Drum bioreactors

Flower [25], Panda et al. [26], Doran [27]. and Payne et al. [28]. Several kinds of bioreactors, such as the stirred tank bioreactor with hollow paddle and flat blade impellers, the bubble column, the airlift bioreactor with internal and external loops, the rotating drum bioreactor, the stirred-tank with a draft tube, and the mist bioreactor have been attempted for plant cell, tissue and organ cultures (Fig. 1). 

Figure 21. Schematic diagram of the rotating drum bioreactor (Tanaka, H., et al., 1983)...

Fig. 3 (a) Drum bioreactor (7) substrate chamber, (2) loading port, (i) jacket, (4) paddles, (5) central axis, (6) motor, (7) gear box, (S) water inlet, (9) water outlet (70) air inlet, (77) air outlet, (72) product, (b) Packed bed bioreactor (7) water-bath where humidification occurs, (2) air inlet, (3,77) air filter, (4) sparger, (5) water input, (6) water filter, (7) heating coil, (S) basket with perforated bottom, (9) temperature probe for humidified air, (70) medium temperature probe (72) air output, (73) controller and recorder, (77) relative humidity regulator (7), temperature regulator, (A) airflow meter (W) water supply... 

Four basic types of SSF bioreactors have been developed (Figs. 3 and 4). These are (1) drum bioreactor [16], (2) packed bed bioreactor [17,18], (3) tray bioreactor [4, 16], (Ahmed et al. 1987 Hesseltme 1987 Pandey 1991 cited in [19]), and (4) column bioreactor (Raimbault and Germon 1976 cited in [20]). The structure and nature of the solid matrix used, type of microorganism involved, environmental conditions needed for the process, the type of use (research or industrial applications), and type of product should all be considered for the selection of appropriate design of bioreactor [19]. 

The introduction of the koji process to the West is chiefly due to the work of Takamine, which started in 1891 in the USA using wheat bran to make the preparation named Taka-Koji. Takamine introduced the technique of acclimatizing the mold to various antiseptics in order to minimize growth of contaminants during the process. The process was carried out on an industrial scale in rotating drum bioreactors. Large scale trials of the use of Taka-Koji instead of malt in distilleries were carried out in the plant of Hiram Walker Sons in Ontario Canada in 1913. This was marketed as a digestive aid imder the name of Takadiastase [8]. 

Fig. 5. The various bioreactors used in aerobic solid-state fermentations, categorized according to their aeration and mixing characteristics. Note that the drum bioreactors are all cylindrical drums lying horizontally. The bed bioreactors are typically upright cylinders, although they may have other shapes. The air flow in the system is indicated by the dotted lines...

Fig. 8. Heat and mass transfer processes in a rotating drum bioreactor [146]. (1) Entry of sensible energy in inlet air (2) Release of waste metabolic heat by the microorganism (3) Convective heat transfer from the substrate bed to the headspace (4) Evaporation of water from the bed to the headspace, carrying with it the heat of vaporization (5) Conduction from the bed to the drum wall (6) Convective cooling of the drum wall by the headspace gases (7) Convection to the surrounding air (8) Exit of sensible energy in the outlet air (9) The substrate bed is assumed to be well mixed (10) The headspace gases are assumed to be well mixed (11) The high thermal conductivity of the drum wall is assumed to lead to thermal homogeneity...

Discontinuous agitation of rotating drum bioreactors has been used in a few studies [152, 153]. In the work of de Reu et al. [152], when the temperature within the bed exceeded a setpoint, a one-minute agitation regime was initiated, with rotation alternately clockwise and counterclockwise at 4-6 rpm. In different fermentations adequate temperature control was achieved with mixing events being initiated at intervals from as short as 9 min to as long as 142 min. 

The rocking drum bioreactor has some similarities with a packed bed in that the air flowing radially outwards is like the air flowing axially within a packed bed. An advantage of the rocking drum reactor over the packed bed is that water can be replenished reasonably evenly with a reasonably gentle mixing action [107]. 

The work done to date with rocking drum bioreactors has addressed the question of automatic control of SSF bioreactors. Barstow et al. [162] used a control scheme where the air flowrate was increased from 6.2 lmin to 8.5 Imin" whenever the temperature exceeded the set point of 37 °C, and between 9 h and 43 h of fermentation the inlet air was dry. Ryoo et al. [163] pointed out that finer control could be achieved by mixing dry and wet air to achieve the desired relative humidity at a constant overall air flowrate. They managed to maintain the fermentation temperature within 0.5 °C of the set point. However, this work was done in a bioreactor with a holding volume of only 1.3 1, and it is difficult to say how well the bioreactor will operate on a large scale. 

A similar approach applied to rotating drum bioreactors gives a dimensionless design factor [167] ... 

In SSF, several parameters such as particle size, moisture content, incubation time, initial pH, and the amount of nitrogen sources have been shown to be important factors affecting the fungal growth and chitosan production (Nwe and Stevens 2004). An important aspect related to the production of chitosan in SSF has been use of different kinds of laboratory model bioreactors including Erlenmeyer flasks, rotary drum bioreactors, roux bottles, trays, and glass columns to evaluate... 

FIGURE 13 Rotating drum bioreactor for submerged culture. 

The heterogeneity of the system is also reduced to a large extent compared to static trays or a packed-bed fermenter. A rotating drum bioreactor was used by Tao et al. [31] for cellulase production, and the original paper can be referred to for a schematic diagram, where the air compressor, pressure regulation valve, air filter, air heater, atomizer, rotating device, fermenter stand, gas valve, air outlet, thermistor position, and other details are shown. 

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