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Proportional control

Integral control 231

Derivative control

Combinations of methods of control 232

Proportional plus integral control 232

Proportional plus derivative control 232

Proportional plus integral plus derivative control 232

Controllers 232

More complex control systems 232

Computer applications in fermentation technology 234

Components of a computer-linked system 234

Data logging 236

Data analysis 236

Process control 237

References 239

9. AERATION AND AGITATION 243

Introduction 243

The oxygen requirements of industrial fermentations 243

Oxygen supply 246

Determination of KLa values 247

The sulphite oxidation technique 248

Gassing-out techniques 248

The static method of gassing out 248

The dynamic method of gassing out 249

The oxygen-balance technique 251

Fluid rheology 252

Bingham plastic rheology 253

Pseudoplastic rheology 253

Dilatant rheology 254

Casson body rheology 254

Factors affecting KLa values in fermentation vessels 254

The effect of air-flow rate on KLa 254

Mechanically agitated reactors 254

Non-mechanically agitated reactors 256

Bubble columns 256

Air-lift reactors 256

The effect of the degree of agitation on KLa 257

The relationship between KLa and power consumption 257

The relationship between power consumption and operating variables 258

The effect of medium and culture rheology on KLa 260

Medium rheology 260

The effect of microbial biomass on KLa 261

Agitator design for non-Newtonian fermentations 261

The manipulation of mycelial morphology 264

The effect of microbial products on aeration 266

The effect of foam and antifoams on oxygen transfer 267

The balance between oxygen supply and demand 267

Controlling biomass concentration 268

Controlling the specific oxygen uptake rate 269

Scale-up and scale-down 269

Scale-up of aeration/agitation regimes in stirred tank reactors 270

The scale-up of air-lift reactors 272

Scale-down methods 272

References 272

10. THE RECOVERY AND PURIFICATION OF FERMENTATION PRODUCTS 277

Introduction 277

Removal of microbial cells and other solid matter 280

Foam separation 280

Precipitation 280

Filtration 281

Theory of filtration 281

The use of filter aids 282

Batch filters 283

Plate and frame filters 283

Pressure leaf filters 283

Vertical metal-leaf filter 283

Horizontal metal-leaf filter 283

Stacked-disc filter 283

Continuous filters 284

Rotary vacuum filters 284

String discharge 284

Scraper discharge 285

Scraper discharge with precoating of the drum 285

Cross-flow filtration (tangential filtration) 285

Centrifugation 287

Cell aggregation and flocculation 287

The range of centrifuges 288

The basket centrifuge (perforated-bowl basket centrifuge) 288

The tubular-bowl centrifuge 288

The solid-bowl scroll centrifuge (decanter centrifuge) 289

The multichamber centrifuge 289

The disc-bowl centrifuge 290

Cell disruption 292

Physical-mechanical methods 292

Liquid shear 292

Solid shear 293

Agitation with abrasives 293

Freezing-thawing 293

Ultrasonication 294

Chemical methods 294

Detergents 294

Osmotic shock 295

Alkali treatment 295

Enzyme treatment 295

Liquid-liquid extraction 296

Solvent recovery 299

Two-phase aqueous extraction 300

Supercritical fluid extraction 301

Chromatography 301

Adsorption chromatography 302

Ion exchange 302

Gel permeation 303

Affinity chromatography 303

Reverse phase chromatography (RPC) 303

High performance liquid chromatography (HPLC) 304

Continuous chromatography 304

Membrane processes 304

Ultrafiltration and reverse osmosis 304

Ultrafiltration 304

Reverse osmosis 305

Liquid membranes 305

Drying 305

Crystallization 307

Whole broth processing 307

References 308

EFFLUENT TREATMENT 313

Introduction 313

Dissolved oxygen concentration as an indicator of water quality 314

Site surveys 314

The strengths of fermentation effluents 315

Treatment and disposal of effluents 316

Disposal 317

Seas and rivers 317

Lagoons (oxidation ponds) 317

Spray irrigation 317

Well disposal 318

Landfilling 318

Incineration 318

Disposal of effluents to sewers 318

Treatment processes 318

Physical treatment 319

Chemical treatment 320

Biological treatment 320

Aerobic processes 320

Trickling filters 320

Towers 321

Biologically aerated filters (BAFs) 321

Rotating biological contactors (rotating disc contactors) 322

Rotating drums 322

Fluidized-bed systems 322

Activated sludge processes 322

Anaerobic treatment 324

Anaerobic digestion 324

Anaerobic digesters 325

Anaerobic filters 325

Up-flow anaerobic sludge blankets (UASB) 326

By-products 326

Distilleries 326

Breweries 327

Amino acid wastes 327

Fuel alcohol wastes 327

References 327

12. FERMENTATION ECONOMICS 331

Introduction 33 j

Isolation of micro-organisms of potential industrial interest 332

Strain improvement 333

Market potential 334 Some effects of legislation on production of antibiotics and recombinant proteins in the

Plant and equipment 336

Media 339

Air sterilization 340

Heating and cooling 340

Aeration and agitation 341

Batch-process cycle times 342

Continuous culture 343

Recovery costs 343

Water usage and recycling 344

Effluent treatment 345

References 346

Index 351

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