Photoionization in the time and frequency domain Isinger, M.; Squibb, R. J.; Busto, D. ...
Science (American Association for the Advancement of Science),
11/2017, Letnik:
358, Številka:
6365
Journal Article
Recenzirano
Odprti dostop
Ultrafast processes in matter, such as the electron emission after light absorption, can now be studied using ultrashort light pulses of attosecond duration (10−18 seconds) in the extreme ultraviolet ...spectral range. The lack of spectral resolution due to the use of short light pulses has raised issues in the interpretation of the experimental results and the comparison with theoretical calculations. We determine photoionization time delays in neon atoms over a 40–electron volt energy range with an interferometric technique combining high temporal and spectral resolution. We spectrally disentangle direct ionization from ionization with shake-up, in which a second electron is left in an excited state, and obtain excellent agreement with theoretical calculations, thereby solving a puzzle raised by 7-year-old measurements.
•Solvent-free glycerolysis catalyzed by Lipase PS-DI produces MAG rich in PUFA.•For the first time, oxidative stability is considered during glycerolysis design.•Simultaneous optimization of MAG ...yield and oxidative stability in glycerolysis design.•Optimized glycerolysis conditions improved end-product oxidative stability by 68%.
The production of mono- and diacylglycerols rich in polyunsaturated fatty acids is achieved in this study, by solvent-free glycerolysis of anchovy oil with lipase PS-DI from Burkholderia cepacia. Attention is focused on the oxidative stability of the reaction products, determined in terms of induction time (It). The effects of glycerol/triacylglycerol molar ratio, enzyme concentration, and reaction temperature on mono- and diacylglycerol production and It are all assessed. The operating conditions that optimized monoacylglycerol yields and oxidative stability were a glycerol/triacylglycerol ratio of 3/1, 9.0% (w/w) Lipase PS-DI, a stirring rate of 200 rpm, and a reaction time of 4 h, at 45.8 °C, producing a content of 24.8% and 51.9% of mono- and diacylglycerols, respectively, over an It of 1.41 h. The glycerolysis conditions determined by simultaneous optimization strategy increased the oxidative stability of the glycerolysis products by 68%, which rose from 0.84 h (individual optimization) to 1.41 h.
Virgin olive oil (VOO), characterized by its unique aroma, flavor, and health benefits, is subject to adulteration with the addition of oils obtained from other edible species. The consumption of ...adulterated olive oil with nut species, such as hazelnut or almond, leads to health and safety issues for consumers, due to their high allergenic potential. To detect almond and hazelnut in olive oil, several amplification systems have been analyzed by qPCR assay with a SYBR Green post-PCR melting curve analysis. The systems selected were Cora1F2/R2 and Madl, targeting the genes coding the allergenic protein
(hazelnut) and
(almond), respectively. These primers revealed adequate specificity for each of the targeted species. In addition, the result obtained demonstrated that this methodology can be used to detect olive oil adulteration with up to 5% of hazelnut or almond oil by a single qPCR assay, and with a level as low as 2.5% by a nested-qPCR assay. Thus, the present research has shown that the SYBR-based qPCR assay can be a rapid, precise, and accurate method to detect adulteration in olive oil.
The behavior against temperature and thermal stability of enzymes is a topic of importance for industrial biocatalysis. This study focuses on the kinetics and thermodynamics of the thermal ...inactivation of Lipase PS from B. cepacia and Palatase from R. miehei. Thermal inactivation was investigated using eight inactivation models at a temperature range of 40–70 °C. Kinetic modeling showed that the first-order model and Weibull distribution were the best equations to describe the residual activity of Lipase PS and Palatase, respectively. The results obtained from the kinetic parameters, decimal reduction time (D and tR), and temperature required (z and z’) indicated a higher thermal stability of Lipase PS compared to Palatase. The activation energy values (Ea) also indicated that higher energy was required to denature bacterial (34.8 kJ mol−1) than fungal (23.3 kJ mol−1) lipase. The thermodynamic inactivation parameters, Gibbs free energy (ΔG#), entropy (ΔS#), and enthalpy (ΔH#) were also determined. The results showed a ΔG# for Palatase (86.0–92.1 kJ mol−1) lower than for Lipase PS (98.6–104.9 kJ mol−1), and a negative entropic and positive enthalpic contribution for both lipases. A comparative molecular dynamics simulation and structural analysis at 40 °C and 70 °C were also performed.
•Olive oil authentication by qPCR depends on primer design and DNA amplificability.•Four olive-specific qPCR systems, based on trnL, are designed and validated.•The D-trnL system is selected on ...account of its high specificity and sensitivity.•DNA from different categories of olive oils was detected by the D-trnL system.•The design of the D-trnL system is suitable for olive oil authentication.
The applicability of qPCR in olive-oil authentication depends on the DNA obtained from the oils and the amplification primers. Therefore, four olive-specific amplification systems based on the trnL gene were designed (A-, B-, C- and D-trnL systems). The qPCR conditions, primer concentration and annealing temperature, were optimized. The systems were tested for efficiency and sensitivity to select the most suitable for olive oil authentication. The selected system (D-trnL) demonstrated specificity toward olive in contrast to other oleaginous species (canola, soybean, sunflower, maize, peanut and coconut) and showed high sensitivity in a broad linear dynamic range (LOD and LOQ: 500ng – 0.0625pg). This qPCR system enabled detection, with high sensitivity and specificity, of olive DNA isolated from oils processed in different ways, establishing it as an efficient method for the authentication of olive oil regardless of its category.
A new spectrophotometric end-point method to evaluate lipase activity in aqueous media is described. This procedure is based on blocking the enzyme reaction by adding chloroform:isoamyl alcohol ...(24:1) as a denaturating agent, and removing the precipitate by centrifugation. Emulsifier screening showed that the chemical component with the least effect on lipase activity from Thermomyces lanuginosus, Mucor javanicus, Aspergillus niger, Rhizomucor miehei, Penicillium camemberti and Burkholderia cepacia, in the proposed method, was 0.1% (w/w) gum arabic. In contrast, Triton X-100, SDS, sodium cholate and Tween 80 reduced lipase activity, depending on the microbial source of the latter. A comparative study with other end-point methods based on the addition of chemical reagents (NaOH, Na2CO3, THAM or acetone–ethanol) or in thermal treatments (chilling or heating) was performed. The proposed procedure was shown to be more accurate in comparison with other methods that were tested. Furthermore, the effectiveness of the method was demonstrated in a study of the specificity of six commercial lipases toward p-nitrophenyl decanoate (C10) and p-nitrophenyl palmitate (C16). The study also analyzed the kinetic behavior and catalytic efficiency of lipase from T. lanuginosus and B. cepacia toward p-nitrophenyl decanoate and p-nitrophenyl palmitate.
•A new spectrophotometric end-point method to evaluate lipase activity is developed.•The method is based on removing the enzyme after denaturating with Marmur solution.•This procedure is more effective and accurate that others described in literature.•The assay provides a simple way to screen the specificity and efficiency of lipases.
•High-quality DNA is essential for DNA-based food safety and traceability methods.•A CTAB-based method was optimized and amplifiable DNA yield was improved.•qPCR was used in the development and ...optimization of a DNA extraction method.•A rapid and economic DNA extraction method was successfully developed.•The method applicability was assayed in commercial vegetable oils and margarines.
This study describes the design of a suitable DNA isolation method from commercial vegetable oils for the application of DNA markers for food safety and traceability. Firstly, a comparative study was made of eight methods for the recovery of high quality DNA from olive, sunflower and palm oils, and a CTAB-based method was selected. In order to optimize this method, the effect of the organic compounds and several components in the lysis buffer and the lysis and precipitation time were evaluated. For the purpose of overcoming the limitations detected in spectrophotometric and PCR DNA yield evaluations, the performance of the extraction protocols during the optimization processes was evaluated using qPCR. The suggested DNA extraction optimized is less time consuming than other conventional DNA extraction methods, uses a reduced oil volume and is cheaper than available commercial kits. Additionally, the applicability of this method has been successfully assayed in ten commercial vegetable oils and derivatives.
Debittering of citrus by-products is required to obtain value-added compounds for application in the food industry (e.g., dietary fiber, bioactive compounds). In this work, the immobilization of
...Rhodococcus fascians
cells by encapsulation in Ca-alginate hollow beads and entrapment in poly(vinyl alcohol)/polyethylene glycol (PVA/PEG) cryogels was studied as an alternative to chemical treatments for degrading the bitter compound limonin. Previously, the
Rhodococcus
strain was adapted using orange peel extract to increase its tolerance to limonoids. The optimal conditions for the encapsulation of microbial cells were 2% Na-alginate, 4% CaCl
2
, 4% carboxymethylcellulose (CMC), and a microbial load of 0.6 OD
600
(optical density at 600 nm). For immobilization by entrapment, the optimal conditions were 8% PVA, 8% PEG, and 0.6 OD
600
microbial load. Immobilization by entrapment protected microbial cells better than encapsulation against the citrus medium stress conditions (acid pH and composition). Thus, under optimal immobilization conditions, limonin degradation was 32 and 28% for immobilization in PVA/PEG gels and in hollow beads, respectively, in synthetic juice (pH 3) after 72 h at 25 °C. Finally, the microbial cells entrapped in the cryogels showed a higher operational stability in orange juice than the encapsulated cells, with four consecutive cycles of reuse (runs of 24 h at 25 °C).
Key points
•
Increased tolerance to limonoids by adapting R. fascians with citrus by-products.
•
Entrapment provided cells with favorable microenvironment for debittering at acid pH.
•
Cryogel-immobilized cells showed the highest limonin degradation in citrus products.
BACKGROUND: This study was designed to evaluate and compare antioxidant capacity and radical scavenging activity of naringin and its aglycone by different in vitro assays. The effects of flavanones ...on lipid peroxidation, glutathione (GSH) oxidation and DNA cleavage were also assessed.RESULTS: The results showed that naringenin exhibited higher antioxidant capacity and hydroxyl and superoxide radical scavenger efficiency than naringin. Our results evidenced that glycosylation attenuated the efficiency in inhibiting the enzyme xanthine oxidase and the aglycone could act like a more active chelator of metallic ions than the glycoside. Additionally, naringenin showed a greater effectiveness in the protection against oxidative damage to lipids in a dose-dependent manner. Both flavanones were equally effective in reducing DNA damage. However, they show no protective effect on oxidation of GSH.CONCLUSION: The data obtained support the importance of characterizing the ratio naringin/naringenin in foods when they are evaluated for their health benefits.
Neutrase, a commercial preparation of Bacillus subtilis, was covalently immobilized on alginate−glutaraldehyde beads. Immobilization conditions and characterization of the immobilized enzyme were ...investigated. Central composite design and response surface methods were employed to evaluate the effects of immobilization parameters, such as glutaraldehyde concentration, enzyme loading, immobilization pH, and immobilization time. Under optimized working conditions (2% alginate, 6.2% glutaraldehyde, 61.84 U mL−1 Neutrase, pH 6.2, and 60 min) the immobilization yield was about 50%. The immobilized enzyme exhibited higher K m compared to the soluble enzyme. The pH−activity profile was widened upon immobilization. The optimum temperature was shifted from 50 to 60 °C, and the apparent activation energy was decreased from 47.7 to 22.0 kJ mol−1 by immobilization. The immobilized enzyme also showed significantly enhanced thermal stability.
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