Antimicrobial nanostructured starch based films for packaging.

Montmorillonite modified with a quaternary ammonium salt C30B/starch nanocomposite (C30B/ST-NC), silver nanoparticles/starch nanocomposite (Ag-NPs/ST-NC) and both silver nanoparticles/C30B/starch nanocomposites (Ag-NPs/C30B/ST-NC) films were produced. The nanoclay (C30B) was dispersed in a starch solution using an ultrasonic probe. Different concentrations of Ag-NPs (0.3, 0.5, 0.8 and 1.0mM) were synthesized directly in starch and in clay/starch solutions via chemical reduction method. Dispersion of C30B silicate layers and Ag-NPs in ST films characterized by X-ray and scanning electron microscopy showed that the presence of Ag-NPs enhanced clay dispersion. Color and opacity measurements, barrier properties (water vapor and oxygen permeabilities), dynamic mechanical analysis and contact angle were evaluated and related with the incorporation of C30B and Ag-NPs. Films presented antimicrobial activity against Staphylococcus aureus, Escherichia coli and Candida albicans without significant differences between Ag-NPs concentrations. The migration of components from the nanostructured starch films, assessed by food contact tests, was minor and under the legal limits. These results indicated that the starch films incorporated with C30B and Ag-NPs have potential to be used as packaging nanostructured material.

Biodegradation assessment of PLA and its nanocomposites.

Poly(lactic acid) nanocomposites containing Cloisite 15A, Cloisite 30B, and Dellite 43B were prepared by melt-mixing in a batch mixer and were exposed to UV radiation, temperature, and microorganism in solution and in a compost. Exposed samples, collected along the time, were characterized by several techniques. While the addition of organoclays had a positive effect on thermal stability, the degradation rate of nanocomposites increased when exposed to UV radiation and microorganism. Moreover, the degradation rate depends on the organoclay type. Even though the degradation rate is higher for nanocomposites, Fourier transform infrared spectrometry and gel permeation chromatography results demonstrated that the degradation mechanism is the same.

Use of biopolymers as solid substrates for denitrification.

The conventional process to remove nitrate from water, the biological denitrification, uses the addition of dissolved organic carbon that has the potential risk to further deteriorate water quality. Thus, this work aimed to evaluate the specific denitrification activity of a mixed microbial culture and a pure culture of Pseudomonas stutzeri with solid substrates such as polycaprolactone (PCL), polylactic acid (PLA), and starch. The highest nitrate reduction activity was obtained with a microbial mixed culture using starch, 104 mg N(2)-N/(g VSS.d), and PCL, 97 mg N(2)-N/(g VSS.d), followed by PLA, 53 mg N(2)-N/(g VSS.d). A considerable advantage of using biopolymers in water denitrification is the reduced risk of contaminating the water with soluble biodegradable organic carbon.

Removal of phosphorus from water using active barriers: Al2O3 immobilized on to polyolefins.

Phosphorus is known to contribute to eutrophication of fresh water systems, as generally it is the limiting nutrient controlling algae growth. Laboratory studies were conducted to develop and test active barriers composed of aluminium oxide immobilized on to polyolefins to remove phosphorus from water. For this purpose, flat plates of polyethylene and polyethylene grafted with maleic anhydride were prepared and tested. The adsorption mechanism of phosphorus on to aluminium oxide was described by the Freundlich isotherm. The optimum pH interval for phosphorus removal was between 5.2 and 7.8, which includes the pH of natural waters. The maximum phosphorus removal capacity was around 11.1 microg/cm2 for both active barriers. Both barriers removed more than 90% of phosphorus from a 100 mirog/L solution in a static batch experiment carried out for 90 d. The in situ implementation of the active barriers developed in the present study might be a valuable strategy to sequester phosphate and thus to control eutrophication in natural ecosystems, though further work is required to evaluate possible interferences coming from other substances present in the water.

Characterization of biofilm formation on a humic material.

Biofilms are major sites of carbon cycling in streams. Therefore, it is crucial to improve knowledge about biofilms' structure and microbial composition to understand their contribution in the self-purification of surface water. The present work intends to study biofilm formation in the presence of humic substances (HSs) as a carbon source. Two biofilm flowcells were operated in parallel; one with synthetic stream water, displaying a background carbon concentration of 1.26+/-0.84 mg L(-1), the other with added HSs and an overall carbon concentration of 9.68+/-1.00 mg L(-1). From the biofilms' results of culturable and total countable cells, it can be concluded that the presence of HSs did not significantly enhance the biofilm cell density. However, the biofilm formed in the presence of HSs presented slightly higher values of volatile suspended solids (VSS) and protein. One possible explanation for this result is that HSs adsorbed to the polymeric matrix of the biofilm and were included in the quantification of VSS and protein. The microbial composition of the biofilm with addition of HSs was characterized by the presence of bacteria belonging to beta-Proteobacteria, Cupriavidus metallidurans and several species of the genus Ralstonia were identified, and gamma-Proteobacteria, represented by Escherichia coli. In the biofilm formed without HSs addition beta-Proteobacteria, represented by the species Variovorax paradoxus, and bacteria belonging to the group Bacteroidetes were detected. In conclusion, the presence of HSs did not significantly enhance biofilm cell density but influenced the bacterial diversity in the biofilm.

[Antenatal diagnosis of a choledocal cyst]. / Diagnostic anténatal du kyste du cholédoque.

Choledocal cyst is a rare anomaly that usually becomes symptomatic during childhood. Forty to sixty percent of choledocal cysts are diagnosed before 10 years old, usually when complications occur. Today, because of advances in sonographic imaging, some cysts can de diagnosed before birth. The major prognostic factor is the development of complications such as hepatic fibrosis. Early treatment, after postnatal ultrasonography assessment, can reduce the incidence of serious complications. The authors report a case of a choledocal cyst diagnosed at 23 weeks gestation.