Bioresource Technology

Tanveer Bilal Pirzadah, is Assistant Professor at the University Centre for Research and Development at Chandigarh University in Punjab, India. Bisma Malik, is Assistant Professor at the University Centre for Research and Development at Chandigarh University in Punjab, India. Rouf Ahmad Bhat, works in the Department of School Education, Government of Jammu and Kashmir, India Khalid Rehman Hakeem, is Professor at King Abdulaziz University in Jeddah, Saudi Arabia.

Part I: The Application of Bioresource Technology in the Functional Food Sector 1

1 Millets: Robust Entrants to Functional Food Sector 3
Sagar Maitra, Sandipan Pine, Pradipta Banerjee, Biswajit Pramanick and Tanmoy Shankar

1.1 Introduction 4

1.2 Nomenclature and Use 5

1.3 Description of Important Millets 7

1.3.1 Sorghum 7

1.3.2 Pearl Millet 7

1.3.3 Finger Millet 8

1.3.4 Foxtail Millet 8

1.3.5 Proso Millet 8

1.3.6 Barnyard Millet 8

1.3.7 Little Millet 9

1.3.8 Kodo Millet 9

1.3.9 Brown-Top Millet 9

1.4 Millets: The Ancient Crops 9

1.5 Current Scenario of Millets Production 10

1.6 Nutritional Importance of Millets 11

1.6.1 Millets as Functional Food 13

1.6.2 Anti-Oxidant and Anti-Aging Properties 14

1.6.3 Protection Against Cancer 15

1.6.4 Anti-Diabetic Properties 15

1.6.5 Protection Against Gastro-Intestinal Disorders 15

1.6.7 Protection Against Osteoporosis 16

1.7 Changes in Food Consumption Pattern and Future Demand 16

1.8 Food and Nutritional Security 17

1.9 Climate Change and Associated Threat to Agriculture 18

1.10 Millets: As Climate Smart Crops 19

1.11 Future Agriculture: Smart Technologies in Millet Farming 20

1.12 Conclusions 21

References 21

2 The Art and Science of Growing Microgreens 28
Sreenivasan Ettammal

2.1 Introduction 28

2.2 Historical Background 29

2.3 Health Benefits of Microgreens 29

2.3.1 Source of Functional Food Components 29

2.3.2 Component of Space Life Support Systems 30

2.3.3 Component of Nutritional Diet of Troops and Residents of High Altitude Regions 30

2.4 Cultivation Practices 30

2.4.1 Species Selection 30

2.4.2 Growing Media and Propagation Felts 30

2.4.3 Growing Process 31

2.5 Quality and Shelf Life 33

2.6 Market Trends 34

2.7 Future Outlook 34

2.8 Conclusions 34

References 35

3 Novel Nutraceuticals From Marine Resources 38
Zadia Qamar, Amna Syeda, Javed Ahmed and M. Irfan Qureshi

3.1 Introduction 38

3.2 Marine Microorganisms as a Source of Nutraceuticals 39

3.2.1 Marine Algae 40

3.2.2 Marine Invertebrates 41

3.2.2.1 Sponges 41

3.2.2.2 Crustaceans, Echinoderms and Molluscs 42

3.2.2.3 Marine Fishes 42

3.2.2.4 Marine Actinomycetes 43

3.2.2.5 Marine Fungi 43

3.2.2.6 Marine Bacteria 44

3.3 Classification of Different Nutraceuticals Obtained from Marine Environment 44

3.3.1 Polysaccharides 44

3.3.2 Marine Lipids 45

3.3.3 Natural Pigments from Marine Sources 45

3.3.4 Chitosan and Its Derivatives 48

3.3.5 Proteins and Peptides 48

3.3.6 Minerals, Vitamins and Enzymes 49

3.3.7 Marine Probiotics and Phenolic Compounds 49

3.4 Important Bioactive Metabolites and Their Biological Properties 50

3.5 Current Status of Nutraceuticals in Market 50

3.6 Conclusion and Future Recommendations 51

References 51

4 Bioprospecting of Bioresources: Creating Value From Bioresources 57
Deepika Kathuria and Sumit S. Chourasiya

4.1 Introduction 57

4.2 Bioprospecting in Various Industrial Fields 59

4.2.1 Pharmaceutical Industries 59

4.2.1.1 Drugs From Plants 59

4.2.1.2 Drugs From Bugs 61

4.2.1.2.1 Microbes 61

4.2.1.2.2 Enzymes 61

4.2.1.3 Drugs From Aquatics 69

4.3 Chemical Industries 70

4.3.1 Biocatalysis 70

4.4 Bioprospecting in Agriculture 73

4.4.1 Biofertilizers and Biopesticides 73

4.4.2 Bioremediation 74

4.5 Bioprospecting in Beautification/Cosmetics 74

4.6 Bioprospecting in Detergent Industry 78

4.7 Bioprospecting in Textile Industry 80

4.8 Bioprospecting in Paper Industry 81

4.9 Bioprospecting in Food Industry 82

4.9.1 Bioprospecting in Brewing Industry 83

4.10 Diagnostic 83

4.10.1 Application of Enzymes for the Detection of Pyrogens in PharmaceuticalProducts 84

4.10.2 Bioprospecting in Biofuel Production 84

4.11 Conclusions and Future Perspectives 84

References 85

5 Green and Smart Packaging of Food 93
Gülden Gökşen, Derya Boyacı and Nick Tucker

5.1 Introduction 93

5.2 Green Packaging in Food 95

5.3 Properties of Green Packaging Materials 95

5.4 Mechanical Properties of Green Packaging Materials 97

5.5 Barrier Properties of Green Packaging 98

5.6 Green Packaging Materials with Active Properties 99

5.7 Biodegradation Mechanisms of Green Packaging 101

5.8 Main Green Food Packaging 104

5.8.1 Poly(lactic Acid) (PLA) 104

5.8.2 Polyhydroxyalkaonate (PHA) 105

5.8.3 Starch-based Materials 106

5.8.4 Cellulose-based Materials 106

5.9 Life Cycle of Green Packaging Materials 107

5.10 Smart Packaging in Food 108

5.11 Indicators for Smart Packaging 110

5.11.1 Time-Temperature Indicator (TTI) 110

5.11.2 Freshness Indicators 111

5.11.3 Packaging Integrity Indicators 112

5.12 Sensor Applications for Smart Packaging 113

5.13 Data Carriers for Smart Packaging 119

5.14 Regulatory Aspects 121

5.15 Conclusion and Future Perspectives 122

References 123

6 Nanosensors: Diagnostic Tools in the Food Industry 133
Stephen Rathinaraj Benjamin, Eli José Miranda Ribeiro Junior, Vennilavan Thirumavalavan and Antony De Paula Barbosa

6.1 Introduction 133

6.2 Identification of Foodborne Pathogens and Toxins 134

6.3 Pesticides and Carcinogenic Detection 140

6.3.1 Nitrites-Carcinogenic Detection 141

6.3.2 Mycotoxin Detection 141

6.3.3 Food Packaging 142

6.3.4 Food Freshness Detection 143

6.4 Chemicals and Food Additives Detection 144

6.4.1 Preservatives 144

6.4.2 Dyes 144

6.4.3 Sweeteners 145

6.4.4 Antioxidants 145

6.4.5 Food Allergens 145

6.5 Nano-based Sensors for Smart Packaging 146

6.5.1 Nanobarcodes 147

6.5.2 e-NOSE and e-TONGUE 147

6.5.3 Oxygen Sensors 147

6.5.4 Humidity Sensors 148

6.5.5 Carbon Dioxide (CO2) Sensor 148

6.6 Challenges 149

6.7 Conclusions and Future Perspectives 150

References 150

7 Harnessing Genetic Diversity for Addressing Wheat-based Time Bound Food Security Projections: A Selective Comprehensive Practical Overview 160
Abdul Mujeeb-Kazi, Niaz Ali, Ian Dundas, Philip Larkin, Alexey Morghonov, Richard R-C Wang, Francis Ogbonnaya, Hanif Khan, Nasir Saeed, Shabir Wani, Mohammad Sohail Saddiq, Mohammad Jamil, Abdul Aziz Napar, Fatima Khalid, Mahjabeen Tariq, Rumana Keyani, Zeeshan Ali and Sanjaya Rajaram

7.1 The Global Wheat Scenario 162

7.2 Food Security: The Challenge of Feeding Over 9 Billion by 2050 163

7.3 Conventional Wheat Improvement Strategies 165

7.3.1 Breeding Methods 165

7.3.2 Recombination Breeding 166

7.3.3 Pedigree or Line Breeding 167

7.3.4 Bulk Method 168

7.3.5 Single Seed Descent (SSD) Method 168

7.3.6 Backcross Breeding 169

7.3.7 Modified Pedigree Bulk 169

7.3.8 Selected Bulk 170

7.3.9 Multiline Breeding 170

7.3.10 Shuttle Breeding 171

7.3.11 Doubled Haploid 172

7.3.12 Mutation Breeding 173

7.3.13 Hybrid Wheat 175

7.3.14 The XYZ System 176

7.4 Innovative Technologies for Accessing Novel Genetic Diversity 177

7.5 Major Global Locations of Wheat Genetic Diversity 179

7.6 Utilization of Genetic Diversity 179

7.6.1 Wide Crosses: The Historical Build-up 183

7.7 Distribution of Genetic Diversity: Gene Pools, Their Potential Impact and Research Integration for Practicality 185

7.7.1 The Gene Pool Structure 186

7.7.1.1 Primary Gene Pool Species 186

7.7.1.2 The A Genome (Triticum Boeoticum, T. Monococcum, T. Urartu; 2n = 2x = 14, AA) 187

7.7.1.3 The D Genome (Aegilops Tauschii = Goat Grass; 2n = 2x = 14, DD) 187

7.7.1.4 Secondary Gene Pool Species 188

7.7.1.5 Selected Secondary Gene Pool Species Utilization Example 188

7.7.1.6 Tertiary Gene Pool Species 188

7.7.1.7 The Gene Pool Potential Recap 189

7.7.1.8 Conclusion: Transfer Prerequisites Across Gene Pools 191

7.8 Underexplored Areas 191

7.8.1 Land Races: Definitions, General Characteristics and Practicality Potential 191

7.8.2 Wheat Landraces: An Additive Diversity Source 193

7.8.3 Important Collections of Wheat Landraces 194

7.9 Perennial Wheat 198

7.9.1 The Concept of a More Sustainable Perennial Wheat-Like Cereal. Is It Feasible? 198

7.9.1.1 What Benefit/s Would Come? 198

7.9.1.2 Potential Pitfalls 198

7.9.1.3 What Approaches Can Be Conceived? 199

7.9.1.4 What Progress? 200

7.9.1.5 What Lessons? 201

7.9.1.6 Suggested Way Forward?

7.9.2 Genetic Engineering for Wheat Improvement Focused on a Few Major Food Security Aspects 204

7.9.2.1 Tissue Culture and Transformation of Wheat 204

7.9.2.2 Production of Genetically-Modified Wheat 205

7.9.2.3 CRISPR/Cas9 Genome Editing in Wheat 205

7.9.2.4 Potential Traits for Genetic Improvement of Wheat Through Biotechnology 206

7.9.2.5 Yield Potential 206

7.9.2.6 Climate Change 207

7.9.2.7 Drought 207

7.9.2.8 Salinity 207

7.9.2.9 Heat 208

7.10 Historical Non-Conventional Trends for Exploiting Wheat’s Genetic Resources 208

7.10.1 Pre-1900 208

7.10.2 1901–1920 209

7.10.3 1921–1930 210

7.10.4 1931–1950 210

7.10.5 The Post-1950 Era: Preamble 211

7.10.6 Homoeologous Pairing 212

7.10.7 Isolation of Homoeologous Recombinants 213

7.10.8 Intergeneric Hybridization Steps for Wheat/Alien Crossing 214

7.10.8.1 Embryo Extraction and Handling 217

7.10.8.2 Pre-Breeding Protocol 218

7.10.8.3 Development of Genetic Stocks 219

7.10.8.4 Establishing a Living Herbarium 219

7.10.9 Interspecific Hybridization 219

7.10.10 Additive Durum Wheat Improvement 219

7.10.10.1 The Parental Choice 221

7.10.10.2 Shortening the Breeding Cycle by Inducing Homozygosity in Desired Early Breeding Generations 222

7.10.10.3 The Integration of Molecular Development Options for Efficiency and Precision 223

7.11 Alleviating Wheat Productivity Constraints via New Genetic Variation 224

7.11.1 Biotic Constraints 224

7.11.2 Insect Resistance 225

7.11.3 Root Diseases 226

7.11.4 Abiotic Stresses 226

7.11.5 Grain Yield 227

7.11.6 Bio-Fortification 228

7.11.7 Future Directions and Strategies 228

7.12 Accruing Potental Practical Benefits 230

7.13 Summary of the Practical Potential Benefits 236

7.14 The Role of Genomics Information Including Molecular Markers in Wheat 237

7.15 The Way Forward and Wrap-Up 248

7.16 Concerns 249

7.17 Conclusions 250

7.18 Some Perceptions 252

References 253

Part II: Bioresource and Future Energy Security 289

8 Waste-to-Energy: Potential of Biofuels Production from Sawdust as a Pathway to Sustainable Energy Development 291
Oyebanji Joseph Adewumi, Oyedepo Sunday Olayinka, Kilanko Oluwaseun and Dunmade Israel Sunday

8.1 Introduction 291

8.2 Overview of Potential WTE Technologies for Biomass Wastes 293

8.2.1 Thermo-Chemical Conversion Technologies 293

8.2.1.1 Gasification 294

8.2.1.2 Pyrolysis 294

8.2.1.3 Liquefaction 295

8.3 Biochemical Conversion Technologies 295

8.4 Potential Feedstocks for Waste-to-Energy 296

8.4.1 Agricultural Residues 296

8.4.2 Animal Waste 296

8.4.3 Forestry Residues 296

8.4.4 Industrial Wastes 296

8.4.5 Municipal Solid Waste (MSW) 297

8.4.6 Black Liquor 297

8.5 Waste-to-Energy and Sustainable Energy Development 297

8.6 Challenges and Future Prospects of Waste-to-Energy Technologies 298

8.7 Case Study: Application of Fast Pyrolysis for Conversion of Sawdust to Bio-Oil 299

8.7.1 Samples Collection and Experimental Analysis 299

8.7.2 Instrumentation and Experimental Set-up 299

8.7.3 GCMS Analysis 299

8.7.4 Chemical and Physical Composition of Biofuel Yield 300

8.7.5 Characterization of Bio-Oil Yield from Sawdust Samples 301

8.8 Economic and Environmental Benefits of Biofuel 304

8.8.1 Economics Benefits 304

8.8.2 Environmental Benefits of Biofuel 304

8.9 Conclusion and Recommendations 304

References 305

9 Biogas Production and Processing from Various Organic Wastes in Anaerobic Digesters and Landfills 310
Setareh Heidari, David A. Wood, Birendra K. Rajan and Ahmad Fauzi Ismail

9.1 Introduction 310

9.2 Urban Waste as a Raw Material for Biogas Production 311

9.2.1 Independent-Source Organic Waste 311

9.2.2 Sewage Sludge 312

9.3 Biogas Feedstock Properties 313

9.3.1 Suitability and Availability 313

9.3.2 Digestibility 318

9.3.3 Impurities with Digester-Disrupting Effects 318

9.3.4 Feedstocks Acting as AD Biogas Boosters 318

9.4 Biogas Production Technology Applied to Landfills 319

9.4.1 Anaerobic Digester Pre-Treatments 321

9.4.2 Digester Design and Process Optimization 322

9.4.3 Hydrolysis Enhancements 322

9.4.4 Bacterial Clean-up of AD Digester Effluent 323

9.4.5 Additives to Enhance Methane Yield 324

9.4.6 Biogas Upgrading Technologies 324

9.4.6.1 Carbon Dioxide Removal Technologies 324

9.4.7 Hydrogen Sulfide and Ammonia Removal 326

9.4.8 Siloxane Removal 326

9.5 Conclusions 326

References 327

10 Extremophiles as Gold Mines for Bioprospecting 332
Sheikh Tanveer Salam, Mukhtar Ahmad Malik and Tanveer Bilal Pirzadah

10.1 Introduction 332

10.2 Bioprospecting of Extremophiles 333

10.3 Bioprospecting of Thermophiles 338

10.4 Bioprospecting of Acidophiles 338

10.5 Bioprospecting of Psychrophiles 339

10.6 Bioprospecting of Halophiles 339

10.7 Bioprospecting of Metallophiles 339

10.8 Conclusion and Future Perspective 340

References 340

Part III: Bioresource Technology: Solution to Sustainable Environment and Management Policies 345

11 Algal-based Membrane Bioreactor for Wastewater Treatment 347
Setareh Heidari, David A. Wood and Ahmad Fauzi Ismail

11.1 Introduction 347

11.2 Algal Treatment System: Requirements and Complications 349

11.3 Elements of Microalgae Cultivation 350

11.4 Membranes and Their Application in Water and Wastewater Treatments 351

11.5 Algal Membrane Photobioreactors 353

11.6 Factors Affecting the Performance of Membrane Photobioreactors 356

11.6.1 Operating Factors 356

11.6.1.1 Temperature 356

11.6.2.2 Acidity-Alkalinity (Ph) 356

11.6.3.3 Flux and Permeate Flux Through the Reactors 356

11.6.4.4 Hydraulic and Solids Retention Time 356

11.6.5.5 Lighting 357

11.6.6.6 Aeration 357

11.7 Biomass Properties Impacting MPBR Performance 357

11.7.1 Microorganisms 357

11.7.2 Wastewater Properties 358

11.8 Challenges and Limitations 358

11.9 Future Directions for Algal-based Membrane Bioreactors

11.10 Conclusions 360

References 361

12 Engineering Plants for Metal Tolerance and Accumulation 373
Fernanda Maria Policarpo Tonelli, Flávia Cristina Policarpo Tonelli, Moline Severino Lemos, Helon Guimarães Cordeiro and Danilo Roberto Carvalho Ferreira

12.1 Introduction 373

12.2 Metals’ Bioremediation 374

12.2.1 Metal Phytoremediation 376

12.2.2 Non-Target Specific Engineered Plants to Metal Phytoremediation 377

12.2.3 Target Specific Genomic Engineering Technique to Enhance Plants Metal Tolerance and Accumulation 380

12.2.4 Important Methodologies to Engineer Plants to Metals Phytoremediation 383

12.3 Omics as Tools to Elucidate Important Genes to Plants Engineering 384

12.4 Conclusion 387

12.5 Future Perspectives 387

References 388

13 Recent Advances in Enzymatic Membranes and Their Sustainable Applications Across Industry 399
Setareh Heidari, David A. Wood and Ahmad Fauzi Ismail

13.1 Introduction 399

13.2 Enzymes 401

13.3 Global Demand for Commercial Enzymes 403

13.4 Membrane Technology 405

13.5 Fouling-Type Immobilization Membranes 407

13.6 Physical Procedures that Immobilize Enzyme in/on Membranes 407

13.7 Covalent Bonds that Immobilize Enzymes in/on Membranes 407

13.7.1 Amino Groups that Modify Membranes 408

13.7.2 Carboxylic Groups that Modify Membranes 408

13.7.3 Epoxy Groups that Modify Membranes 408

13.7.4 Azido Groups that Modify Membranes 409

13.8 Cross-linkage Procedures 409

13.9 Applications of Enzymatic Membrane Reactors 409

13.9.1 Treatment of Milk or Cheese Whey 409

13.9.2 Treatments of Animal, Plant, and Waste Oils and Fats 410

13.9.3 Pharmaceutical Production Employing Biocatalytic Membrane Reactors 410

13.9.4 Biocatalytic-Membrane Reactors for Biomedical Applications 411

13.9.5 Biocatalytic-Membrane Reactors for Agricultural Applications 411

13.9.6 Biocatalytic-Membrane Reactors for Waste-Water Treatment 411

13.10 Limitations, Challenges and Solution for EMR Applications 412

13.11 Conclusions 414

References 415

14 Use and Manufacture of Biopesticides and Biofertilizers in Latin America 424
Luis Jesús Castillo-Pérez, Juan José Maldonado Miranda and Candy Carranza-Álvarez

14.1 Introduction 424

14.2 Current Problems of Pesticides and Fertilizers in Latin America 425

14.3 Manufacture and Use of Biopesticides and Biofertilizers in Latin America 426

14.4 Manufacture of A Natural Repellent: A Case Study 430

14.5 Biotechnological Interventions in Biopesticide Synthesis 433

14.6 Biofertilizers Relevance and Plant Tolerance to Abiotic/Biotic Stress 433

14.7 Conclusions 436

References 436

15 Carbon Sequestration Alternatives for Mitigating the Accumulation of Greenhouse Gases in the Atmosphere 443
Erfan Sadatshojaei, Setareh Heidari, Zahra Edraki, David A. Wood and Ahmad Fauzi Ismail

15.1 Introduction 443

15.2 Impact of Greenhouse Gases 444

15.2.1 The Natural Greenhouse Impacts 444

15.2.2 Anthropogenic Greenhouse Impacts 445

15.3 Soil’s Role in the Sequestration of Carbon 446

15.3.1 Organic Carbon Sequestration 446

15.3.2 Inorganic Carbon Sequestration in Soils 449

15.4 Terrestrial Carbon Sequestration 450

15.4.1 Global Forest Management 450

15.4.1.1 Improving Agricultural Practices 452

15.4.1.2 Improving Biofuel Production Processes 453

15.5 Carbon Sequestration into Sub-Surface Geological Reservoirs 454

15.6 Oceanic Carbon Sequestration 456

15.7 Conclusions 457

References 458

16 Nanotechnology for Future Sustainable Plant Production Under Changing Environmental Conditions 466
Ayesha Tahir, Jun Kang, Jaffer Ali, Ameer Bibi and Shabbar Abbas

16.1 Introduction 466

16.2 Nanotechnology and Synthesis of Nanomaterials 467

16.2.1 Chemical Methods 467

16.2.2 Physical Methods 468

16.2.3 Biological Methods (Green Synthesis) 468

16.2.3.1 Plant Extract-based Synthesis of Nanomaterials 468

16.2.3.2 Microorganism-based Synthesis of Nanomaterials 469

16.3 Potential Applications of Nanotechnology in Agriculture for Climate Resilient Crops 470

16.3.1 Nanotechnology and Efficient Use of Input Resources 470

16.3.1.1 Water Use Efficiency Enhancement 470

16.3.1.2 Light Use Efficiency Enhancement 471

16.3.1.3 Nutrient Use Efficiency Enhancement 471

16.3.2 Nanomaterials and Plant Growth Enhancement 472

16.3.2.1 Germination and Vigor Enhancement 472

16.3.3 Nanoparticles to Mitigate Biotic Stresses 473

16.3.3.1 Nano-Pesticides 473

16.3.3.2 Nano-Fungicides 473

16.3.4 Nanomaterials to Mitigate Abiotic Stresses 474

16.3.4.1 Nanoparticles to Mitigate Drought Stress 474

16.3.4.2 Nanoparticles to Mitigate Metal Stress 474

16.3.4.3 Nanoparticles to Mitigate Salinity Stress 476

16.3.4.4 Nanoparticles to Mitigate Flooding Stress 477

16.3.4.5 Nanoparticles to Mitigate Heat Stress 477

16.3.4.6 Nanoparticles to Mitigate Cold Stress 477

16.4 Advances in Nanotechnology 478

16.4.1 Nanotechnology in Tissue Culture 478

16.4.2 NPs in Genome Editing 479

16.4.3 Nanosensors/Smart Plant Sensors 480

16.5 Conclusions and Future Prospects 481

References 482

17 Nanoscience: A Boon for Reviving Agriculture 493
Afrozah Hassan, Shabana Gulzar, Hanan Javid and Irshad Ahmad Nawchoo

17.1 Introduction 493

17.2 Agriculture: A Growing Need 494

17.2.1 Advanced Agriculture System Through Nanoscience 494

17.2.2 Nanofertilizers for Agriculture 495

17.3 Nano Herbicides and Agriculture 496

17.4 Nanotechnology Leading to Sustainable Agriculture 497

17.5 Conclusion 499

References 499

18 Profitability and Economics Analysis of Bioresource Management 504
Ghulam Mustafa

18.1 Introduction 504

18.2 Bioeconomy 504

18.3 Profitability Analysis of Bioresource-based Business 505

18.3.1 Short Rotation Cultivation (SRC) 506

18.3.2 Ecotourism 507

18.3.3 District Heating 507

18.3.4 Aquatic Biorefinery 508

18.4 Food Waste to Bioresource Businesses and Their Efficacies 509

18.4.1 Biofertilizer and Biogas Production 509

18.4.2 Biomethane 509

18.4.3 Bioethanol Fermentation 510

18.5 Bioresources for Risk Prevention and Poverty Alleviation 512

18.6 Conclusion 513

References 513

Index 517