3
Biochemical Engineering Approach to SSF Bioreactors . . . . . . . 79
4
Microscale Phenomena Occurring Within SSF Bioreactors . . . . . 81
4.1 Microbial Growth in Response to its Environment . . . . . . . . . . 82
4.1.1 Effects of Nutrients, Oxygen, and Biomass Concentrations on Growth 82
4.1.2 Effect of Temperature on Growth . . . . . . . . . . . . . . . . . . . . 86
4.1.3 Effect of pH on Growth . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.1.4 Effect of Water Activity on Growth . . . . . . . . . . . . . . . . . . . 88
4.1.5 Combining Environmental Effects . . . . . . . . . . . . . . . . . . . 88
4.2 Microbial Growth Forms Within SSF Bioreactors . . . . . . . . . . . 89
4.3 Effect of Microbial Growth on the Environment . . . . . . . . . . . 91
4.4 Intraparticle Diffusion of Enzymes, Nutrients, Hydrolysis
Products, and Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.5 Destruction of the Particle Due to Growth . . . . . . . . . . . . . . 95
4.6 Potential to Develop a Microscale Model of Growth . . . . . . . . . 96
5
Bioreactor Design and Macroscale Phenomena Occurring
in Bioreactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.1 General Roles of a Bioreactor . . . . . . . . . . . . . . . . . . . . . . 97
5.1.1 Containing of the Substrate Bed . . . . . . . . . . . . . . . . . . . . 98
5.1.2 Containing of the Process Organism . . . . . . . . . . . . . . . . . . 98
5.1.3 Protecting the Process Organism Against Contamination . . . . . . 98
5.1.4 Controlling Environmental Conditions to Optimize Growth
and Product Formation . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.1.5 Maintenance of Homogeneity Within the Substrate Bed . . . . . . . 99
5.1.6 Facilitating Other Aspects of Processing . . . . . . . . . . . . . . . . 99
5.1.7 Mode of Bioreactor Operation . . . . . . . . . . . . . . . . . . . . . 100
5.1.8 Key Considerations in Choosing a Bioreactor for a Particular Process 101
5.2 Unmixed Beds and the Absence of Forced Aeration – Trays . . . . . 103
5.3 Unmixed Beds with Forced Aeration Through the Bed –
Packed Beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.4 Mixed Beds Without Forced Aeration – Rotating Drums,
Stirred Drums, and Screw Bioreactors . . . . . . . . . . . . . . . . . 110
5.5 Mixed Beds with Forced Aeration – Gas-Solid Fluidized Beds,
Stirred Drums, and the Rocking Drum . . . . . . . . . . . . . . . . 112
5.5.1 Gas Solid-Fluidized Beds . . . . . . . . . . . . . . . . . . . . . . . . 112
5.5.2 Stirred Aerated Beds . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
5.5.3 Rocking Drum Bioreactor . . . . . . . . . . . . . . . . . . . . . . . . 116
5.5.4 Evaluation of Mixed Aerated Bioreactors . . . . . . . . . . . . . . . 117
6
Approaches to Scale-Up of SSF Bioreactors . . . . . . . . . . . . . . 117
7
Measurement and Control Within SSF Bioreactors . . . . . . . . . . 120
7.1 Application of Advanced Control Techniques . . . . . . . . . . . . . 121
7.2 Application of Off-Line Measurement Techniques . . . . . . . . . . 122
7.2.1 Measuring Water Content and Water Activity . . . . . . . . . . . . . 122
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Biochemical Engineering Approach to SSF Bioreactors . . . . . . . 79
4
Microscale Phenomena Occurring Within SSF Bioreactors . . . . . 81
4.1 Microbial Growth in Response to its Environment . . . . . . . . . . 82
4.1.1 Effects of Nutrients, Oxygen, and Biomass Concentrations on Growth 82
4.1.2 Effect of Temperature on Growth . . . . . . . . . . . . . . . . . . . . 86
4.1.3 Effect of pH on Growth . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.1.4 Effect of Water Activity on Growth . . . . . . . . . . . . . . . . . . . 88
4.1.5 Combining Environmental Effects . . . . . . . . . . . . . . . . . . . 88
4.2 Microbial Growth Forms Within SSF Bioreactors . . . . . . . . . . . 89
4.3 Effect of Microbial Growth on the Environment . . . . . . . . . . . 91
4.4 Intraparticle Diffusion of Enzymes, Nutrients, Hydrolysis
Products, and Oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.5 Destruction of the Particle Due to Growth . . . . . . . . . . . . . . 95
4.6 Potential to Develop a Microscale Model of Growth . . . . . . . . . 96
5
Bioreactor Design and Macroscale Phenomena Occurring
in Bioreactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.1 General Roles of a Bioreactor . . . . . . . . . . . . . . . . . . . . . . 97
5.1.1 Containing of the Substrate Bed . . . . . . . . . . . . . . . . . . . . 98
5.1.2 Containing of the Process Organism . . . . . . . . . . . . . . . . . . 98
5.1.3 Protecting the Process Organism Against Contamination . . . . . . 98
5.1.4 Controlling Environmental Conditions to Optimize Growth
and Product Formation . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.1.5 Maintenance of Homogeneity Within the Substrate Bed . . . . . . . 99
5.1.6 Facilitating Other Aspects of Processing . . . . . . . . . . . . . . . . 99
5.1.7 Mode of Bioreactor Operation . . . . . . . . . . . . . . . . . . . . . 100
5.1.8 Key Considerations in Choosing a Bioreactor for a Particular Process 101
5.2 Unmixed Beds and the Absence of Forced Aeration – Trays . . . . . 103
5.3 Unmixed Beds with Forced Aeration Through the Bed –
Packed Beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.4 Mixed Beds Without Forced Aeration – Rotating Drums,
Stirred Drums, and Screw Bioreactors . . . . . . . . . . . . . . . . . 110
5.5 Mixed Beds with Forced Aeration – Gas-Solid Fluidized Beds,
Stirred Drums, and the Rocking Drum . . . . . . . . . . . . . . . . 112
5.5.1 Gas Solid-Fluidized Beds . . . . . . . . . . . . . . . . . . . . . . . . 112
5.5.2 Stirred Aerated Beds . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
5.5.3 Rocking Drum Bioreactor . . . . . . . . . . . . . . . . . . . . . . . . 116
5.5.4 Evaluation of Mixed Aerated Bioreactors . . . . . . . . . . . . . . . 117
6
Approaches to Scale-Up of SSF Bioreactors . . . . . . . . . . . . . . 117
7
Measurement and Control Within SSF Bioreactors . . . . . . . . . . 120
7.1 Application of Advanced Control Techniques . . . . . . . . . . . . . 121
7.2 Application of Off-Line Measurement Techniques . . . . . . . . . . 122
7.2.1 Measuring Water Content and Water Activity . . . . . . . . . . . . . 122
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