Lipase-catalyzed synthesis of hydrophobically modified dextrans: activity and regioselectivity of lipase from Candida rugosa

Vinyl decanoate-modified dextran macromolecules (DexT40-VD) were synthesized in dimethyl sulfoxide at 50°C using lipase AY from Candida rugosa for catalyzing transesterification between polysaccharide and vinyl fatty esters. The extent of dextran modification (quantified by the molar ratio of attached alkyl tails to sugar repeat units) with native-, pH-adjusted-, 18-crown-6 ether pretreated pH-adjusted-, and stepwise addition of pretreated lipase AY yielded <3%, 49%, 64% and 96% modified dextran respectively. Lipase AY accelerated the transesterification of DexT40 from 2- to 63-fold higher than the non-catalyzed system. This procedure was extended to other acyl donors showing that modification pattern exhibited regioselectivity depending on acyl donor structure. Regioselectivity equaled between 2- and 3-OH with saturated fatty acyl donors. The 2-OH was favored for unsaturated fatty acyl donors, while sterically hindered acyl donors oriented modification toward 3-OH position. DexT40-VD at 96% modification was a water-insoluble polymer forming 150nm diameter nanoparticles in water which can be used as drug carrier systems.     

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.     

Inactivation of Escherichia coli and Listeria innocua in kiwifruit and pineapple juices by high hydrostatic pressure

Escherichia coli and Listeria innocua in kiwifruit and pineapple juices were exposed to high hydrostatic pressure (HHP) at 300 MPa for 5 min. Both bacteria showed equal resistance to HHP. Using low (0 degrees C) or sub-zero (-10 degrees C) temperatures instead of room temperature (20 degrees C) during pressurization did not change the effectiveness of HHP treatment on both bacteria in studied juices. Pulse pressure treatment (multiple pulses for a total holding time of 5 min at 300 MPa) instead of continuous (single pulse) treatment had no significant (p>0.05) effect on the microbial inactivation in kiwifruit juice; however, in pineapple juice pulse treatment, especially after 5 pulses, increased the inactivation significantly (p<0.05) for both bacteria. Following storage of pressure-treated (350 MPa, 20 degrees C for 60 s x 5 pulses) juices at 4, 20 and 37 degrees C up to 3 weeks, the level of microbial inactivation further increased and no injury recovery of the bacteria were detected. This work has shown that HHP treatment can be used to inactivate E. coli and L. innocua in kiwifruit and pineapple juices at lower pressure values at room temperature than the conditions used in commercial applications (>400 MPa). However, storage period and temperature should carefully be optimized to increase the safety of HHP treated fruit juices.     

Quantitative Evaluation of Thermal Inactivation Kinetics of Free-Floating Versus Surface-Attached Listeria innocua Cells

Surface pasteurization is one of the decontamination treatments that can contribute to better preservation of meat products retaining most of their quality characteristics relatively intact if compared with the raw products. The current research compares the kinetics of free-floating and surface attached Listeria innocua cells by using integrated microbial and heat transfer modelling approaches. Surface pasteurization treatments are applied on a (abiotic) Teflon® model system in a novel steam surface decontamination rig. The experimental set-up prevented following four technological aspects to occur, (1) cold purge migration to the surface during the heating process, (2) inactivation kinetics of a cocktail of microbes, (3) protective effect of food components, and (4) physical distribution of bacteria throughout the depth of the product skin. Microbial load predictions are performed based on the inactivation parameters obtained during free-floating cell experiments. These predictions, when compared with the microbial data of the surface treatments, prove that the surface attached cells were much more heat resistant, despite the experimental set-up preventing the aforementioned (technological) events to occur. Indeed, surface attached cells can have different physiological/phenotypical/genetical characteristics, such as cell aggregations, colony formations, presence of flagella. In a final step, three techniques are implemented to evaluate mathematically the kinetics of the surface attached cells. Overall, this research’s significance is lying in the quantitative assessment of microbial heat resistance. The technological reasons underlying the increased microbial heat resistance on biotic and abiotic surfaces should be reevaluated, taking into account possible physiological/phenotypical/genetical characteristics.     

UF resin efficiency of MDF as affected by resin content loss, coverage level and pre-cure

A full-factorial experimental design was used to investigate the effects of three factors on UF resin efficiency. Within the limits of this study, the three factors, namely, resin content loss, resin coverage level and resin pre-cure time for mechanical blended MDF fibres were found to have significant effects on resin efficiency as evaluated by the internal bond strength (IB) of the panels. The most significant factor was resin content loss followed by resin coverage level and resin pre-cure. The resin coverage level had a positive effect on resin efficiency, while the resin content loss, resin pre-cure time at 40 °C conditions, the interactions of resin coverage level and resin content loss as well as resin coverage level with pre-cure had negative effects on resin efficiency. For a given resin content, the resin efficiency could be increased by 35% by increasing the level of resin coverage. The resin efficiency obviously decreased with resin content loss and pre-cure time.

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Beeinflussung der UF-Harzwirksamkeit bei MDF durch Harzverlust, Harzverteilungsgrad und Harzvorhärtung

Zusammenfassung In einem vollständig faktoriell angelegten Versuch wurde die Wirkung der drei Faktoren Harzverlust, Harzverteilungsgrad und Harzvorhärtung auf die UF-Harzwirksamkeit untersucht. Im Rahmen dieser Studie zeigte sich anhand der Bewertung der Querzugfestigkeit (IB) der Platten, dass sich diese drei Faktoren erheblich auf die Harzwirksamkeit bei mechanisch durchmischten MDF-Fasern auswirken. Der bedeutendste Faktor war Harzverlust gefolgt von Harzverteilungsgrad und Harzvorhärtung. Der Harzverteilungsgrad wirkte sich auf die Harzwirksamkeit positiv aus. Dagegen wirkten sich Harzverlust, Harzvorhärtungszeit bei einer Temperatur von 40 °C, sowie die gemischten Glieder aus Harzverteilungsgrad und Harzverlust sowie aus Harzverteilungsgrad und Vorhärtung negativ auf die Harzwirksamkeit aus. Durch eine verbesserte Harzverteilung konnte die Harzwirksamkeit bei gegebenem Harzgehalt um 35% erhöht werden. Die Harzwirksamkeit nimmt offensichtlich mit zunehmendem Harzverlust und Vorhärtungszeit ab.

     

In vitro interactions between DMSA-coated maghemite nanoparticles and human fibroblasts: A physicochemical and cyto-genotoxical study

Although the current production of oxide nanoparticles may be modest, the wide range of proposed applications and forecasted growth in production has raised questions about the potential impact of these nanoparticles on the environment and human health. Iron oxide nanoparticles have been proposed for an increasing number of biomedical applications although in vitro toxicity depending on the particles coating has been evidenced. The aim of this study was to examine the potential in vitro cyto- and genotoxicity on human dermal fibroblasts of DMSA-coated maghemite nanoparticles (NmDMSA) as a function of well-defined physicochemical states. Well-stabilized NmDMSA produced weak cytotoxic and no genotoxic effects. This is attributed in part to the DMSA coating, which serves as a barrier for a direct contact between nano-oxide and fibroblasts, inhibiting a potential toxic effect.     

Cassava retting: Optimisation of a traditional fermentation by an experimental research methodology

Retting, a spontaneous and traditional fermentation of cassava roots in Central Africa, was optimised in terms of time and the quality of the end-product. Optimal conditions were achieved by using an experimental research methodology. Temperature is the most influential factor, with an optimum of 34°C for quicker retting. The roots should be peeled and soaked in water immediately after harvesting to increase the quality of cassava foods. Inoculation of water with juice from a prior retting helps in cassava detoxification but has no influence on the time or the quality of foo-foo. Foo-foo samples had the most favourable organoleptic quality when an incubation temperature of between 28 and 37°C was used. Using optimal conditions, retting time was reduced 3-fold, and foo-foo of high and constant quality could be processed.     

Tailor made OSB for special application

The purpose of this study was to develop speciality oriented strand board (OSB) with high stiffness for use in products such as engineered wood flooring (EWF). Three-layer oriented strand boards were manufactured from two feedstocks of strands: a mixture of 90% aspen (Populus tremuloides) and 10% of paper birch (Betula papyrifera), and 100% of small diameter ponderosa pine logs (Pinus ponderosa). The OSB panels were manufactured under a factorial design of three resin contents, two density profiles, and three weight ratios for the face and core layers. Tests to determine density, bending modulus of elasticity (MOE), internal bond (IB) and thickness swelling (TS) were performed according to ASTM standard D 1037-06a. The results showed that the higher values of bending MOE for panels made from aspen/birch mixture and ponderosa pine, 8190 and 9050?MPa, respectively, were obtained for the same combination of factors. Such high bending MOE values are very close to Baltic birch (Betula pendula) plywood, a product known for its high stiffness. The effect of resin content on IB is more pronounced for panels made from ponderosa pine than panels made from the aspen/birch mixture. Thickness swelling of panels made from ponderosa pine strands is higher than thickness swelling of panels made from a mixture of aspen and birch strands. The results indicate the potential to tailor an OSB for a specific application such as EWF.     

In vitro inhibitory effect of tetrahydrocurcuminoids on Fusarium proliferatum growth and fumonisin B₁ biosynthesis

Many plant pathogens produce toxic metabolites when growing on food and feed. Some antioxidative components seem to prevent fungal growth and mycotoxin formation. Recently, we synthesized a new class of powerful antioxidative compounds, i.e. tetrahydrocurcuminoids, and its structure/antioxidant activity relationships have been established. The South West of France produces large amounts of corn, which can be infected by Fusarium species, particularly F. proliferatum. In this context, the efficiency of tetrahydrocurcuminoids, which can be obtained from natural curcuminoids, was investigated to control in vitro the growth of F. proliferatum and the production of its associated mycotoxin, fumonisin B?. The relation between structure and antifungal activity was studied. Tetrahydrocurcumin (THC1), with two guaiacyl phenolic subunits, showed the highest inhibitory activity (measured as radial growth on agar medium) against the F. proliferatum development (67% inhibition at a concentration of 13.6 μmol ml?1). The efficiencies of THC2 (36% at a concentration of 11.5 μmol ml?1), which contains syringyl phenolic units, and THC3 (30% at a concentration of 13.6 μmol ml?1), which does not have any substituent on the aromatic rings, were relatively close. These results indicate that the simultaneous presence of guaiacyl phenols and the enolic function of the β-diketone moiety play an important role in the inhibition mechanisms. The importance of this combination was confirmed using n-propylguaiacol and acetylacetone as molecular models. Under the same conditions, ferulic acid and eugenol, other natural phenolic antioxidants, were less efficient in inhibiting fungal growth. THC1 also reduced fumonisin B? production in liquid medium by approximately 35, 50 and 75% at concentrations of 0.8, 1.3, and 1.9 μmol ml?1, respectively. These very low inhibitory concentrations show that tetrahydrocurcuminoids could be one of the most promising biobased molecules for the control of mycotoxinogen fungal strains.     

Forecast of mycotoxins levels in soft wheat, durum wheat and maize before harvesting with Qualim��tre?

Some mycotoxins are produced by several Fusarium species during cultivation and are found in wheat and maize grain. Since 2000, Syngenta has organised a large field survey. Agronomic and climatic data and grain samples have been collected for mycotoxin analysis in France and Belgium. The importance of the agroclimatic factors and their interactions on the mycotoxin levels in grain has been estimated. The climate around flowering stage is the major factor for deoxynivalenol (DON) in wheat. The main agronomic criteria are residue management and the variety sensitivity to this mycotoxin. For DON, zearalenone and fumonisins in maize, the climate from flowering stage until harvest is the major factor. Then, according to each mycotoxin, the main agronomic criteria are the harvest condition (date and grain moisture), the corn borer infestation and the variety sensitivity to these mycotoxins. Over the years, the database has been used to define models to predict the mycotoxin risk before harvesting. Grain purchasers enter the required agronomic data via the Syngenta Internet site and define their grain purchasing areas. They also define the flowering period for wheat and corn borer infestation for maize. After calculation which integrates climatic data, the purchasers receive reports with forecasts of mycotoxin levels. Prediction is based on different agro-climatic statistical models specifically configured according to the different regions of production in France and Belgium. This approach is called Qualimètre^? and was the first service in France and Belgium to forecast the grain mycotoxin level for wheat in 2004 and maize in 2006.