Pesticide residue levels in strawberry processing by-products that are rich in ellagitannins and an assessment of their dietary risk to consumers

Background: According to many scientific studies, ellagitannins are beneficial for human health. One of the sources of these compounds is strawberry press-cake. This material can be used for the production of dietary fiber or ellagitannin preparations. The health safety of press cake and the preparations that are rich in ellagitannins obtained from it depend on pesticide residue levels, mainly fungicides, which are used for strawberry protection. Aim: The aim of the work was a dietary risk assessment measured by the %ADI (acceptable daily intake) and MOE (margin of exposure) associated with the presence of pesticide residues for the consumption of strawberry processing by-products containing an amount of ellagitannins equivalent to amount present in 100 g of fresh strawberries. In our study, we investigated the contents of pesticides that are approved for use against strawberry diseases and pests. Results: The total contents of pesticides in strawberry press-cake seeds (SPCS), exhausted strawberry flesh (ESF) and strawberry ellagitannin preparation (SEP) were 2143, 13,464 and 20,225 μg/kg, respectively. The analyzed products were dominated by fungicides as 96% of the total content of the tested pesticides. In the tested samples, we detected 11 fungicides and 3 insecticides. The dietary risk to consumer health, which depends on the presence of pesticide residues, in %ADI of daily consumption of ellagitannins (as dried extract (SEP), seeds (SPCS) or flesh (ESF)) ranged from 0.2% to 4.1% in a dose that was equivalent to 100 g of strawberries. Conclusion: Although the pesticide residue contents in strawberry by-products are higher than in fresh fruits, the suggested doses of the by-products are lower. Therefore, the dietary risk to consumers from strawberry by-products is comparable to that from fresh fruits

Soil fungi isolated from DDT-polluted soils: assessment of tolerance, interspecific metabolic diversity and efficacy of rhizo-bioremediation

DDT (dichloro-diphenyl-trichloroethane) was widely used worldwide to control agricultural pests and vectors of several insect-borne human diseases, but its use was banned in most industrialized countries since 1972 due to toxicological concerns. However, due to its persistence in the environment, residues still remain in environ-mental compartments becoming long-term sources of exposure affecting organisms. The metabolic and enzy-matic versatility of fungi can be exploited for DDT biodegradation purposes. We have selected two fungal strains (Trichoderma harzianum and Rhizopus stolonifer) from DDT-contaminated agricultural soils, to study their tolerance to high concentration of DDT and to evaluate fungal interspecific functional diversity and catabolic versatility at the presence of DDT, by using Phenotype MicroArray™ system. Both strains showed clear toler-ance to high DDT concentration. Fungi were able to use the most of available microplate substrates, resulting in both high metabolic versatility and relevant ecological functionality in the colonisation of new sub-strates/habitats. The phenotype profile highlighted both inibithion and stimulation of co-metabolic activities in the presence of this xenobiotic, suggesting the activation of specific metabolic responses to cope with chemical stress. Rhizo-bioremediation trials were also performed using Cucurbita pepo cv. Soraya plants. Both fungi in-creased the capacity of the plant to uptake DDT isomers and metabolites in roots. The increased uptake was reflected also in higher translocation to green-tissues of the plant which would ease removal of residues from polluted sites. The results showed that the fungal species studied might provide powerful insight into the po-tentiality of rhizo-bioremediation

Microbial biodegradation and phytoaccumulation as a possible strategy to reduce DDT pollution in soils of organic farms

W Instytucie Ogrodnictwa podjęto próbę połączenia: biodegradacji przez mikroorganizmy wspomagające rośliny wykazujące właściwości akumulujące w celu redukcji skażenia gleb przez pestycydy w uprawach ekologicznych. Stosowano wytypowane gatunki roślin i konsorcja mikroorganizmów (bakterie i grzyby mykoryzowe), korzystne dla rozwoju roślin, w celu zbadania możliwości pobierania DDT i jego metabolitów przez te rośliny. Ponadto z gleby zanieczyszczonej DDT izolowano rozwijające się w niej grzyby i bakterie, w celu identyfikacji szczepów zdolnych do metabolizowania tych związków. Badania takie są konieczne, gdyż z 53 prób gleby pobranych w ośmiu województwach w Polsce, aż 80% zawierało pozostałości tych substancji. Niektóre gatunki roślin (np. Cucurbita pepo) wykazały pewną zdolność pobierania i transportu związków DDT do części nadziemnych, ale nie do owoców. Zastosowane konsorcja mikroorganizmów dość efektywnie wspomagały, pobieranie w/w toksycznych substancji przez rośliny. Z gleb zanieczyszczonych związkami DDT wyizolowano i zidentyfikowano 179 szczepów należących do 59 gatunków grzybów saprotroficznych. Przeprowadzono testy tolerancji / oporu (Rt: Rc, T.I.) w obecności wysokiego stężenia DDT by ocenić i wytypować najlepsze szczepy wykazujące zdolności biodegradacji DDT.The study has been undertaken at the Research Institute of Horticulture to investigate microorganism biodegradation and phytoaccumulation of organic pesticides present in soils managed under organic farming methods. Consortia of microorganisms, such as plant beneficial bacteria and fungi (PGPR and mycorrhizal), were used in association to specific plant species to explore the possibility of breakdown DDT and its metabolites into harmless compounds or to foster their uptake by the plants. Furthermore, soil polluted with DDT were used to isolate fungi and bacteria that were able to thrive in them aiming at identifying strains able to metabolize these compounds. Such studies were prompted by the outcome of a survey of 53 soil samples gathered from eight Voivodships in Poland showing that 80% contained residues of this substances. Some plant species (e.g. Cucurbita pepo) showed some translocation capacity into above-soil organs, but not to physiological sinks such as fruits. The used microbial consortia fostered the uptake of DDT and its metabolites into the root system. 179 strains belonging to 59 saprotrophic soil fungal species were isolated and identified from polluted soils. Tolerance/resistance tests (Rt:Rc; T.I.) in presence of high DDT concentration were performed in order to select the best candidates for DDT biodegradation which hold promise for bioremediation purposes

Rhizo-bioremediation of DDT-contaminated soils

Developing an inexpensive, effective and environmentally-friendly method of remediation of persistent organic pollutants is still an emerging need. Exploiting natural rhizosphere microorganisms, having capacity to degrade various xenobiotics, in association to plants able to accumulate the pollutants into their biomass, is a promising alternative to conventional remediation techniques. In this respect, fungi can play a key role. Several reports are showing high potential of Cucurbitaceae in phytoremediation of DDT and its metabolites. In this study we present the results of rhizo-bioremediation of DDT using different varieties of Cucurbita pepo, inoculated in pot experiments with three fungal strains, isolated from DDT-contaminated soils in Poland, belonging to Trichoderma, Rhizopus and Mortierella genera. All the tested strains induced an increased uptake of DDT residues, either in case of “old” or recent contamination of the soil, in the C. pepo plants, thus reducing the content in the rhizospheric soil (about 50-60%) in comparison to control plants. The applied microfungi seemed also to influence the translocation of DDT from roots to the upper parts of the plant. Nevertheless, we did not detect DDT residues in the edible parts (fruit) of C. pepo. The proposed co-remediation strategy is discussed in view of possible interactions between plant genotypes and fungal strains that can affect the efficacy and/or mechanisms of this promising method of bioremediation. The work was supported by a grant of the Polish Ministry of Agriculture and Rural Development

Bioremediation of dichlorodiphenyltrichloroethane (DDT)-contaminated agricultural soils. Potential of two autochthonous saprotrophic fungal strains

DDT (dichlorodiphenyltrichloroethane) was used worldwide as an organochlorine insecticide to control agricultural pests and vectors of several insectborne human diseases. It was banned in most industrialized countries; however, due to its persistence in the environment, DDT residues remain in environmental compartments, becoming long-term sources of exposure. To identify and select fungal species suitable for bioremediation of DDT-contaminated sites, soil samples were collected from DDT-contaminated agricultural soils in Poland, and 38 fungal taxa among 18 genera were isolated. Two of them, Trichoderma hamatum FBL 587 and Rhizopus arrhizus FBL 578, were tested for tolerance in the presence of 1-mg liter-1 DDT concentration by using two indices based on fungal growth rate and biomass production (the tolerance indices Rt:Rc and TI), showing a clear tolerance to DDT. The two selected strains were studied to evaluate catabolic versatility on 95 carbon sources with or without DDT by using the Phenotype MicroArray system and to investigate the induced oxidative stress responses. The two strains were able to use most of the substrates provided, resulting in both high metabolic versatility and ecological functionality in the use of carbon sources, despite the presence of DDT. The activation of specific metabolic responses with species-dependent antioxidant enzymes to cope with the induced chemical stress has been hypothesized, since the presence of DDT promoted a higher formation of reactive oxygen species in fungal cells than the controls. The tested fungi represent attractive potential candidates for bioremediation of DDT-contaminated soil and are worthy of further investigations