Optimization of microwave-assisted extraction of ergosterol from Agaricus bisporus L. by-products using response surface methodology

This work intends to valorise by-products of the industrial processing of mushrooms to obtain ergosterol as a value-added compound. Agaricus bisporus L. is the world’s most consumed mushroom and one of the richest sources of ergosterol. Microwave-assisted extraction was used to replace conventional techniques that are time-consuming and need large amounts of solvent. Time (3-20 min), temperature (60-210 ºC) and solid-liquid ratio (1-20 g/L) were found the relevant variables to analyze the extraction process. To maximize the ergosterol extraction yield, response surface methodology was used to optimize the process. The global optimal extraction conditions were determined and comprise: 19.4±2.9 min, 132.8±12.4 ºC and 1.6±0.5 g/L, yielding 556.1±26.2 mg of ergosterol per 100 g of mushroom by-products. In the MAE optimal conditions, it was possible to obtain ergosterol in a similar value to the one obtained in other works when using the Soxhlet extraction method with a significant decrease in the time of extraction. The results show the potential of using the by-products of an agroindustry, mushrooms processing industry, as productive sources of ergosterol.The authors acknowledge FCT (Portugal) for financial support to CIMO (PEst-OE/AGUI/0690/2014), Sandrina A. Heleno (SFRH/BPD/101413/2014) and L. Barros (SFRH/BPD/107855/2015), to FCT/MEC and FEDER under Programme PT2020 for financial support to LSRE (Project UID/EQU/50020/2013), and to QREN, ON2 and FEDER (Projects NORTE-07-0124-FEDER-000014 and NORTE-07-0162-FEDER-000050). The authors also acknowledge Xunta de Galicia for financial support of the post-doctoral researcher M.A. Prieto, and to Patrícia Diz for some support in MAE experiments

Analysis of initial stabilization of cell efficiency in amorphous silicon photovoltaic modules under real outdoor conditions

[EN] This contribution presents a field study in which the initial stabilization of thin-film amorphous silicon (a-Si:H) is investigated. Two grid-connected a-Si:H photovoltaic plants have been monitored and analyzed under real outdoor conditions. A per-unit approach is proposed to compare PV plants with differences in their electrical characteristic and the start-up date. The representation of a normalized per unit PV power versus the accumulated incoming irradiation reveals an evolution that can be characterized through an exposure-response function. By this function, two populations of defects in the cells are detected. It is found that the stabilization process in the first year of operation produces a decrease of 10% in the peak power, equivalent to a decrease of 0.5% in cell efficiency. The use of the accumulated PSH for conducting the analysis of the initial stabilization produces similarities that cannot be obtained if a time scale is used. These results provide a powerful tool for PV plant designers because they enable a prediction to be made of the time-scale stabilization response in terms of unitary power, correlated with the peak sun hours received. (C) 2017 Elsevier Ltd. All rights reserved.This work was supported by Generalitat Valenciana (PROM-ETEOII/2014/059) and Spanish MINECO (Ministry of Economy and Competitiveness TEC2014-53727-C2-1-R).Mateo-Guerrero, C.; Hernández Fenollosa, MDLÁ.; Montero Reguera, ÁE.; Segui-Chilet, S. (2018). Analysis of initial stabilization of cell efficiency in amorphous silicon photovoltaic modules under real outdoor conditions. Renewable Energy. 120:114-125. https://doi.org/10.1016/j.renene.2017.12.054S11412512

Proposal for a simple and sensitive haemolytic assay for palytoxin: Toxicological dynamics, kinetics, ouabain inhibition and thermal stability

Benthic dinoflagellates of the genus Ostreopsis are important components of subtropical and tropical marine coral reef–lagoonal environments. Currently, as a result of global warming and trade globalization, they are also distributed worldwide. These microalgae are shown to produce palytoxin, one of the most potent non-protein marine toxins known. The haemolytic assay is a very easy, rapid and sensitive method to determine palytoxin. However, under the conditions reported in previous works this assay is inadequate for a rigorous dose–response treatment, since: (1) it produces degenerate sigmoidal profiles, with a pronounced slope which makes the calculation of the ED50 very sensitive to the experimental error; (2) at the usual work temperature, the in vitro stability of the system is low, which accentuates the variability and ambiguity of the response. To resolve these problems haemolysis of sheep erythrocytes is studied, including it's toxicological dynamics, kinetics, inhibition by ouabain and response to temperature. The results show that, to obtain a smoother, more stable and reproducible response, it is necessary to apply two resources simultaneously: operation at a moderate temperature and partial inhibition of the palytoxin by ouabain. It also produces highly reliable parameters and allows strict equivalencies to be established with the mouse bioassays, a traditional reference point, though bioethically questionable and 20 times less sensitive than the bioassay proposed here.Versión del editor3,083

Solid state fermentation for the production of lipolytic fungal enzymes

The production of lypolitic moulds in solid state fermentation was studied. Aspergillus oryzae and Rhizopus oryzae were grown on rice hulls using different media. Tween 80 and olive oil were employed as main carbon sources; the whole solid cultures were lyophilised and employed in heptane for catalysing the formation of various geranyl esters with molar conversions ranging from 40 to 95%, under optimised conditions, starting from 50 mM geraniol and equimolar amount of the acid

Mouse bioassay for palytoxin. Specific symptoms and dose-response against dose–death time relationships

Nowadays, a variety of protocols are applied to quantitate palytoxin. However, there is not desirable agreement among them, the confidence intervals of the basic toxicological parameters are too wide and the formal descriptions lack the necessary generality to establish comparisons. Currently, the mouse bioassay is the most accepted one to categorize marine toxins and it must constitute the reference for other methods. In the present work, the mouse bioassay for palytoxin is deeply analyzed and carefully described showing the initial symptoms of injected mice which are presented here in the first time. These symptoms clearly differ from the more common marine toxins described up to now. Regarding to the toxicological aspects two considerations are taking into account: (i) the empiric models based in the dose–death time relationships cause serious ambiguities and (ii) the traditional moving average method contains in its regular use any inaccuracy elements. Herein is demonstrated that the logistic equation and the accumulative function of Weibull’s distribution (with the modifications proposed) generate satisfactory toxicological descriptions in all the respects.Versión del edito