BIODEGRADABLE POLYMERS R. CHANDRA, RENU RUSTGI Department of Polymer Technology and Applied Chemistry, Delhi College of Engineering, Delhi-110006, India 1273 Pergamon Prog. Polym. Sci., Vol. 23, 1273–1335, 1998 Copyright  1998 Elsevier Science Ltd Printed in Great Britain. All rights reserved. 0079–6700/98 $ - see front matter S0079–6700(97)00039–7 CONTENTS 1. General introduction 1274 2. Natural biodegradable polymers 1275 2.1. Polysaccharides 1275 2.1.1. Starch 1276 2.1.2. Cellulose 1279 2.1.3. Chitin and chitosan 1282 2.1.4. Alginic acid 1282 2.2. Polypeptides of natural origin 1282 2.2.1. Gelatin 1282 2.3. Bacterial polyesters 1283 3. Polymer with hydrolyzable backbones 1284 3.1. Polyesters 1286 3.2. Polycaprolactone 1286 3.3. Polyamides 1286 3.4. Polyurethanes and polyureas 1287 3.5. Polyanhydrides 1287 3.6. Poly(amide-enamine)s 1287 4. Polymers with carbon backbones 1288 4.1. Poly(vinyl alcohol) and poly(vinyl acetate) 1288 4.2. Polyacrylates 1289 5. Factors affecting biodegradation 1289 5.1. Effect of polymer structure 1289 5.2. Effect of polymer morphology 1290 5.3. Effects of radiation and chemical treatments 1291 5.4. Effect of molecular weight 1292 6. Mode of biodegradation 1293 6.1. Microorganisms 1292 6.1.1. Fungi 1292 6.1.2. Bacteria 1294 6.2. Enzymes 1294 6.2.1. Physical factors affecting the activity of enzymes 1295 6.2.2. Enzyme mechanisms 1295 6.2.2.1. Biological oxidation 1295 6.2.2.2. Biological hydrolysis 1296