Large Scale Intermittently Mixed Bioreactors 10311 The Koji Industry

Intermittently agitated designs have been used in the koji industry. Sato and Sudo (1999) report a bioreactor with a capacity of 15 tons of rice koji on a 12-m diameter disk (Fig. 10.2). The inoculated substrate is placed in the upper chamber, where it remains for one day. After this period the screw mixer is used to transfer the substrate to the bottom chamber, where it is mixed intermittently. The bioreactor is computer controlled. However, Sato and Sudo (1999) give no further details. For example, it is not clear exactly how often the mixing is carried out.

Interestingly, Sato and Sudo (1999) note that, even for an industry with much experience, the maximum height of the substrate bed is of the order of 20 cm. This means that large-scale bioreactors will occupy a large area. The 15-ton capacity bioreactor has disks of 12 m diameter. In comparison, an SLF bioreactor would have a diameter of about 5 m to hold the same working volume, assuming that the solid bed has a packing density of 400 kg m-3 and therefore a volume of 37.5 m3 and that the SLF bioreactor has a height to diameter ratio of 2:1.

Bioreactor Soy Sauce

Fig. 10.2. Intermittently-mixed bioreactor of the type used in the koji industry for soy sauce production by Nagata Brewing Industry Co Ltd., Takarazuka, Japan. It has a 12 m diameter bed and a capacity for 15 tons of substrate. After one day the upper disk is rotated, with the upper screw conveyer transferring the substrate to the lower disk, where it can be agitated intermittently. Note that the mixers rotate in place and the whole circular bed moves to bring the substrate to the mixing point. This is a simplified version of a diagram presented by Sato and Sudo (1999)

Fig. 10.2. Intermittently-mixed bioreactor of the type used in the koji industry for soy sauce production by Nagata Brewing Industry Co Ltd., Takarazuka, Japan. It has a 12 m diameter bed and a capacity for 15 tons of substrate. After one day the upper disk is rotated, with the upper screw conveyer transferring the substrate to the lower disk, where it can be agitated intermittently. Note that the mixers rotate in place and the whole circular bed moves to bring the substrate to the mixing point. This is a simplified version of a diagram presented by Sato and Sudo (1999)

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