Prediction studies of environment-friendly biodegradable polymeric packaging based on PLA. Influence of specimens' thickness on the hydrolytic degradation profile.

Application of new biodegradable polymer packaging based on polylactide (PLA), susceptible to organic recycling, can help in the waste reduction in landfills. In this paper, the results of the study on abiotic degradation of PLA and its blend containing 15 mol% of poly[(R,S)-3-hydroxybutyrate], as a model for the first step of organic recycling were presented. The samples used for this study have different shapes and thicknesses: rigid films and cuboid-bars. Particular emphasis was placed on determining the pattern of degradation products released into the medium. Originally, the results of present study revealed that the application of electrospray ionization mass spectrometry supported by high performance liquid chromatography allowed envisaging the differences in the degradation products pattern released from the studied PLA-based samples differing in thickness. The significant differences in degradation products pattern were predominately observed in the first steps of incubation process and are caused by an autocatalytic effect, which occurs mainly during degradation of the large size PLA samples. Although, the thickness of PLA-based packaging changes the degradation product patterns, however this does not increase the total amounts of acids released to the medium. Thus, it may be concluded that thickness should not affect significantly organic recycling of the packaging.

An isoenzyme survey of Trypanosoma cruzi genetic variability in sylvatic cycles from French Guiana.

Twenty-seven trypanosomatidae stocks isolated from various hosts in French Guiana have been surveyed by Multilocus Enzyme Electrophoresis on cellulose acetate plates. The variability observed at 22 different enzyme systems was considerable, since 21 different enzyme profiles (zymodemes) could be distinguished. Clustering analysis and comparison with four laboratory reference stocks showed clearly that three stocks were distantly related from the rest and most probably cannot be included in the species Trypanosoma cruzi. All the other stocks were more related to the formerly described zymodeme I than to the formerly described zymodemes II and III. Genotype variability in this T. cruzi sylvatic population was notably higher than in domestic populations of the same parasite. This could suggest more frequent genetic exchange occurring in sylvatic cycles. Nevertheless, a population genetic analysis of the data showed a considerable linkage disequilibrium, which rather favors the hypothesis that T. cruzi has a basically clonal population structure in this ecosystem too.