Radiation Sterilization of Fermentation Raw Materials:Part 1. The effects of cathode ray irradiation on the media for isomerase producing Streptomyces
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When pentoses in the fermentation media are heated in the presence of nitrogen compounds, the media are heavily browned and the growth of microorganisms in such a medium is sometimes inhibited. Therefore it is necessary as usual to sterilize pentose and nitrogen compound separately. This paper concerned with the so-called "cold sterilization" of the fermentation medium in order to avoid such a browning and denaturation due to heat treatment, and the effects of cathode ray irradiation on the medium for Streptomyces phaeochromogenus which produced glucose isomerase when grown on the medium containing xylose were investigated.<BR>The media were sterilized by five different methods as shown in Table 1 and for radio sterilization 1 MeV Van de Graaff electron accelerator was used. Different methods of sterilization resulted in different growth of the microorganism in the initial stage of propagation. The growth in the radiation sterilized medium was considerably inferior comparing with the growth in the separately autoclaved or aseptically filtered medium as shown in Fig. 1. However the inhibitory effect of radio-sterilized medium in the initial growth stage was eliminated during the propagation of over night shaking and after 24 hours cell yield and isomerase activity were determined as equal as the result by the usual autoclaved medium (Table 3-II). Accordingly it seems to be possible to adopt the cold sterilization on the isomerase production medium.<BR>The growth inhibition in the initial stage of propagation was found to be remarkable in the radiosterilized medium with acidic pH and less in the medium with neutral or alkaline side pH. Cystein was added to prevent the occurrence of anti-growth factor but there was not a noticeable effect.
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