Detection of spoilage-causing yeasts and bacteria in tchapalo, the Ivorian traditional sorghum beer.

In this study, we aimed to analyse the spoilage potential of the isolated yeast, LAB and AAB species. Thus, 11 strains were inoculated at 0·3% (v/v) into a sterile filtered tchapalo and stored for 3 days at ambient temperature (27-30°C). All the tested strains grew well or remained stable except for Limosilactobacillus fermentum and Pediococcus acidilactici, which decreased throughout the storage time. A significant decrease of total soluble solids was observed only for Saccharomyces cerevisiae (from 7·8 to 5·8 °Brix) and Meyerozyma guilliermondii (from 7·8 to 5·5 °Brix). The tchapalo samples inoculated with the LAB strains Weissella paramesenteroides, P. acidilactici, L. fermentum and the yeast strain Candida tropicalis were judged similar to the control by the panellists. However, the strains of Lacticaseibacillus paracasei and Latilactobacillus curvatus (LAB), S. cerevisiae, M. guilliermondii and Kluyveromyces marxianus (yeasts) and Acetobacter pasteurianus and A. cerevisiae (AAB) induced the spoilage of the tchapalo appearance, smell and/or taste. In the spoiled tchapalo quantitative and qualitative modification of some volatile compounds (VOCs), such as lilac aldehyde, ethyl acetate, ethyl hexanoate, ethyl octanoate and phenethyl acetate, were observed. These results provide information about the microorganisms that need to be removed to extend the shelf life of tchapalo.

Bioaccessibility of polycyclic aromatic compounds (PAHs, PCBs) and trace elements: Influencing factors and determination in a river sediment core.

Organic matter (OM), clays, sand or time are factors possibly influencing the bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs) from sediments. An experimental design was performed to monitor and quantify this process. The bioaccessible fraction, linked to the rapidly-desorbing fraction (Frap) of contaminants, was assessed through a non-exhaustive extraction using a carboxymethyl-ß-cyclodextrin polymer. OM content was the most influential factor as regards Frap. Clay percentage was a slightly influential factor for PAHs while the interaction sand × OM was a slightly influential factor for PCBs. Frap was also determined in a sediment core collected from Martot's Pond (France). The higher the PAH/PCB concentration in this sediment, the higher the bioaccessible fraction. The relationship between a lower bioaccessibility and a higher number of PAHs cycles or PCB chlorines was linear. OM content impacted on Frap only for PAHs. Sequential extractions of some trace elements were also performed to evaluate their mobility. Cu, Cr, Pb, Ni were the less bioaccessible. A great part of As, Cd and Zn was found in the most bioaccessible sediment fractions. The 40-65 cm section might be considered as the most negatively impacting on the aquatic fauna, due to Cd and Zn high bioaccessible concentrations.

Influence of the vegetative cover on the fate of trace metals in retention systems simulating roadside infiltration swales.

Large-scale outdoor mesocosms were designed and co-contaminated with metals (Cd, Pb, Zn) and organic compounds to better understand the complex functioning of urban roadside swale environments. Infiltration systems were planted with macrophytes (P. arundinaceae, J. effusus and I. pseudacorus) or grassed, and natural or spiked target metals were monitored over two years. In the non-spiked mesocosms, atmospheric metal inputs were slightly higher than outputs, leading to low metal accumulation in topsoils and to very low outflow water contamination (<0.7% of the initial metal stock). In the spiked infiltration systems that simulated point pollution through water inflow, transfer of the initial stock of metals to the deeper soil layers was quite low and outflow water contamination was very low (<0.6% of the initial stock). The main metal output from these systems occurred in the first days of their installation because of the high metal solubility in water and insufficient plant cover at that time. The infiltration systems stabilized after a few weeks, probably because of stronger sorption to soil aggregates, and because of plant root development. Mephytoextraction in plant roots was more efficient in mesocosms planted with P. arundinacea and grass. Metal phytoextraction in plant aerial parts was also better for grass and P. arundinacea, when considering metal standing stocks instead of their concentration in plants. J. effusus was a good metal accumulator, but its low aboveground biomass development was less favorable to metal removal through harvesting.

Assessment of PAH dissipation processes in large-scale outdoor mesocosms simulating vegetated road-side swales.

Biofilters have been implemented in urban areas due to their ability to improve road runoff quality. However, little is known about the role of soil microorganisms and plants on pollutant remediation in planted swales. Therefore, four large-scale outdoor mesocosms were built and co-contaminated with metals and model polycyclic aromatic hydrocarbons (PAHs) (phenanthrene (Phen), pyrene (Pyr) and benzo[a]pyrene (BaP)), to better understand the complex functioning of swale-like environments. Three macrophyte plant species were tested for enhanced remediation of PAHs: Juncus effusus, Iris pseudacorus, Phalaris arundinacea and a grass mix. Long-term dynamics of PAHs in water outflow and soil was studied. Results showed that only 0.07 to 0.22% of total PAHs were released in water outflow after one year. Two years after contamination, soil sample analyses showed a dissipation of 99.6% for Phen and 99.4% for Pyr whatever the mesocosm considered and ranging from 75.5 to 91% for BaP, depending on plant species. Furthermore, dissipation time-courses may be described by a biphasic process. Experiments showed that the grass mix facilitated BaP long-term biodegradation. Grass appeared also to be the best filter for suspended solids because of its dense rhizosphere, which prevents the transfer of BaP to groundwater.

Evaluation of the PAH and water-extractable phenols content in used cross ties from the French rail network.

Recycling used railway sleepers is a major economic and environmental issue since nearly 50000 tons of those are incinerated every year in France. Therefore, it appeared essential to determine the real toxicity of sleepers and particularly for very old one. They are treated with creosote, which contains toxic and carcinogen compounds such as polycyclic aromatic hydrocarbons (PAHs). This study aims at measuring the amount of 16 priority PAHs and water extractable phenols in 12 sleepers implemented between 1936 and 1978. Results showed that the creosote content was systematically far above 1000mgkg(-1), even after 76years ageing. Crossties should then be considered as a hazardous waste according to European regulations. Less creosote and PAHs were detected in the sleepers centers. Moreover, the fraction of volatile PAHs was lower in the surface part, due to their evaporation. It appeared that a long ageing process was not sufficient to remove the major part of volatile PAHs and that they could be yet released in the atmospheric environment. Moreover, most of the treated crossties contained huge amount of the highly toxic benzo[a]pyrene, between 179mgkg(-1) and up to 853mgkg(-1) in wood. In contrast, the study revealed that concentrations of water extractable phenols were well below European regulations (3% by mass of creosote).