The Increasing Importance of SSF
Solid-state fermentation will become of ever increasing importance. The need to use rationally the organic solid wastes that we generate will increase as the increasing world population puts increasing pressure on environmental resources. In the same manner as the world is coming to understand that, in dealing with liquid wastes, dilution is NOT the solution to pollution, in the case of organic solid wastes, we can say even if it does not rhyme so well that land-filling or disposal in the...
Screw and Belt Conveyor Bioreactors
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...
The Bioreactor Step of an SSF Process
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...
Air Sterilization
The selection of an appropriate filter type will be based on considerations of minimizing the pressure drop for a desired air flow rate while removing very small particles. It may also be influenced by the types of filters that local suppliers actually have available. At laboratory scale, contamination is typically somewhat easier to control while at large scale sterilization and prevention of contamination is more complicated. In fact, contamination may be one of the most frequent operational...
Uniformity of the Product from Batch and Continuous Bioreactors
Continuous operation permits a more uniform product than batch operation, especially in cases in which the solid bed is mixed only intermittently. This can be seen by comparing an intermittently-mixed, forcefully-aerated bioreactor operated in batch mode with the same bioreactor type operated in continuous mode. Note that, as shown in Fig. 11.5, in both bioreactors the air flow is perpendicular to the flow of solids. As described in Chap. 10, this design has been successfully proven in batch...
Why Do We Need Automatic Control in SSF Bioreactors
Here, we will discuss what is important to control in SSF bioreactors and how it can be done. The simulations at the end of this chapter show that performance of SSF bioreactors will be better with control schemes for example, when the temperature in the inlet air is decreased in response to a rise in the average temperature in the bed, or when water is added in response to a drop in the humidity of the off-gases. As with classical submerged liquid fermentation, in SSF processes there is an...
Contributing Authors
Department of Chemical and Bioprocess Engineering Pontificia Universidad Cat lica de Chile P.O. Box 306, Santiago 22, Post Code 6904411, Chile E-mail agosin ing.puc.cl Department of Chemical, Biochemical and Environmental Engineering Faculty of Chemistry and Chemical Technology, University of Ljubljana Askerceva 9, Ljubljana 1000, Slovenia E-mail marin.berovic Uni-Lj.si Deparment of Sciences and Engineering, Universidad de Talca Camino Los Niches km 1, Curic , Chile E-mail mafernandez utalca.cl...
Present State and Future Prospects
It is clear that SSF is not a simple technology. In order for large-scale bioreactors to operate efficiently, we need to base their design and operation on engineering principles. We hope that we have convinced readers of this book that mathematical models of bioreactor operation will be important tools in the design and optimization of performance of large-scale SSF bioreactors. It will also be necessary to extend process control theory to deal adequately with the many complexities that SSF...
An Overview of the Options Available
The air stream not only must be supplied at proper conditions of temperature and humidity as addressed above, it also must overcome the pressure drop caused by the bed, piping, and other accessories. All these aims have to be achieved at low cost, since many SSF processes have low profit margins. At this point, we can examine some alternatives for air preparation, starting with the very simple alternative presented in Fig. 29.1. The system presented in Fig. 29.1 will only be appropriate if...
A Model of the Zymotis PackedBed 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...
Further Reading Ozj
Studies of heat and mass transfer in rotating-drum bioreactors Fung CJ, Mitchell DA 1995 Baffles increase performance of solid-state fermentation in rotating drums. Biotechnol Techniques 9 295-298 Hardin MT, Howes T, Mitchell DA 2001 . Residence time distribution of gas flowing through rotating drum bioreactors. Biotechnol Bioeng 74 145-153 Hardin MT, Howes T, Mitchell DA 2002 Mass transfer correlations for rotating drum bioreactors. J Biotechnol 97 89-101 Schutyser MAI, Weber FJ, Briels WJ,...
The Bioreactor of INRADijon
Durand and Chereau 1988 developed an intermittently mixed bioreactor at INRA, in Dijon, France. It is 2 m long, 0.8 m wide and has an overall height of 2.3 m, with a working bed height of 1 m. This gives a working volume of approximately 1.8 m3, sufficient to hold a bed of approximately 1 ton of moist material. The mixing is provided by a number of screw augers i.e., designed to lift the substrate as they turn that are mounted on a carriage on top of the bioreactor Fig. 10.3 . This carriage...
Stirred Beds with Mechanical Agitators
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....
Main Ideas Underlying Process Control
In this chapter we present the basics that the non-engineer needs to know about process control in order to understand the discussion of the application of process control to solid-state fermentation SSF bioreactors that will be presented in Chap. 28. Here, the idea of feedback will be introduced as well as the main components of a control loop. In addition, the most used control algorithms in the process industries will be described and some hints on how to simplify their application will be...
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....
Further Reading Tts
Selected examples from the SSF literature in which models are developed that describe the various heat and mass transfer phenomena described in this chapter. These models therefore contain terms similar to those shown in this chapter Mitchell DA, von Meien OF 2000 Mathematical modeling as a tool to investigate the design and operation of the Zymotis packed-bed bioreactor for solid-state fermentation. Biotechnol Bioeng 68 127-135 Mitchell DA, Tongta A, Stuart DM, Krieger N 2002 The potential for...
Further Reading Idq
A survey of kinetic profiles in SSF systems Viccini G, Mitchell DA, Boit SD, Gern JC, da Rosa AS, Costa RM, Dalsenter FDH, von Meien OF, Krieger N 2001 Analysis of growth kinetic profiles in solid-state fermentation. Food Technol Biotechnol 39 271-294 Use of response surface analysis for determining the optimum medium and conditions for growth and product formation Kalil SJ, Maugeri F, Rodrigues MI 2000 Response surface analysis and simulation as a tool for bioprocess design and optimization....
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...
Reduction of Upstream and Downstream Investment
In the batch mode of operation, a quantity of feed equal to the bioreactor capacity must be ready for loading at the start of each cycle. Chemical changes cannot be prevented when moist solid substrates are stored for long times, and there is always the danger of the growth of contaminants, so it is not feasible to prepare and cook the substrate gradually. Neither is it feasible to inoculate the substrate gradually if the bioreactor is to be operated in batch mode. Hence, the upstream equipment...
The Need for a Qualitative Understanding of SSF
As argued in Chap. 1, mathematical models of bioreactor operation will be important tools in the development of bioreactors for solid-state fermentation SSF processes. These mathematical models must describe quantitatively the various phenomena within the SSF process that can potentially limit the performance of the bioreactor. One of the key early steps in modeling is to identify what these phenomena are, and to unite them in a qualitative description of the system, at an appropriate level of...
What Are the Current and Potential Applications of SSF
The considerations raised in the previous section have meant that SSF technology has been used for many centuries. Some examples of traditional SSF processes are tempe, which involves the cultivation of the fungus Rhizopus oligosporus on cooked soybeans. The fungal mycelium binds the soybeans into a compact cake, which is then fried and eaten as a meat substitute. This fermented food is quite popular in Indonesia the koji step of soy sauce manufacture, which involves the cultivation of the...
The General Steps of an SSF Process
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...
BlowerCompressor Selection and Flow Rate Control
The air blower is likely to be responsible for a large proportion of the energy consumed in bioreactor operation and therefore selection of an appropriate blower is very important. In general, SSF bioreactors need high air flow-rates at low pressures. If the pressure drop of the whole system, including piping, accessories, and bioreactor, is equal to or less than 35 cm of water, a fan is the best device. The power consumed by a fan P, kW can be calculated as follows where F is the air flow-rate...
Info Jpp
a The program converts all input variables and parameters to a consistent set of units. Note that where biomass is mentioned within the units, this represents dry biomass. b When the outlet gas water activity falls below this value, a mixing event is triggered during which water is added to the bed. c The inlet air temperature is also used as the initial temperature of the gas phase within the bed Tgo C . d Used to calculate the initial water content of the solids Wo, kg-water kg-dry-solids-1 ,...
Cataract Flow In Drum Coater
where NC is in rpm and D is the drum diameter in meters. For both a static drum 0 rpm and a drum rotating at the critical speed, there is no mixing action within the bed. For the slipping and slumping flow regimes, which occur when the rotational rate is less than 10 of the critical rotational speed, the bed moves essentially as a whole, meaning that the amount of mixing within the bed itself is negligible. As the rotational speed increases through moderate rotational rates from 10 to 60 of the...