Phosphorus doped cyanobacterial biochar catalyzes efficient persulfate oxidation of the antibiotic norfloxacin.

In this study, cyanobacterial biochars (CBs) enriched/doped with non-metallic elements were prepared by pyrolysis of biomass amended with different N, S, and P containing compounds. Their catalytic reactivity was tested for persulfate oxidation of the antibiotic norfloxacin (NOR). N and S doping failed to improve CB catalytic reactivity, while P doping increased reactivity 5 times compared with un-doped biochar. Biochars produced with organic phosphorus dopants showed the highest reactivity. Post-acid-washing improved catalytic reactivity. In particular, 950 ℃ acid-washed triphenyl-phosphate doped CB showed the largest degradation rate and reached 79% NOR mineralization in 2 h. Main attributes for P-doped CBs high reactivity were large specific surface areas (up to 655 m2/g), high adsorption, high C-P-O content, graphitic P and non-radical degradation pathway (electron transfer). This study demonstrates a new way to reuse waste biomass by producing efficient P-doped metal-free biochars and presents a basic framework for designing carbon-based catalysts for organic pollutant degradation.

Fast peroxydisulfate oxidation of the antibiotic norfloxacin catalyzed by cyanobacterial biochar.

Peroxydisulfate (PDS) is a common oxidant for organic contaminant remediation. PDS is typically activated by metal catalysts to generate reactive radicals. Unfortunately, as radicals are non-selective and metal catalysts may cause secondary contamination, alternative selective non-radical pathways and non-metal catalysts need attention. Here we investigated PDS oxidation of commonly detected antibiotic Norfloxacin (NOR) using cyanobacterial nitrogen rich biochars (CBs) as catalysts. NOR was fully degraded by CB pyrolysed at 950 °C (CB950) within 120 min. CB950 caused threefold faster degradation than low pyrolysis temperature (PT) CBs and achieved a maximum surface area normalized rate constant of 4.38 × 10-2 min-1 m-2 L compared to widely used metal catalysts. CB950 maintained full reactivity after four repeated uses. High defluorination (82%) and mineralization (>82%) were observed for CB950/PDS. CBs were active over a broad pH range (3-10), but with twice as high rates under alkaline compared with neutral conditions. NOR is degraded by organic, •OH and SO4•- radicals in low PT CBs/PDS systems, where the presence of MnII promotes radical generation. Electron transfer reactions with radicals supplemented dominate high PT CBs/PDS systems. This study demonstrates high PT biochars from algal bloom biomass may find use as catalysts for organic contaminant oxidation.

Effect of dry hopping on the oxidative stability of beer.

Electron spin resonance (ESR) spectroscopy was used todeterminethe effect of dry hopping on the oxidative stability and antioxidative potential of beer.Commercial beerwasdry-hopped at 5 °C and 20 °Cwith six hop varieties (Polish and American). The rate of radical formation and lag time were found to depend on the variety of hop used. An increase in the lag time and a decrease in the rate of radical formation occurred when dry-hopping was performed at 20 °C for all hop varieties (at 5 °C in some varieties). The lag time had a strong correlation with the TPC (total polyphenols content) in beer. The rate of radical formation was correlated with the iron content of the beer. A decrease in iron concentration was observed after dry-hopping at 20 °C. Overall, the evaluation of free radical formation using ESR is useful for predicting oxidative changes in beer during storage.

Wheat Gluten Peptides Enhance Ethanol Stress Tolerance by Regulating the Membrane Lipid Composition in Yeast.

Wheat gluten peptides (WGPs), identified as Leu-Leu (LL), Leu-Leu-Leu (LLL), and Leu-Met-Leu (LML), were tested for their impacts on cell growth, membrane lipid composition, and membrane homeostasis of yeast under ethanol stress. The results showed that WGP supplementation could strengthen cell growth and viability and enhance the ethanol stress tolerance of yeast. WGP supplementation increased the expressions of OLE1 and ERG1 and enhanced the levels of oleic acid (C18:1) and ergosterol in yeast cell membranes. Moreover, LLL and LML exhibited a better protective effect for yeast under ethanol stress compared to LL. LLL and LML supplementation led to 20.3 ± 1.5% and 18.9 ± 1.7% enhancement in cell membrane fluidity, 21.8 ± 1.6% and 30.5 ± 1.1% increase in membrane integrity, and 26.3 ± 4.8% and 27.6 ± 4.6% decrease in membrane permeability in yeast under ethanol stress, respectively. The results from scanning electron microscopy (SEM) elucidated that WGP supplementation is favorable for the maintenance of yeast cell morphology under ethanol stress. All of these results revealed that WGP is an efficient enhancer for improving the ethanol stress tolerance of yeast by regulating the membrane lipid composition.

Modulation of gastrointestinal digestion of ß-lactoglobulin and micellar casein following binding by (-)-epigallocatechin-3-gallate (EGCG) and green tea flavanols.

The effect of binding of flavonoids, (-)-epigallocatechin-3-gallate (EGCG) and green tea extract (GTE), to beta-lactoglobulin (ß-Lg) and micellar casein (micellar casein isolate, MCI) on protein digestibility was investigated. ß-Lg resisted digestion by pepsin, but in the presence of EGCG the digestion of ß-Lg was enhanced. Binding of EGCG to ß-Lg was identified by nitro blue tetrazolium (NBT) staining and found, by isothermal titration calorimetry, to be an enthalpy-driven exothermic process, with a binding constant of 19 950 L mol-1. Binding promoted a more rapid digestion of ß-Lg during simulated upper duodenal digestion. NBT staining indicated a loss of binding of EGCG to ß-Lg during combined gastric and distal small intestinal digestion and correlated with the cleavage of ß-Lg. However, increased ß-Lg heteromer formation and reduced ß-Lg monomer digestibility were observed for the ß-Lg-GTE complex. MCI was more digestible than ß-Lg during pepsin digestion, but reduced digestibility was observed for both MCI-EGCG and MCI-GTE complexes, with loss of binding during intestinal digestion. The free radical scavenging capacity (FRSC) of EGCG remained stable for the ß-Lg-EGCG complex throughout the gastric and intestinal phases of digestion, but this was significantly lowered for the MCI-EGCG complex. These results indicated that polyphenols bind to milk proteins modulating the in vitro digestibility and FRSC of ß-Lg and MCI as a result of the formation of complexes.

Morphology and Structure of Solid Lipid Nanoparticles Loaded with High Concentrations of ß-Carotene.

Solid lipid nanoparticles (SLNs) containing up to 37.5 wt % all-trans ß-carotene in the lipid phase are potential water-dispersible food colorants. SLNs have been made by hot-melt high-pressure homogenization with fully hydrogenated sunflower oil and with polysorbate 80 and sunflower lecithin as stabilizers. Atomic force microscopy revealed the SLNs had thin platelet structures most likely derived from the triglyceride crystal ß-form, as detected by X-ray diffraction. No indications of crystalline ß-carotene were detected. High-performance liquid chromatography analysis showed the extensive isomerization of ß-carotene into more than 10 cis isomers, suggesting that it is present as an amorphous mixture. The high ß-carotene loadings did not affect the triglyceride crystal structure and the morphology of the SLNs. It is suggested the SLNs consist of a platelet core of crystalline triglyceride surrounded by an amorphous ß-carotene-containing layer. The layered structure is suggested to affect the coloring power of the SLNs at ß-carotene loadings above 15 wt % of the lipid phase.

Interactions of dietary fiber bound antioxidants with hydroxycinnamic and hydroxybenzoic acids in aqueous and liposome media.

The interactions between dietary fiber (DF)-bound antioxidants and free antioxidants, with different substitution patterns of -OH and -OCH3 groups on their aromatic rings has been investigated. The activity and efficiency of these interactions were examined with a structural approach. Whole wheat (WW) DF-bound antioxidants and 21 hydroxycinnamic acid/hydroxybenzoic acids (HCA/HBA) were used in the experimental studies. Studies were performed in liposome and aqueous media by monitoring lipid oxidation and scavenging of DPPH radical in the presence of WW-bound antioxidants and HCA/HBA derivatives. Predominantly synergistic interactions were observed in aqueous medium, while both synergistic and antagonistic interactions were seen in liposome medium. Concentrations of HCA/HBA and WW-bound antioxidants in mixtures and their 2-way interactions made significant effect on lipid oxidation and radical scavenging reactions, with some exceptions. HCA/HBA derivatives with 3 ,4 -dihydroxyphenyl substitution acted as strong antioxidants in liposome medium, while the number of -OH groups affected antioxidant activity in aqueous medium.

Influence of mediators on laccase catalyzed radical formation in lignin.

Laccases (EC 1.10.3.2) catalyze oxidation of phenolic groups in lignin to phenoxyl radicals during reduction of O2 to H2O. Here, we examine the influence on this radical formation of mediators which are presumed to act by shuttling electrons between the laccase and the subunits in lignin that the enzyme cannot approach directly. Treatments of three different lignins with laccase-mediator-systems (LMS) including laccases derived from Trametes versicolor and Myceliophthora thermophila, respectively, and four individual mediators, 1-hydroxybenzotriazole (HBT), N-hydroxyphthalimide (HPI), 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were assessed by real time electron paramagnetic resonance measurements. Radical steady state concentrations and radical formation rates were quantified. LMS treatments with 500 µM N-OH type mediators (HPI or HBT) did not affect the lignin radical formation, but increased doses of those mediators (5 mM) surprisingly led to significantly decreased radical formation rates and lowered steady state radical concentrations. Laccase-TEMPO treatment at a 5 mM mediator dose was the only system that significantly increased steady state radical concentration and rate of radical formation in beech organosolv lignin. The data suggest that electron shuttling by mediators is not a significant general mechanism for enhancing laccase catalyzed oxidation of biorefinery lignin substrates, and the results thus provide a new view on laccase catalyzed lignin modification.

Interactions of coffee and bread crust melanoidins with hydroxycinnamic and hydroxybenzoic acids in aqueous radical environment.

The interactions of coffee and bread crust melanoidins with hydroxycinnamic and hydroxybenzoic acids (HCA/HBA) containing different numbers of -OH and -OCH3 groups localized at different positions on the aromatic ring were investigated. By doing so, mechanism of the interactions was intended to be explained with a structural approach. Experimental studies were carried out in DPPH radical medium. Chemometric methods were used for experimental design and multivariate data analysis. Area under the curve (AUC) values calculated from the plots of time versus inhibition (%) for coffee and bread crust melanoidins and HCA/HBA derivatives were ranged between 6532 ±â€¯97-19,106 ±â€¯85, 3997 ±â€¯102-7565 ±â€¯159 and - 1678 ±â€¯81-22,486 ±â€¯119, respectively. Synergistic interactions were revealed for both coffee and bread crust melanoidins and HCA/HBA derivatives. The significance of the concentrations of coffee and bread crust melanoidins on radical scavenging activity was clearly centered from the scores plots obtained via Principal component analysis (PCA). Phases of radical scavenging reactions were also revealed from the loadings plots.

Direct rate assessment of laccase catalysed radical formation in lignin by electron paramagnetic resonance spectroscopy.

Laccases (EC 1.10.3.2) catalyse removal of an electron and a proton from phenolic hydroxyl groups, including phenolic hydroxyls in lignins, to form phenoxy radicals during reduction of O2. We employed electron paramagnetic resonance spectroscopy (EPR) for real time measurement of such catalytic radical formation activity on three types of lignin (two types of organosolv lignin, and a lignin rich residue from wheat straw hydrolysis) brought about by two different fungal laccases, derived from Trametes versicolor (Tv) and Myceliophthora thermophila (Mt), respectively. Laccase addition to suspensions of the individual lignin samples produced immediate time and enzyme dose dependent increases in intensity in the EPR signal with g-values in the range 2.0047-2.0050 allowing a direct quantitative monitoring of the radical formation and thus allowed laccase enzyme kinetics assessment on lignin. The experimental data verified that the laccases acted upon the insoluble lignin substrates in the suspensions. When the action on the lignin substrates of the two laccases were compared on equal enzyme dosage levels (by activity units on syringaldazine) the Mt laccase exerted a significantly faster radical formation than the Tv laccase on all three types of lignin substrates. When comparing the equal laccase dose rates on the three lignin substrates the enzymatic radical formation rate on the wheat straw lignin residue was consistently higher than those of the organosolv lignins. The pH-temperature optimum for the radical formation rate in organosolv lignin was determined by response surface methodology to pH 4.8, 33°C and pH 5.8, 33°C for the Tv laccase and the Mt laccase, respectively. The results verify direct radical formation action of fungal laccases on lignin without addition of mediators and the EPR methodology provides a new type of enzyme assay of laccases on lignin.

A role for taurine in mitochondrial function.

The mitochondrial pH gradient across the inner-membrane is stabilised by buffering of the matrix. A low-molecular mass buffer compound has to be localised in the matrix to maintain its alkaline pH value. Taurine is found ubiquitously in animal cells with concentrations in the millimolar range and its pKa value is determined to 9.0 (25 degrees C) and 8.6 (37 degrees C), respectively. Localisation of such a low-molecular buffer in the mitochondrial matrix, transforms the matrix into a biochemical reaction chamber for the important matrix-localised enzyme systems. Three acyl-CoA dehydrogenase enzymes, which are pivotal for beta-oxidation of fatty acids, are demonstrated to have optimal activity in a taurine buffer. By application of the model presented, taurine depletion caused by hyperglycemia could provide a link between mitochondrial dysfunction and diabetes.

The important role of taurine in oxidative metabolism.

Several studies have demonstrated that especially high taurine concentrations are found in tissues with high oxidative activity, whereas lower concentrations are found in tissues with primary glycolytic activity. Based on such observations, we have studied if taurine is involved in mitochondrial oxidation. Several pieces of information have demonstrated taurine localisation in the mitochondria. We have developed a general biochemical model with preliminary data demonstrating the important role of taurine as mitochondrial matrix buffer for stabilising the mitochondrial oxidation. The model can have far-reaching perspectives, e.g., explaining the often-suggested anti-oxidative role of taurine, in contrast to the fact that taurine is very difficult to chemically oxidise. By stabilising the environment in the mitochondria, taurine will prevent leakage of the reactive compounds formed in the reactive mitochondrial environment and thus indirectly act as an antioxidant. Consequently, the model represents a new concept for understanding mitochondrial dysfunction by emphasising the importance of taurine for providing sufficient pH buffering in the mitochondrial matrix.