Phytotoxicity and chelating capacity of spent coffee grounds: Two contrasting faces in its use as soil organic amendment.

Spent coffee grounds (SCG) are a bioresidue generated in large amounts worldwide, which could be employed as either fresh or transformed organic soil amendment, by means of different treatments in order to improve its agronomic qualities. An in vitro experiment was conducted in order to evaluate the effect of using different bioamendments derived from spent coffee grounds (SCG) on biomass and Zn, Cu and Fe content of lettuces. Application of 7.5% (w/w) fresh SCG, vermicompost, compost, biochars (at 270 and 400 °C; pyrolysis), SCG washed with ethanol and water, and hydrolysed SCG was carried out in an agricultural soil (Cambic Calcisol). In order to compare with conventional agriculture, the addition of NPK fertilizer was also assessed. Only vermicompost and biochar at 400 °C overcome the growth limitation of SCG. However, these treatments diminished Zn, Cu and Fe concentrations in lettuce probably due to the destruction (microbial degradation/thermal treatment) of natural chelating components (polyphenols). Increase in mineral content was observed in those treatments that did not completely eliminate polyphenols. NPK fertilizer gave rise to lettuces with higher biomass but lower micronutrients content. The results lead us to the possible solution for the use of SCG as organic amendment by vermicomposting and biocharization in order to eliminate toxicity.

Spent coffee grounds improve the nutritional value in elements of lettuce (Lactuca sativa L.) and are an ecological alternative to inorganic fertilizers.

The element concentration in lettuces grouped in 5 categories (baby variety, cultivated in agricultural soils with low or high percentages of spent coffee grounds-SCG, without SCG and with NPK) were measured. Lettuces cultivated in agricultural soils amended with SCG had significantly higher levels of several essential (V, Fe, Co, V, and probably Mn and Zn) and toxic elements (Al and probably As), without reaching their toxicological limits. Additionally, blocking of N uptake and therefore plant biomass, and probably Cd absorption from agricultural soil was observed. Organic farming with SCG ameliorates element concentrations in lettuces vs. NPK fertilization. The linear correlations among element uptake and the amendment of SCG could be related with their chelation by some SCG components, such as melanoidins and with the decrease in the soil pH. In conclusion, the addition of SCG produces lettuces with higher element content.

Relationship between HMF intake and SMF formation in vivo: An animal and human study.

SCOPE: 5-Hydroxymethylfurfural (HMF) is a furanic compound produced in heat-processed foods by nonenzymatic browning reactions. HMF has been demonstrated to be hepato- and nephrotoxic in animals with a link to its metabolite 5-sulfooxymethylfurfural (SMF). To date little is known about either the formation of SMF from ingested HMF or the formation of DNA adducts in animals or human beings. METHODS AND RESULTS: To assess SMF in vivo formation, we first performed a study in mice treated with high/low doses of oral HMF. We found increased concentrations of SMF in plasma and DNA SMF-adducts in leukocytes, hepatic tissue, and kidneys by means of LC-MS/MS, but no spatial formation in such tissues was observed by MALDI-MS imaging technology due to low sensitivity. In a second experiment, we measured the exposure to HMF in a Spanish preadolescent population. We analyzed the concentration of HMF metabolites (plasma, urine) and measured, for the first time, the presence of SMF in plasma and DNA SMF-adducts in leukocytes. CONCLUSION: This study provides the first evidence that oral HMF is readily transformed into SMF in vivo, giving rise to the formation of DNA adducts in a direct relation with HMF intake, both in animals and human beings.