New Insight into Biodegradation of Polylactide (PLA)/Clay Nanocomposites Using Molecular Ecological Techniques Parveen Sangwan, Cameron Way, Dong-Yang Wu * Introduction Polylactide (PLA) is an environmental friendly, economical and commercially available polymer that can be produced from renewable resources such as sugarcane, potatoes and corn. [1,2] It is widely used in various medical applications for controlled drug delivery, medical implants and absorbable sutures. [3] It is biocompatible and biodegrad- able, and offers great potential as disposable packaging material. However, further improvements in mechanical strength, thermal stability, gas permeability etc. are required to allow its use as a sustainable alternative to synthetic non-biodegradable plastics in a broader range of applications in aerospace, automobiles and building construction. Development of polymer-layered silicate nanocompo- sites [4] has attracted significant research interests in recent years and it is considered as one of the effective means for improving properties of polymers including PLA. The concept was first explored by the Toyota group for preparation of nylon-layered silicates nanocomposites exhibiting significantly improved material properties. [5,6] Recent studies have reported that mechanical performance and the rate of biodegradation of PLA/organically modified layered silicates (OMLS) nanocomposites was significantly enhanced relative to neat PLA samples. [7–13] In these studies, assessment of polymer degradation was per- formed either by gravimetric analysis such as weight loss or respirometric measurement of total amount of CO 2 evolved during the biodegradation process. [8,9,11] While these methods provide an indication of the biodegrad- Full Paper P. Sangwan, C. Way, D.-Y. Wu CSIRO Materials Science and Engineering, Gate 5, Normanby Rd, Clayton South, Victoria 3168, Australia Fax: (þ61) 3 9545 2829; E-mail: dong.yang.wu@csiro.au Novel molecular ecological techniques were used to study changes in microbial community structure and population during degradation of polylactide (PLA)/organically modified layered silicates (OMLS) nanocomposites. Cloned gene sequences belonging to members of the phyla Actinobacteria and Ascomycota comprized the most dominant groups of microorganisms during biodegradation of PLA/OMLS nanocom- posites. Due to their numerical abundance, members of these microbial groups are likely to play an important role during biodegrada- tion process. This paper presents new insights into the biodegradability of PLA/OMLS nano- composites and highlights the importance of using novel molecular ecological techniques for in situ identification of new microorgan- isms involved in biodegradation of polymeric materials. Macromol. Biosci. 2009, 9, 000–000 ß 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mabi.200800276 1 Early View Publication; these are NOT the final page numbers, use DOI for citation !! R