Development and validation of a multi-residue extraction method for the determination of organic micropollutants in surface water

The water pollution assessment to evaluate environmental quality standard on compliance with European Directive 2013/39/EU needs complex analytical approaches to satisfy legislation requirements about quantification of a wide range of pollutants, with different physicochemical properties and concentration levels (trace or ultra-trace). To accomplish this task, a multi-residue method for screening, quantification and confirmation of multiclass pollutants in surface water has been developed. It is based on an integrated approach where solid phase extraction (SPE), gas chromatography–mass spectrometry (GC–MS), gas chromatography–tandem mass spectrometry (GC–MS/MS) and liquid chromatography– tandem mass spectrometry (LC–MS/MS) are simultaneously employed. Target compounds, including several groups of emerging and persistent contaminants (as defined in the 2000/60/EC European Water Framework Directive) and, specifically, polycyclic aromatic hydrocarbons (PAH), phthalate, alkylphenols, polybrominated biphenyl ethers (PBDE), chlorophenols and chloroalkanes were investigated. The multi-residual method was validated according to DLG n°19/2010 with regards to two different concentration levels. According to the Environmental Quality Standard (EQS) they are defined as (i) the maximum concentration of a substance in natural water that does not affect the quality of water and (ii) the limit of quantification (LOQ), which must be lower than 1/3 of EQS. Recovery rates of SPE were from 62 to 105%. Precision of method, calculated as relative standard deviation (RSD), was below 27% for most of tested compounds. In conclusion, this method allows for rapid and reliable determination of different classes of organic micropollutants present at trace and ultra-trace levels in complex water matrices, such as surface water

Effects of two different sourdoughs on the characteristics of Pandoro, a typical Italian sweet leavened baked good

Pandoro is a traditional Italian sweet-leavened baked product, usually consumed at Christmas. It is manufactured according to specific procedures and preparation starts from a sourdough called \u2018\u2018madre\u2019\u2019 (mother sponge) continuously refreshed. This sourdough is the result of a complex microbial association including yeasts and lactic acid bacteria (LAB) and its use can improve sensory quality and shelf-life of the resulting products. The aim of this work was to evaluate the effect of the use of two different sourdoughs matured at different temperature (13 and 19 C) on some metabolites, which can affect the organoleptic characteristics of Pandoro. Different samples, taken throughout the 19 h of process, were analysed for the determination of yeast and LAB counts, pH, aw, carbohydrates, organic acids content and volatile profile. The results showed that, at the end of fermentation process, the sourdough propagated at 19 C reached lower pH values than that at 13 C. This was probably due to higher LAB counts (1 log unit higher), resulting also in higher lactic acid concentration and faster sugars depletion. On the contrary, temperature of dough during maturation did not affected yeast concentrations. Different production processes strongly affected also the volatile profile, both of sourdough at the end of fermentation and of the final products

In vitro tyramine accumulation by different strains of lactic acid bacteria

Tyramine poisoning is caused by consuming of food with high level of tyramine (TY). This biogenic amine is produced through the tyrosine decarboxylation by tyrosine decarboxylase (TDC) enzyme derived by Gram-positive bacteria in food, especially Lactic Acid Bacteria (LAB). Bacterial TDC is reported to be also able to decarboxylate phenylalanine to produce another biogenic amine, namely phenylethylamine (PEA). The aim of this work was to study the ability to accumulate tyramine in model systems by different LAB strains, possessing the tyrosine decarboxylase (tdcA) gene. Lactobacillus brevis LB42, Lactobacillus rhamnosus C1112, Lactobacillus paraplantarum DBT 1411, Lactobacillus fermentum RAF15800, Enterococcus faecalis EF37, Enterococcus faecalis ATCC 29212 and Streptococcus thermophilus 1TT45 were grown in standard broth (namely MRS for Lactobacillus, M17 for Streptococcus and BHI for Enterococcus) and in Bover-Cid broth medium, added or not with 0.1% (w/v) of tyrosine and incubated at 37\ub0C for 144 hours. Their growth curve were measured by optical density (DO at 600 nm) while their ability to accumulate tyramine were detected by HPLC analysis. All the tested strains were able to produce high levels of tyramine in all the conditions, with the exception of L. paraplantarum DBT1411 and L. fermentum RAF15800, which could accumulate very small amounts of this biogenic amine only after 144 hours in broths added with 0.1% (w/v) of tyrosine. Tyramine concentration increased concomitantly with the cell number with a relatively small further rise during the stationary phase. For all the tested strains the maximum level of tyramine (more than 500 mg/L) was reached in poor acidified medium added with tyrosine, except for L. rhamnosus C1112 which accumulate this compound with the same kinetics in MRS and in Bover-Cid medium. Moreover, the results showed that E. faecalis EF37, S. thermophilus 1TT45 and L. rhamnosus C1112 could accumulate also 2-phenylethylamine. In particular, E. faecalis EF37 produced more than 400 mg/L and 200 mg/L of this amine even after 48 hours of incubation in BHI and in Bover Cid (added with 0.1% tyrosine), respectively. The presence of LAB tyrosine decarboxylase positive strains in fermented food can be dangerous and the health risks associated with tyramine (also known as \u201ccheese reaction\u201d) should be avoided by using pure starter cultures without TDC. In addition, a deeper knowledge of TDC diffusion among the LAB having a role during ripening and of the factor affecting tyramine production is fundamental to limit intoxication due to this amine

Growth, biogenic amine production and tyrDC transcription of Enterococcus faecalis in synthetic medium containing defined amino acid concentrations

AIMS: The tyraminogenic potential of the strains Enterococcus faecalis EF37 and ATCC 29212 was investigated in a synthetic medium containing defined amounts of tyrosine and phenylalanine at different temperatures. METHODS AND RESULTS: Enterococci growth and the production of biogenic amines (BA) were evaluated in relation to their pre-growth in medium containing tyrosine. Significant differences between the two strains were evidenced at metabolic level. Both the pre-adapted strains grew faster in all the tested conditions, independently of the presence of the precursor. Temperatures of 30 and 40\ub0C positively affected the growth parameters. The tyrosine decarboxylase (tyrDC) activity of the strain EF37 was positively affected by pre-adaptation, while ATCC 29212 showed a faster and higher tyramine accumulation with not-adapted cells. The expression analysis of the gene tyrDC confirmed the influence of the growth conditions on gene transcription. CONCLUSIONS: The small differences found between the two strains in the maximum transcript level reached rapidly after the inoculum and the different behaviour in the tyramine accumulation suggested the possible involvement of complex regulation mechanisms on the tyrDC or on the membrane transport systems, which could affect the different BA accumulation trend. SIGNIFICANCE AND IMPACT OF THE STUDY: This study gives deeper insight into the metabolic regulation of tyrDC activity of enterococci

Foglio 026 Appiano - Guida ai percorsi Geologici

La pubblicazione delle carte geologiche dell'Alto Adige in scala 1:25.000 da parte dell'Amministrazione provinciale ha come scopo quello di fornire una moderna cartografia estesa a tutto il territorio provinciale in cui sia possibile trovare le pi\uf9 aggiornate conoscenze geologiche. In questo modo esse possono rappresentare un valido supporto per altri tipi di ricerche ed applicazioni ed un indispensabile strumento di base per la pianificazione territoriale ed urbanistica. Per consentire a tutti i fruitori della cartografia geologica di vedere e toccare con mano gli oggetti descritti, \ue8 nata l'idea di accompargare le carte geologiche a scala 1:25.000 con una "Guida geologica" in cui sono illustrati alcuni itinerari particolarmente rappresentativi ed interessanti, nonch\ue8 belli anche dal punto di vista geoturistico. La "Guida" si rivolge, oltre ai geologi (comprese le universit\ue0 che spesso utilizzano il nostro territorio per escursioni con studenti), a tutti gli appassionati della montagna e della natura in generale, sia residenti sia turisti. Il linguaggio usato e l'impostazione con approfondimenti per gradi speriamo consenta un'agevole fruizione sia agli esperti, sia agli appassionati

Control of tyramine and histamine accumulation by lactic acid bacteria using bacteriocin forming lactococci

The aim of this study was to evaluate the competitive effects of three bacteriocin producing strains of L. lactis subsp. lactis against two aminobiogenic lactic acid bacteria, i.e. the tyramine producing strain Enterococcus faecalis EF37 and the histamine producing strain Streptococcus thermophilus PRI60, inoculated at different initial concentration (from 2 to 6 log cfu/ml). The results showed that the three L. lactis subsp. lactis strains were able to produce bacteriocins: in particular, L. lactis subsp. lactis VR84 and EG46 produced, respectively, nisin Z and lacticin 481, while for the strains CG27 the bacteriocin has not been yet identified, even if its peptidic nature has been demonstrated. The co-culture of E. faecalis EF37 in combination with lactococci significantly reduced the growth potential of this aminobiogenic strain, both in terms of growth rate and maximum cell concentration, depending on the initial inoculum level of E. faecalis. Tyramine accumulation was strongly reduced when E. faecalis EF37 was inoculated at 2 log cfu/ml and, to a lesser extent, at 3 log cfu/ml, as a result of a lower cell load of the aminobiogenic strain. All the lactococci were more efficient in inhibiting streptococci in comparison with E. faecalis EF37; in particular, L. lactis subsp. lactis VR84 induced the death of S. thermophilus PRI60 and allowed the detection of histamine traces only at higher streptococci inoculum levels (5-6 log cfu/ml). The other two lactococcal strains did not show a lethal action against S. thermophilus PRI60, but were able to reduce its growth extent and histamine accumulation, even if L. lactis subsp. lactis EG46 was less effective when the initial streptococci concentration was 5 and 6 log cfu/ml. This preliminary study has clarified some aspects regarding the ratio between bacteriocinogenic strains and aminobiogenic strains with respect to the possibility to accumulate BA and has also showed that different bacteriocins can have different effects on BA production on the same strain. This knowledge is essentially aimed to use bacteriocinogenic lactococci as a predictable strategy against aminobiogenic bacteria present in cheese or other fermented foods

Control of tyramine and histamine accumulation by lactic acid bacteria using bacteriocin forming lactococci.

The aim of this study was to evaluate the competitive effects of three bacteriocin producing strains of Lactococcus lactis subsp. lactis against two aminobiogenic lactic acid bacteria, i.e. the tyramine producing strain Enterococcus faecalis EF37 and the histamine producing strain Streptococcus thermophilus PRI60, inoculated at different initial concentrations (from 2 to 6. log. cfu/ml). The results showed that the three L. lactis subsp. lactis strains were able to produce bacteriocins: in particular, L. lactis subsp. lactis VR84 and EG46 produced, respectively, nisin Z and lacticin 481, while for the strains CG27 the bacteriocin has not been yet identified, even if its peptidic nature has been demonstrated. The co-culture of E. faecalis EF37 in combination with lactococci significantly reduced the growth potential of this aminobiogenic strain, both in terms of growth rate and maximum cell concentration, depending on the initial inoculum level of E. faecalis. Tyramine accumulation was strongly reduced when E. faecalis EF37 was inoculated at 2. log. cfu/ml and, to a lesser extent, at 3. log. cfu/ml, as a result of a lower cell load of the aminobiogenic strain. All the lactococci were more efficient in inhibiting streptococci in comparison with E. faecalis EF37; in particular, L. lactis subsp. lactis VR84 induced the death of S. thermophilus PRI60 and allowed the detection of histamine traces only at higher streptococci inoculum levels (5-6. log. cfu/ml). The other two lactococcal strains did not show a lethal action against S. thermophilus PRI60, but were able to reduce its growth extent and histamine accumulation, even if L. lactis subsp. lactis EG46 was less effective when the initial streptococci concentration was 5 and 6. log. cfu/ml. This preliminary study has clarified some aspects regarding the ratio between bacteriocinogenic strains and aminobiogenic strains with respect to the possibility to accumulate BA and has also showed that different bacteriocins can have different effects on BA production on the same strain. This knowledge is essentially aimed to use bacteriocinogenic lactococci as a predictable strategy against aminobiogenic bacteria present in cheese or other fermented foods