General Forms of Balance Equations

The transport balance part of a mathematical model of a bioreactor consists of mass and energy balance equations. Such an equation expresses how a key system variable changes over time and includes terms that describe various phenomena that affect that variable. Regardless of what the units of the variable of interest are, the balance equation should initially be written in such a way that all of its terms have units of either kg h1, in the case of a mass balance, or J h1, in the case on an...

Heat Transfer Coefficient Of Plastic

20.3.3 Wall-to-Surroundings Heat Transfer Coefficients The wall-to-surroundings heat transfer coefficient (hwsurr J s-1 m-2 C-1) will vary markedly, depending on whether the bioreactor wall is surrounded by air or by the water in a water jacket, and also by the flow of this cooling fluid. In the case of air, the air may be blown forcefully past the bioreactor (forced convection) or not. In the latter case, flow will be due to natural circulation, with heat being removed by natural convection....

Model of the Zymotis Packed Bed Bioreactor

The model described here is based on that developed for the Zymotis bioreactor of Roussos et al. 1993 by Mitchell and von Meien 2000 . The version used here has been modified by the inclusion of a water balance. The model of the Zymotis packed-bed must account for heat transfer in two directions in the substrate bed 1 the direction that is co-linear with the air flow, which causes convective and evaporative heat removal and 2 the horizontal conduction to the cooling plates, which is normal to...

References

Life, the universe and everything. Pan Books, London Agosin E, Aguilera JM 1998 Industrial production of active propagules of Trichoderma for agricultural uses. In Harman GE ed Trichoderma amp Gliocladium, vol. 2. Taylor amp Francis, London, pp 205-227 Ashley VM, Mitchell DA, Howes T 1999 Evaluating strategies for overcoming overheating problems during solid state fermentation in packed bed bioreactors. Biochem Eng J 3 141-150 Figs. 6,7, and 8 adapted with permission from...

Basic Features Design and Operating Variables for Packed Bed Bioreactors

Plafractor

The basic design features of a packed-bed bioreactor have been already presented in Sect. 3.3.1. Figures 7.1 and 7.2 show these features in more detail. Some possible variations in the design include the column may have a cross section other than circular. the column may lie horizontally, or for that matter, at any angle. This alters the relative directions of the forces due to gravity and air pressure. the column may be aerated from either end. For a vertical column, the air may enter the bed...

Screw and Belt Conveyor Bioreactors

Rotating Drum Bioreactor

Screw conveyors and belt conveyors, which are examples of continuous tubular flow bioreactors CTFBs , can move solids with almost zero mixing in the direction of flow Fig. 11.3 . When mixing is desired, which is often the case, static or dynamic mixers can mix the bed in the radial direction and, if desired, also in the axial direction. The current subsection focuses on the situation without axial mixing. Due to lack of back mixing, internal back-inoculation is not possible, however, external...

Convection

Convective cooling, that is, cooling by transfer of heat to a moving fluid, which then transports the heat away due to bulk flow, occurs in various situations in SSF bioreactors that we might like to describe within bioreactor models at the bioreactor wall, the removal of heat to flowing water in a water jacket, or to flowing air, which might either be forcefully agitated or be undergoing natural convection at a bed surface in which there is a cross-flow of air within a forcefully aerated bed,...

Info

Koji Bioreactor

Basic design features of large-scale rotating-drum bioreactors. a Drums used for penicillin production. This is a simplified version of a diagram presented by Ziffer 1988 . b Koji bioreactor. This is a simplified version of a diagram presented by Sato and Sudo 1999 Fig. 8.3. Basic design features of large-scale rotating-drum bioreactors. a Drums used for penicillin production. This is a simplified version of a diagram presented by Ziffer 1988 . b Koji bioreactor. This is a simplified...

The Challenges Faced at Large Scale in SLF and SSF

The major challenge in the scale-up of aerobic submerged liquid fermentation processes is the transfer of O2 into the liquid at a sufficient rate to obtain high cell densities. Scale-up strategies that address this transfer, which is characterized by the parameter kLa, have long been available in the area of SLF Kossen and Oosterhuis 1985 . Although heat transfer calculations must be done, in order to provide sufficient cooling capacity, heat removal is typically not an overly challenging task....

Stirred Beds with Mechanical Agitators

Mechanically Agitated Bioreactor

Some mechanically agitated bioreactors involve a substrate bed that sits on a perforated plate, such that air is blown through the whole cross-section of the bed. A mechanical agitator embedded in the bed mixes the bed. In the case of the 50-L bioreactor of Chamielec et al. 1994 and Bandelier et al. 1997 the bed is mixed with a planetary mixer, that is, the mixer blade rotates around its central axis while this central axis simultaneously rotates around the central axis of the bioreactor Fig....

The General Steps of an SSF Process

Inoculum Preparation For Fermentation

At the most general level, the major processing steps of an SSF process are no different from those of a submerged liquid fermentation SLF process, with which we assume that the reader has a general familiarity. These processing steps include Fig. 2.1 Fig. 2.1. An overview of an SSF process operated in batch mode. Note that the details can vary from process to process. For example, the substrate might either be sterilized within the bioreactor or sterilized before being added. At this level of...

Basic Features of Group IVb Bioreactors

The basic design features of intermittently mixed bioreactors are similar to those of the various continuously mixed designs Chap. 9 , the difference being in the mode of operation. Since the mixing is only intermittent and the bioreactor spends periods in the static mode of operation, designs should be preferred that give a uniform aeration of the bed when it is static. Forced aeration may or may not be applied during the mixing period, depending on the design. Figure 10.1 shows possible basic...

Modeling Case Studies of SSF Bioreactors

After a brief introduction in Chap. 21, Chaps. 22 to 25 present case studies in which fast-solving models are used to explore the design and operation of various SSF bioreactors. These include well-mixed bioreactors with forced aeration Chap. 22 , rotating drum bioreactors Chap. 23 , packed-bed bioreactors Chap. 24 , and intermittently-mixed forcefully-aerated bioreactors Chap. 25 . The case studies ask and answer questions such as What aeration rate will be needed in order to control the bed...

The Bioreactor of PUCChile

P rez-Correa and Agosin 1999 built a bioreactor with a capacity for a bed of 200 kg. The bioreactor has three sections Fig. 10.4 . The bottom section, which remains stationary, is simply the air box. The 150 cm diameter bed is held by the second section, which is rotated in its entirety by a motor. The top of the bioreac-tor represents a third section, which is stationary, and on which the agitators are mounted. The thermocouples can be withdrawn from the bed into the headspace during the...

Bioreactors Mixed by the Motion of the Bioreactor Body

Horizontal Drum Perforat Bioreactor

It is also possible to obtain some mixing within the substrate bed through movement of the whole bioreactor body Fig. 9.6 . A rocking-drum bioreactor of 1.3 L holding volume was used by Barstow et al. 1988 , Ryoo et al. 1991 , and Sargantanis et al. 1993 in studies of bioreactor control strategies. The bioreactor consists of three concentric drums, an inner, a middle, and an outer drum Fig. 9.6 a . The inner drum and the middle drum are perforated, and the substrate bed is held, loosely packed,...

Basic Features Design and Operating Variables for Traytype Bioreactors

Tray Bioreactor For Ssf

Group I bioreactors, or tray bioreactors, represent the simplest technology for SSF. They have been used for many centuries in the production of traditional fermented foods such as tempe and in the production of soy sauce koji. However, this chapter does not review these applications. Readers interested in traditional fermented foods should consult the reading listed at the end of the chapter. The current chapter considers tray bioreactors as candidates in the selection of bioreactors for...

Basic Features Design and Operating Variables for Group III Bioreactors

Rotating Drum Bioreactors

The basic design features have already been presented in Sect. 3.3.1. Some possible design variations include Fig. 8.1 the inclusion of baffles or, more correctly, lifters periodic reversal of the direction of rotation use of drum cross-sections that are not circular inclination of the drum axis to the horizontal. Design variables for both baffled rotating-drum and stirred-drum bioreactors include Fig. 8.2 the length and diameter of the bioreactor. Note that the geometric proportions can vary...

Further Reading

Early studies to elucidate the importance of temperature and gas gradients in packed-bed bioreactors Gowthaman MK, Ghildyal NP, Raghava Rao KSMS, Karanth NG 1993 Interaction of transport resistances with biochemical reaction in packed bed solid state fermenters The effect of gaseous concentration gradients. J Chem Technol Biotechnol 56 233-239 Gowthaman MK, Raghava Rao KSMS, Ghildyal NP, Karanth NG 1993 Gas concentration and temperature gradients in a packed bed solid-state fermentor....

Heat and Mass Transfer in Tray Bioreactors

Depending on the situation, it may be appropriate to consider either an individual tray or the whole-tray chamber as the bioreactor. For example, it would be appropriate to treat the whole tray chamber as the bioreactor when the trays are open to free gas and water exchange with their surroundings and the temperature and humidity of the air in the tray chamber are carefully controlled. The question about optimum design of tray chambers has received little attention. For example, quantitative...

Large Scale Intermittently Mixed Bioreactors 10311 The Koji Industry

Bioreactor Soy Sauce

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...

Using Models to Design and Optimize an SSF Bioreactor

Picture Ssf Bioreactors

Figure 12.2 gives a more detailed view than Fig. 12.1 of how the design process should be carried out for production-scale SSF bioreactors, starting with the necessary laboratory-scale studies and ending with final optimization at large scale. It highlights the fact that it is ideally a process in which experimental and modeling work is undertaken simultaneously, with the mathematical model being refined constantly in the light of experimental evidence. The current section gives a broad...

Macroscale View of the Phases in an SSF Bioreactor

Pictures Ssf Bioreactor

From a macroscale perspective, the bioreactor contains three phases Fig. 2.4 a a headspace full of gas, the extent of which depends on the bioreactor type a substrate bed, composed of particles and air within the inter-particle spaces. The bioreactor wall is important as a barrier. It should be a complete barrier to mass transfer. Matter can only enter the bioreactor through holes in this wall addition ports, sampling ports, loading unloading ports . It is a partial barrier to energy transfer....

Heat Transfer Coefficients Involving the Wall

If the bioreactor wall is not recognized explicitly as a separate phase in the model, then the heat transfer to the surroundings will be described as a direct transfer from the outer surface to the bed to the surroundings Eq. 18.6 in Sect. 18.3.1 . In this case, the various resistances, that is, for transfer from the bed to the wall, transfer across the wall and transfer from the wall to the surroundings, will be lumped together into an overall heat transfer coefficient hov. In cases where the...

Pressure Gradients in Packed Beds

This phenomenon, introduced in Chap. 7.2.4, is of particular importance in packed-beds due to the combination of static operation with forced aeration. The static operation means that the hyphae that grow into the inter-particle spaces are not disrupted or squashed onto the particle surface, and therefore these hyphae represent an extra impediment to air flow, increasing the pressure drop. The maximum pressure drop expected during the fermentation is an important consideration because it will...

Overview of Bioreactor Types

Many different bioreactors have been used in SSF processes, and have been given different names by different authors. However, based on similarities in design and operation, SSF bioreactors can be divided into groups on the basis of how they are mixed and aerated Fig. 3.2 . Group I Bioreactors in which the bed is static, or mixed only very infrequently i.e., once or twice per day and air is circulated around the bed, but not blown forcefully through it. These are often referred to as tray...

Continuous Rotating Drum Bioreactor CRDB

This bioreactor is similar to those of the stirred tank group but differs in the manner in which mixing is achieved the CRDB consists of a cylinder that rotates horizontally around its axis. Bioreactors of this kind fall between perfectly mixed bioreactors and plug-flow bioreactors and hence might be referred to as mixed-flow bioreactors. Indeed, as in solid-drying equipment of this shape see Moyers et al. 1999 , they can have internal devices that promote forward and backward mixing. These...

Fundamentals of Modeling of SSF Bioreactors

Chapters 12 to 20 cover various aspects that are fundamental to an understanding of how to model SSF bioreactors. Chapter 12 starts with an overview of how modeling is undertaken, outlining a series of steps. The first of these steps involves making a decision about what degree of complexity is desired in the model, with more complex models potentially being more useful tools than simpler models, but also requiring much greater effort and sophistication, not only in the formulation and solution...

Interparticle Space

Changes in biomass distribution during a static SSF process with a fungus. a Growth to cover the particle surface during the early phases of the fermentation, shown with an overhead view of the particle surface. b Development of aerial and penetrative hyphae during the fermentation, shown with a side view of a cut through two particles with an air space between them Fig. 2.7. Changes in biomass distribution during a static SSF process with a fungus. a Growth to...

The Seven Steps of Developing a Bioreactor Model

In order to develop a mathematical model for your bioreactor from scratch, you would need to undertake 7 steps Fig. 12.6 . These steps were followed in the development of the various mathematical models presented in Chaps. 22 to 25. Of course, with the availability of these models, it is currently possible to start in the middle of the process. For example, you could use model equations from the literature for the same type of bioreactor and start at Step 4, with the determination of the...

The Bioreactor Step of an SSF Process

Design Bioreactor Ssf

The bioreactor step is a key step in an SSF process. It is in this step that the bioconversion takes place. More details about bioreactor operation will be given later. At this point it is only necessary to understand the general features of a typical SSF bioreactor and how it might be operated Fig. 2.2 . The bioreactor has two important functions to hold the substrate bed and provide a barrier against both the release of the organism to the surroundings and the contamination of the substrate...

Insights from Dynamic Modeling of Trays

No modeling case study will be presented for trays in this book and therefore this section will discuss the insights that dynamic mathematical models of tray biore-actors have given into the relative importance of temperature and O2 limitations in controlling the performance of trays. Rajagopalan and Modak 1994 developed a model to describe heat and mass transfer in trays, which included the various processes shown in Fig. 6.4. They used their model to investigate the relative importance of...

Why Do We Need a Book on the Fundamentals of SSF Bioreactors

So if solid-state fermentation has such potential, why is it not a more widely used technology Why are there relatively few large-scale success stories such as exemplified by the koji step of soy sauce production Of course, part of the problem has already been touched upon in Sect. 1.2 Our inability to control conditions may well put a stress on the organism that causes it to produce a useful product in large quantities however, too much stress may reduce yields and even kill the organism. For...