The present work mainly dedicated to fungal degradation of poly(butylene adipate-co-terephthalate) [PBAT], to enclose the role of fungi in a real process of biodegradation, the degree of degradation, and to understand the kinetics of PBAT biodegradation. Respirometer tests were realized in soil at 30 °C, and in compost at 30 and 58 °C. Results have shown that temperature is one of the essential parameters governing the fungal degradation of PBAT. Moreover, the final rates of PBAT biodegradation in an inoculated compost with fungi and in a real compost were found comparable, which means that the selected fungi were efficient as much as a mixture of bacteria and fungi. The curves of PBAT biodegradation were modeled by Hill sigmoid. Fungal degradation was completed by investigating the physical and the chemical properties of the polymer during the process of degradation using several analytical methods such as matrix assisted laser desorption ionization-time of fly spectroscopy, size exclusion chromatography, and differential scanning calorimetry. These experiments led to a better understanding of the various stages of fungal degradation of PBAT: hydrolysis as well as mineralization. Furthermore, the analysis of metabolizing products was investigated also.

The biodegradability of polymers by microorganisms is generally studied in a real environment that contains a natural mixture of fungi and bacteria. The present research mainly focused on the purely fungal degradation of poly(l-lactide), PLLA, to enclose the part of fungi in a real process of biodegradation and to understand the kinetics of biodegradation. Respirometric tests were realized in soil at 30 °C, and in compost at 30 and 58 °C. Results indicated that temperature is the predominant parameter governing the fungal degradation of PLLA. Moreover, in real compost, the biodegradation kinetics of the PLLA revealed a synergy between bacteria and fungi. The curves of PLLA and cellulose biodegradation were modeled by Hill sigmoïd. Fungal degradation was completed by investigating the physical and the chemical properties of the polymer during the process of degradation using several analytical methods such as matrix assisted laser desorption ionization-time of fly spectroscopy, infrared spectroscopy, size exclusion chromatography, and differential scanning calorimetry. These experiments led to a better understanding of the various stages of fungal degradation of PLLA: hydrolysis as well as mineralization. Furthermore, metabolizing products (by-products) of PLLA was investigated also.

For many years now, scientific articles have been published on the potential biodegradability of polyethylene. Polyethylene (PE) with peroxidant additives, in the form of agricultural films, is sold by various suppliers as biodegradable mulch. Even though, the photo-chemical and thermal degradation of these products under artificial laboratory conditions is highlighted, several extrapolation on the biodegradation and, moreover, on the neutral environmental impact of PE are made. In this study, three different commercial mulch films have been submitted to standardised biodegradation tests and the results are discussed. The first conclusions are that a very low degree of biodegradation of the commercial PE films is achieved from these tests and that crosslinked PE micro-fragments are found in soil after a very long period of time.

A new automated set-up based on the original Sturm test was developed for determining the biodegadability of proteic mulching films. This method is based on the measurement of released (respiratory metabolism of microorganisms) carbon dioxide to determine film biodegradability. Maintenance of constant aerobic conditions in thermoregulated bioreactors and continuous measurement of released CO, with an infrared differential gas analyser were the main advantages of this set-up. It was verified with a plasticised proteic film that soil extracts could be used as microbial Sources instead of activated sludge that was usually used in laboratory biodegradation tests. (C) 2004 Academic des sciences. Published by Elsevier SAS. All rights reserved.

Résumé : La biodégradation du polyéthylène fait l'objet de nombreuses publications et d'une pression commerciale de plus en plus forte. Pourtant, une analyse scientifique des résultats publiés fait apparaître de nombreuses imprécisions, incohérences ou lacunes dans les démarches employées qui permettent de mettre e n doute la réelle biodégradabilité de c e polymère a dditivé. Les questions qui restent en suspens s ont clairement exposées et la prudence dans l'utilisation de ce polymère additivé en agriculture est vivement recommandée dans l'attente de résultats plus probants. Abstract : The biodegradation of polyethylene is the subject of numerous publications and, moreover, specifically designed PE is the object of a strong commercial pressure. However, a scientific a nalysis of the available results highlights various inaccuracies, inconsistencies and deficiencies in the experimental approaches which cast doubt the effective biodegradability of this polymer. Open questions are clearly raised and care must be taken in the agricultural use of these additived polymer in the wait of convincing results.