Continuous-sterilization system that uses photosemiconductor powders.

We report a novel photochemical sterilization system in which Escherichia coli cells were sterilized with photosemiconductor powders (titanium oxide). For sterilization that could be used in practice, it was necessary to separate the TiO2 powders from the cell suspension. Therefore, semiconductor powders were immobilized on acetylcellulose membranes. We constructed a continuous-sterilization system consisting of a TiO2-immobilized acetylcellulose membrane reactor, a mercury lamp, and a masterflex pump. As a result, under the various sterilization conditions examined, E. coli (10(2) cells per ml) was sterilized to less than 1% survival when the cell suspension flowed in this system at a mean residence time of 16.0 min under irradiation (1,800 microeinsteins/m2 per s). We found that this system was reusable.