The Interaction Mechanism between Microorganisms and Substrate in the Biodegradation of Polycaprolactone CARINE LEFE ` VRE, 1 ADAMS TIDJANI, 2 CORINNE VANDER WAUVEN, 3 CHRISTIANE DAVID 1 1 Universite ´ Libre de Bruxelles, Chimie des Polyme `res et des Syste `mes Organise ´s, Campus Plaine, 206/1, Boulevard du Triomphe, 1050 Brussels, Belgium 2 Laboratoire des D.S.T.N., Faculte ´ des Sciences, Universite ´ Cheikh Anta Diop de Dakar; Dakar-Fann, Se ´ne ´gal 3 Institut de Recherches Microbiologiques JM Wiame, Avenue E. Gryson, 1, 1070 Brussels, Belgium Received 21 December 2000; accepted 16 May 2001 Published online 5 December 2001 ABSTRACT: The present work concerns the interplay of the degradation mechanism and the nature of the interaction between microorganisms and substrate. The biodegrada- tion of polycaprolactone films by a pure strain of microorganisms isolated from an industrial composting unit for household refuse was studied in minimal medium with the polymer as sole carbon source. In conditions where the polymer surface is colonized and a biofilm is formed (under a low stirring rate), polymer weight loss is limited, whereas total degradation is observed when stirring conditions prevent biofilm forma- tion. In the first case, holes are observed in the degraded film and a polysaccharide responsible for microorganism adhesion was identified by FTIR. SEM observation of the polymer surface as a function of the degradation time suggests that the crystalline and amorphous phase are degraded at about the same rate in the first case, whereas the amorphous phase is preferentially degraded in the latter. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 83: 1334 –1340, 2002 Key words: biodegradation; polycaprolactone; biofilm; FTIR; SEM INTRODUCTION To reduce the proportion of plastics in solid waste, biodegradable plastics were developed for specific applications. Polycaprolactone is well known for its biodegradability; it is produced industrially in blends with starch. 1 The biodegradability of poly- caprolactone was observed in the presence of mi- croorganisms in many environments. The main drawbacks of the exposure methods which were developed (landfill and compost simulations, soil burial, etc.) are their highly variable compositions in terms of both chemistry and microbial popula- tions. 2 Several parameters, such as polymer mo- lecular weight, crystalline morphology, film thick- ness, and degradation conditions, influence polyca- prolactone biodegradation. 3–9 In our laboratory, we have undertaken the study of the degradation mechanism, working with a pure strain of microor- ganism from an industrial compost for household refuse selected for its ability to degrade polycap- rolactone. This strain is able to grow in a minimal medium with polycaprolactone as the sole source of carbon. Depending on the stirring method and velocity, growth results in the formation of either a cell suspension in the medium or a biofilm at the surface of the polymer. The attached cells and Correspondence to: C. Davis (christiane.david@village. uunet.be). Journal of Applied Polymer Science, Vol. 83, 1334 –1340 (2002) © 2002 John Wiley & Sons, Inc. DOI 10.1002/app.10124 1334