudin as a thrombin inhibitor.
One of the most serious problems in submerged mycelial process is the very high non-Newtonian viscosity of fermentation broths. This is associated with the growth of mycelial organisms in a highly extended and branched filamentous form. I have studied several important factors (viscosity, oxygen transfer coefficient and diffusion coefficient) affecting on the fermentation of the polyelectrolyte complex immobilized A. niger cells at a very high cell concentration (40g/ℓ), at which a marked enhancement in the gluconic acid production was observed.

II)
The new sterilization methods have been required in fermentation and food industries. My research project in this field is to clarify the mechanism of microwave sterilization and to develop high speed sterilization using the microwaves. The wavelength of the microwaves for heating is about 12cm, whereas the sizes of microbial cells are micro-meters. After several studies, I have clarified that the microwaves were not absorbed by microbial cells, since the cell sizes are too small, but they were absorbed in only water. I have concluded that the mechanism of microwave sterilization is the temperature rise of water surrounding microbial cells.