Takamine (1914) developed a process for the production of amylase by Aspergillus oryzae on wheat bran, first in tray bioreactors and then later in rotating-drum bioreactors. This work was later extended by Underkofler et al. (1939). Ziffer (1988) was involved in work during the early 1940s in which penicillin was produced at commercial scale by SSF of wheat bran, in a plant containing 40 rotating-drum bioreactors of 1.22 m diameter and 11.28 m length, meaning that each biore-actor had a total volume of 13 m3 (Fig. 8.3(a)). He described how the system was operated, but not how it performed.
The bran was mixed with the nutrient solution externally and then added through the access hatches. These were closed and the bioreactor was sterilized by direct injection of steam, at 1 atm above ambient pressure, while being rotated at 24 rpm. Inoculum was added through spray nozzles, while the drum was rotating at 24 rpm. The aeration rate was maintained between 0.28 and 0.42 m3 min-1
until 30 h, then it was increased to 1.13 m3 min-1, which was maintained until the end of the fermentation. The rotation rate was maintained at 24 rpm during the first 6 h. It was reduced to 5 rpm between 6 and 30 h and then increased to 24 rpm, which was maintained until the end of the fermentation. Water was sprayed onto the external surface in order to aid temperature control. At the end of the fermentation (112 h), the fermented substrate was removed through the access hatches by a pneumatic vacuum system.
Rotating-drum bioreactors have also been used in the koji industry. Sato and Sudo (1999) report the use of a rotating-drum bioreactor of 1500 kg capacity, which is designed to rotate intermittently (Fig. 8.3(b)). They report that accurate temperature control is difficult in this type of bioreactor, but provide no details.
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