Development of plasticized edible films from Opuntia ficus-indica mucilage: A comparative study of various polyol plasticizers.

Mucilage polysaccharide was extracted from Opuntia ficus-indica cladodes (Cactaceae) and its composition was determined by sugar analysis using HPLC-RID and its structural features were elucidated by FTIR and 1H and 13C NMR. Films from the extracted mucilage were loaded at 40% (w/w) with glycerol, sorbitol, PEG 200 or PEG 400. The physical, thermal, mechanical and barrier properties of the obtained films were investigated. The highest water vapor barrier properties of plasticized mucilage films were obtained with sorbitol reaching water vapor permeability (WVP) values up to 3 times lower than the other films. The tensile strength (TS) values of films plasticized with PEG 200 and sorbitol were about 2 times higher than those of glycerol-plasticized films. The significant effect of polyol type plasticizers on the different properties of mucilage edible films was related to their structural features that promote different interactions with mucilage polysaccharides as demonstrated by FTIR and thermal properties.

Removal of Penicillin G and Erythromycin with Ionizing Radiation Followed by Biological Treatment.

The decomposition of penicillin G and erythromycin antibiotics at concentration of 0.2 mg ml(-1) by gamma irradiation at 50 kGy followed by biological treatment with Cupriavidus metallidurans CH34 was evaluated. Degradation of penicillin G and erythromycin was analyzed using nuclear magnetic resonance analysis (NMR), fourier transform infrared spectroscopy (FTIR), and chemical oxygen demand (COD). The exposure to the absorbed dose of 50 kGy caused degradation of penicillin G and erythromycin in the aqueous solution. The complete disappearance of NMR and FTIR peaks following irradiation confirmed the breakage of the ß-lactam ring in penicillin G, and the decarboxylation and cleavage of the thiazolidine ring and for erythromycin, the complete destruction of the three aromatic rings. Irradiation alone removed 52.8 and 65.5 % of penicillin G and erythromycin, respectively. Further reduction to 12.6 and 14 % of the original penicillin G and erythromycin COD, respectively, was achieved using treatment of the irradiation products with C. metallidurans.

Penta- and 2,4,6-tri-chlorophenol biodegradation during municipal solid waste anaerobic digestion.

In this study isotopic tracing using (13)C labelled pentachlorophenol (PCP) and 2,4,6-trichlorophenol (2,4,6-TCP) is proposed as a tool to distinguish the loss of PCP and 2,4,6-TCP due to biodegradation from other physical processes. This isotopic approach was applied to accurately assess in situ PCP and 2,4,6-TCP degradation under methanogenic conditions in several microcosms made up of household waste. These microcosms were incubated in anaerobic conditions at 35°C (mesophilic) and 55°C (thermophilic) without agitation. The volume of biogas produced (CH4 and CO2), was followed for a period of 130 days. At this stage of stable methanogenesis, (13)C6-PCP and (13)C6-2,4,6-TCP were introduced anaerobically in microcosms and its monitoring at mesophilic and thermophilic conditions was performed in parallel by gas chromatography mass spectrometry (GC-MS) and gas chromatography isotope-ratio mass spectrometry (GC-IRMS). This study proved the almost total dechlorination of bioavailable PCP and 2,4,6-TCP into 4-CP at 35°C. Nevertheless, high rate adsorption in particular materials of the two compounds was observed. Furthermore, Carbon-13 Nuclear Magnetic Resonance ((13)C-NMR) Spectroscopy analysis of (13)C labelled 2,4,6-TCP mesophilic incubations showed the partial mineralization of 4-CP at 35°C to acetate and then to HCO(3-). Consequently, NMR results confirm the biogas isotopic results indicating the mineralization of (13)C labelled 2,4,6-TCP into (13)C (CH4 and CO2). Concerning (13)C labelled PCP mesophilic incubations, the isotopic composition of the biogas still natural until the day 262. In contrast, no dechlorination was observed at 55°C. Thus PCP and 2,4,6-TCP were persistent in thermophilic conditions.

Evaluation of biodegradability of phenol and bisphenol A during mesophilic and thermophilic municipal solid waste anaerobic digestion using 13C-labeled contaminants.

In this paper, the isotopic tracing using (13)C-labeled phenol and bisphenol A was used to study their biodegradation during anaerobic digestion of municipal solid waste. Microcosms were incubated anaerobically at 35 °C (mesophilic conditions) and 55 °C (thermophilic conditions) without steering. A continuous follow-up of the production of biogas (CH(4) and CO(2)), was carried out during 130 d until the establishment of stable methanogenesis. Then (13)C(12)-BPA, and (13)C(6)-phenol were injected in microcosms and the follow-up of their degradation was performed simultaneously by gas chromatography isotope-ratio mass spectrometry (GC-IRMS) and gas chromatography mass spectrometry (GC-MS). Moreover, Carbon-13 Nuclear Magnetic Resonance ((13)C-NMR) Spectroscopy is used in the identification of metabolites. This study proves that the mineralization of phenol to CO(2) and CH(4) occurs during anaerobic digestion both in mesophilic and thermophilic conditions with similar kinetics. In mesophilic condition phenol degradation occurs through the benzoic acid pathway. In thermophilic condition it was not possible to identify the complete metabolic pathway as only acetate was identified as metabolite. Our results suggest that mineralization of phenol under thermophilic condition is instantaneous explaining why metabolites are not observed as they do not accumulate. No biodegradation of BPA was observed.