In vitro comparisons between Carica papaya and pancreatic lipases during test meal lipolysis: Potential use of CPL in enzyme replacement therapy

High levels of lipase activity are known to occur in Carica papaya latex, and this activity is being used in some biotechnological applications. The lipolytic activity of C. papaya lipase (CPL) on dietary triacylglycerols (TAG) has not yet been studied. Hence, the aim of this study was to characterise the specific activity of CPL on dietary TAG present in a crude preparation. Also, we have determined its stability during the lipolysis of a test meal at various pH values mimicking those occurring in the gastro-intestinal tract, with or without bile, and have compared these properties with those of porcine pancreatic extract (PPE) and human pancreatic lipase (HPL). CPL showed maximum stability at pH 6.0, both with and without bile. Some residual activity was still observed at pH 2 (20%), whereas the pancreatic lipases tested were immediately completely inactivated at this pH. In the absence of bile, the highest specific activities were measured at pH 6 in the case of CPL, PPE and HPL. Adding bile slightly decreased the CPL activity in the 4–6 pH range, thus shifting the optimum CPL activity to pH 7, where the presence of bile had no effect. Lipolysis levels decreased with the pH, but CPL was still more active than PPE at pH 5 on a relative basis. These results suggest that CPL might be a promising candidate for use as a therapeutic tool on patients with pancreatic exocrine insufficiency.     

Urban wastewater treatment by a nutrient film technique system with a valuable commercial plant species (Chrysanthemum cinerariaefolium Trev.)

Urban wastewater causes rapid eutrophication of natural waters and requires treatment before discharge. This is expensive and produces huge quantities of sludge. In the European Community, it will no longer be lawful to dispose of this sludge as landfill after 2005 (European Directive 91/271/CEE of May 21, 1991). Wastewater treatment by the Chrysanthemum cinerariaefolium plants in horizontal flow was investigated using the nutrient film technique (NFT), a widely used hydroponic system in the commercial greenhouse industry. After a 48 h plant treatment, the purification efficiency was 95%, 91%, and 99% with respect to suspended solids (SS), biochemical oxygen demand (BOD5), and chemical oxygen demand (COD), and the elimination of nutrients (total nitrogen and total phosphorus) varied between 40% and 80%. SS and thus indirectly BOD5 and COD were removed by filtration and adsorption; the solids trapped in the root systems were then decomposed and mineralized. The system with 25 plants purified 30 L of wastewater in 48 h. One-hundred people communities wastewater could be treated with a 6 m2 area of production. Pyrethrin contents and chlorophyll a fluorescence of plants grown on raw urban waters were not significantly different from those grown on a standard nutrient solution.     

Combining fuzzy querying of imprecise data and predictive microbiology using category-based reasoning for prediction of the possible microbial spoilage in foods: application to Listeria monocytogenes

Various predictive models of microbial behavior have been created and extensive data collection has been done by numerous private or public laboratories. However, significant differences between predicted and observed values in foods have been observed and need to be stressed, understood and explained as much as possible. In this paper, we present a software tool (currently at the level of a prototype) able: (i) to store in a database all relevant information expressed on one hand as qualitative or quantitative data and on the other hand as precise or imprecise data; (ii) to retrieve the more relevant information from the database using queries where criteria may be expressed as fuzzy values in order to enhance the flexibility of the search: (iii) to compute, in addition to the nearest data, an estimation of searched values using statistical models. The architecture of this software tool is structured as a category-based reasoning system. Example queries about Listeria monocytogenes (L. monocytogenes) illustrate the functionalities of this tool.     

Transport of Cryptosporidium oocysts in porous media: role of straining and physicochemical filtration

The transport and filtration behavior of Cryptosporidium parvum oocysts in columns packed with quartz sand was systematically examined under repulsive electrostatic conditions. An increase in solution ionic strength resulted in greater oocyst deposition rates despite theoretical predictions of a significant electrostatic energy barrier to deposition. Relatively high deposition rates obtained with both oocysts and polystyrene latex particles of comparable size at low ionic strength (1 mM) suggest that a physical mechanism may play a key role in oocyst removal. Supporting experiments conducted with latex particles of varying sizes, under very low ionic strength conditions where physicochemical filtration is negligible, clearly indicated that physical straining is an important capture mechanism. The results of this study indicate that irregularity of sand grain shape (verified by SEM imaging) contributes considerably to the straining potential of the porous medium. Hence, both straining and physicochemical filtration are expected to control the removal of C. parvum oocysts in settings typical of riverbank filtration, soil infiltration, and slow sand filtration. Because classic colloid filtration theory does not account for removal by straining, these observations have important implications with respect to predictions of oocyst transport.     

Wheat gluten-coated papers for bio-based food packaging: Structure,surface and transfer properties

The objective of the present work was to understand how the structural, surface, water vapour and gas barrier properties of wheat gluten (WG) coated paper could be influenced by the features of paper. For this purpose, a surface treated paper (TP) and an untreated paper (UTP) were compared. Penetration of WG-coating into the bulk of paper was more pronounced in UTP than TP. This led to the formation of a significant junction zone resulting in an interpenetrated structure for WG–UTP, suggesting a composite-like structure, while a bi-layer one was obtained for WG–TP. Differences in WG penetration were related to the hydrophilicity, roughness and porosity of the paper used. Even though the extent of penetration did not greatly affect the surface properties (water and oil resistance), the transfer properties (water vapour, O₂ and CO₂) of WG-coated papers were significantly improved when WG-coating highly penetrated: while the WG–TP behaved as a micro-perforated material, the WG–UTP behaved as WG-film.     

Individual cell lag time distributions of Cronobacter (Enterobacter sakazakii) and impact of pooling samples on its detection in powdered infant formula

Cells of six strains of Cronobacter were subjected to dry stress and stored for 2.5 months at ambient temperature. The individual cell lag time distributions of recovered cells were characterized at 25 °C and 37 °C in non-selective broth. The individual cell lag times were deduced from the times taken by cultures from individual cells to reach an optical density threshold. In parallel, growth curves for each strain at high contamination levels were determined in the same growth conditions. In general, the extreme value type II distribution with a shape parameter fixed to 5 (EVIIb) was the most effective at describing the 12 observed distributions of individual cell lag times. Recently, a model for characterizing individual cell lag time distribution from population growth parameters was developed for other food-borne pathogenic bacteria such as Listeria monocytogenes. We confirmed this model’s applicability to Cronobacter by comparing the mean and the standard deviation of individual cell lag times to populational lag times observed with high initial concentration experiments. We also validated the model in realistic conditions by studying growth in powdered infant formula decimally diluted in Buffered Peptone Water, which represents the first enrichment step of the standard detection method for Cronobacter. Individual lag times and the pooling of samples significantly affect detection performances.     

Evolution of Listeria populations in food samples undergoing enrichment culturing

The isolation of Listeria monocytogenes from food is carried out using a double enrichment. It is believed that the double enrichment can allow the overgrowth of Listeria innocua in samples where both species are present. In this study, we have evaluated the impact of overgrowth between Listeria species and strains during each step of the enrichment process. The effect of factors minimizing interactions between strains or phage inhibitory effects has also been estimated. In an artificially contaminated food undergoing enrichment, overgrowth could result from competitive interactions between Listeria spp. resulting from the production of bacteriocins and bacteriophage at high initial contamination levels (>10(4) cfu/g), but not at lower levels (50-100 cfu/g) as generally found in contaminated foods. At high levels of inoculation, the competitive effect could be reduced by solidification of the selective broths, to limit the diffusion of the inhibitors. Overgrowth resulting from differences in growth rate occurred independent of the initial contamination level. However, in naturally contaminated foods undergoing enrichment, there were no absolute correlations between growth rates or inhibitory profiles in terms of strain evolution during enrichment. In fact, Listeria strains which were predominant in the original sample in most cases remained the dominant strains at the end of the enrichment, although the relative proportion of any given strain could change significantly over the enrichment process. Additional factors which have yet to be identified impact on the evolution of Listeria in the two-step enrichment process. Analysis of strain evolution in eight naturally contaminated foods has indicated that the second enrichment step in Fraser broth can be reduced from 48 to 24 h without impacting on the recovery of L. monocytogenes. Our limited survey of naturally contaminated foods also demonstrated that maximum recovery of L. monocytogenes and other Listeria strains was found following 24 h incubation in 1/2 Fraser Broth. This finding suggests that it may be possible to shorten the current two-step isolation method further without reducing method sensitivity.     

Total lipid content, fatty acids and 4-desmethylsterols accumulation in developing fruit of Pistacia lentiscus L. growing wild in Tunisia

This research has determined oil, fatty acid and sterol contents of the Tunisian Pistacialentiscus (Lentisc) fruits during maturation. Low oil accumulation was observed during the first 35 days after the fruiting (DAF) date (from 1.83% to 2.57%). After that, two phases were distinguished (35th until the 60th and 105th to the 145th DAF), where the rate of oil accumulation increased significantly. At the last stage of maturation, the lentisc fruits had the highest percentage of lipid content, 42.54%. The changing profile of fatty acids during maturation had been marked mainly by an increase in oleic acid content (from 19.49% to 50.72%) paralleling a decrease in linoleic acid content (from 42.5% to 21.75%). At the 15th DAF, the alpha-linolenic acid was found with a maximum of 13.81%. At full maturity, the main fatty acids were oleic acid, followed by palmitic and linoleic acid. Other fatty acids were present in trace proportions, such as palmitoleic, stearic, linolenic, gadoleic and arachidic acid. In all stages of ripening only four sterols were identified and quantified. β-Sitosterol was the major 4-desmethylsterol in samples tested, followed by campesterol. Cholesterol and stigmasterol were detected in trace amounts. During the first stage of ripening, the amount of total sterols was about 5.19/100 g of oil. It decreased to 0.43/100 g in the last stage. Sitosterol and campesterol showed nearly the same profile during the ripening of P. lentiscus fruit which could be linked to the relation between these compounds during their biosynthesis.