Chronological Development Of Fermentation Industry

1. AN INTRODUCTION TO FERMENTATION PROCESSES 1

The range of fermentation processes 1

Microbial biomass 1

Microbial enzymes 2

Microbial metabolites 3

Recombinant products 4

Transformation processes 5

The chronological development of the fermentation industry 5

The component parts of a fermentation process 9 References

2. MICROBIAL GROWTH KINETICS 13

Batch culture 13

Continuous culture 16

Multistage systems 19

Feedback systems 19

Internal feedback 19

External feedback 20

Comparison of batch and continuous culture in industrial processes 21

Biomass productivity 21

Metabolite productivity 22

Continuous brewing 24

Continuous culture and biomass production 25

Comparison of batch and continuous culture as investigative tools 26

Fed-batch culture 27

Variable volume fed-batch culture 27

Fixed volume fed-batch culture 28

Cyclic fed-batch culture 29

Application of fed-batch culture 29

Examples of the use of fed-batch culture 30

References 31

3. THE ISOLATION, PRESERVATION AND IMPROVEMENT OF INDUSTRIALLY

IMPORTANT MICRO-ORGANISMS 35

The isolation of industrially important micro-organisms 35

Isolation methods utilizing selection of the desired characteristic 37

Enrichment liquid culture 37

Enrichment cultures using solidified media 39

Isolation methods not utilizing selection of the desired characteristic 39

Screening methods 40

The preservation of industrially important micro-organisms 42

Storage at reduced temperature 42

Storage on agar slopes 42

Storage under liquid nitrogen 42

Storage in a dehydrated form 42

Dried cultures 42

Lyophilization 42

Quality control of preserved stock cultures 43

The improvement of industrial micro-organisms 43

The selection of induced mutants synthesizing improved levels of primary metabolites 45

Modification of the permeability 47

The isolation of mutants which do not produce feedback inhibitors or repressors 48

Examples of the use of auxotrophs for the production of primary metabolites 50

The isolation of mutants that do not recognize the presence of inhibitors and repressors 53 The isolation of induced mutants producing improved yields of secondary metabolites where directed selection is difficult to apply 57

The isolation of auxotrophic mutants 61

The isolation of resistant mutants 62 Mutants resistant to the analogues of primary metabolic precursors of the secondary metabolite 63

Mutants resistant to the feedback effects of the secondary metabolite 63 The isolation of mutants resistant to the toxic effects of the secondary metabolite in the trophophase 64 The isolation of mutants in which secondary metabolite synthesis gives resistance to toxic compounds 64

The isolation of revertant mutants 65 The isolation of revertants of mutants auxotrophic for primary metabolites which may influence the production of a secondary metabolite 65 The isolation of revertants of mutants which have lost the ability to produce the secondary metabolite 65

The use of recombination systems for the improvement of industrial micro-organisms 66

The application of the parasexual cycle 66

The application of protoplast fusion techniques 68

The application of recombinant DNA techniques 70

The production of heterologous proteins 71 The use of recombinant DNA technology for the improvement of native microbial products 73 The improvement of industrial strains by modifying properties other than the yield of product 79

The selection of stable strains 79

The selection of strains resistant to infection 80

The selection of non-foaming strains 80

The selection of strains which are resistant to components in the medium 81

The selection of morphologically favourable strains 81

The selection of strains which are tolerant of low oxygen tension 82

The elimination of undesirable products from a production strain 82

The development of strains producing new fermentation products 82

Summary 85

References 85

4. MEDIA FOR INDUSTRIAL FERMENTATIONS 93

Introduction 93

Typical media 94

Medium formulation 94

Water 97

Energy sources 97

Carbon sources 97

Factors influencing the choice of carbon source 97

Examples of commonly used carbon sources 99

Carbohydrates 99

Oils and fats 99

Hydrocarbons and their derivatives 100

Nitrogen sources 101

Examples of commonly used nitrogen sources 101

Factors influencing the choice of nitrogen source 101

Minerals 102

Chelators 104

Growth factors 104

Nutrient recycle 105

Buffers 105

The addition of precursors and metabolic regulators to media 105

Precursors 105

Inhibitors 105

Inducers 106

Oxygen requirements 108

Fast metabolism 108

Rheology 108

Antifoams 109

Medium optimization 110

Animal cell media 115

Serum 115

Serum-free media supplements 115

Protein-free media 116

Trace elements 116

Osmolality 116

pH 116

Non-nutritional media supplements 116

References 116

5. STERILIZATION 123

Introduction 123

Medium sterilization 123

The design of batch sterilization processes 129

Calculation of the Del factor during heating and cooling 129

Calculation of the holding time at constant temperature 130

Richards' rapid method for the design of sterilization cycles 130

The scale up of batch sterilization processes 130

Methods of batch sterilization 131

The design of continuous sterilization processes 132

Sterilization of the fermenter 137

Sterilization of the feeds 137

Sterilization of liquid wastes 137

Filter sterilization 137

Filter sterilization of fermentation media 139

Filter sterilization of air 140

Sterilization of fermenter exhaust air 140

The theory of depth filters 140

The design of depth filters 144

References 145

6. THE DEVELOPMENT OF INOCULA FOR INDUSTRIAL FERMENTATIONS 147

Introduction 147

Criteria for the transfer of inoculum 149

The development of inocula for yeast processes 151

Brewing 151

Bakers' yeast 153

The development of inocula for bacterial processes 153

The development of inocula for mycelial processes 155

Sporulation on solidified media 155

Sporulation on solid media 155

Sporulation in submerged culture 156

The use of the spore inoculum 158

Inoculum development for vegetative fungi 160 The effect of the inoculum on the morphology of filamentous organisms in submerged culture 160

The aseptic inoculation of plant fermenters 162

Inoculation from a laboratory fermenter or a spore suspension vessel 162

Inoculation from a plant fermenter 163

References 164

7. DESIGN OF A FERMENTER 167

Introduction j

Basic functions of a fermenter for microbial or animal cell culture 168

Aseptic operation and containment 169

Overall containment categorization 172

Body construction 172

Construction materials 172

Temperature control 176

Aeration and agitation 17g

The agitator (impeller) 178

Stirrer glands and bearings 181

The stuffing box (packed-gland seal) 181

The mechanical seal 181

Magnetic drives 182

Baffles 183

The aeration system (sparger) 183

Porous sparger 183

Orifice sparger 184

Nozzle sparger 185

Combined sparger-agitator 185

The achievement and maintenance of aseptic conditions 185

Sterilization of the fermenter 186

Sterilization of the air supply 186

Sterilization of the exhaust gas from a fermenter 187

The addition of inoculum, nutrients and other supplements 187

Sampling 187

Feed ports 189

Sensor probes 189

Foam control 190

Monitoring and control of various parameters 192

Valves and steam traps 192

Gate valves 192

Globe valves 192

Piston valves 193

Needle valves 193

Plug valves 194

Ball valves 194

Butterfly valves 194

Pinch valves 194

Diaphragm valves 194

The most suitable valve 195

Check valves 196

Pressure-control valves 196

Pressure-reduction valves 196

Pressure-retaining valves 196

Safety valves 196

Steam traps 197

Complete loss of contents from a fermenter 198

Testing new fermenters 198

Other fermentation vessels 199

The Waldhof-type fermenter 199

Acetators and cavitators 199

The tower fermenter 200

Cylindro-conical vessels 201

Air-lift fermenters 202

The deep-jet fermenter 204

The cyclone column 205

The packed tower 205

Rotating-disc fermenters 206

Animal cell culture Stirred fermenters Air-lift fermenters Microcarriers Encapsulation Hollow fibre chambers Packed glass bead reactors Perfusion cultures References

INSTRUMENTATION AND CONTROL Introduction

Methods of measuring process variables Temperature Mercury-in-glass thermometers Electrical resistance thermometers Thermistors Temperature control Flow measurement and control Gases Liquids Pressure measurement Pressure control Safety valves Agitator shaft power Rate of stirring

Redox

Carbon dioxide electrodes On-line analysis of other chemical factors

Enzyme and microbial electrodes Near infra-red spectroscopy Mass spectrometers Control systems Manual control Automatic control

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