Addition Of Sulfite Research Articles

Coumarin-based fluorescent probes for colorimetric and ratiometric fluorescent detection of sulfite: Structure-activity relationship

Six coumarin-based fluorescent probes were designed and synthesized for the detection of sulfite. The probes were constructed based on “fluorophore-receptor/linker-steric group” mode with N,N-diethyl-7-aminocoumarin (DEA) or 2,3,5,6-1H,4H-tetrahydro-quinolazino-(9,9a,1-gh)coumarin (THQ) as the fluorophore, 2-naphthyl ketone (N) or phenyl ketone (B) as the steric group and vinyl (1) or 1,3-butadienyl (2) as the receptor/linker. The effects of the fluorophore, the linker and the steric group on the photophysical properties and sensing performance were systematically studied. Among all the probes, DEA-N2 exhibited the most excellent spectral responses toward sulfite: upon addition of sulfite, the absorption and emission maxima shifted from 488 nm to 405 nm and–from 684 nm to 484 nm, respectively. I484/I688 displayed good linear relationship with sulfite concentration in the range of 3–50 μM, with a detection limit of 0.31 μM. The experimental results demonstrate that DEA-N2 has potential in ratiometric fluorescent imaging of mitochondrial sulfite in living cells.

Effects of pyrite, quartz and sodium sulfite on roasting of a refractory sulfide concentrate and gold, silver, copper leaching during cyanidation

The oxidation roasting pretreatment process, which is a mature and dominant industrial practice for treating complex polymetallic gold deposits, has a low recovery of associated silver and exhibits an unclear reaction sequence. This study takes a silver-containing gold ore as the research object and investigates the effect of (i) sodium sulfite as an additive, (ii) main gold-bearing mineral pyrite, and (iii) gangue mineral quartz, on silver during the roasting process in roasting and leaching tests. Characterization techniques included scanning electron microscopy–energy dispersive spectroscopy analysis, and thermogravimetry–differential scanning calorimetry analysis. The results based on thermodynamic calculations and characterization show that the main reason for the low extraction of silver is that the calcined product (i.e., iron silicate) formed by the reaction between pyrite and quartz during the roasting process is mutually absorbed and wrapped with silver oxide. In addition, silver minerals decompose some iron sulfides and iron oxides under high-temperature conditions, promoting the reaction of iron and quartz to form iron silicate while strengthening the secondary encapsulation of silver by products of roasting, thus deteriorating the extraction of silver. The addition of sodium sulfite reduces the formation of iron silicate and increases the extraction of silver by directly promoting the conversion of pyrite to iron oxide. This study provides a theoretical basis for further improving the roasting and leaching of silver.

Use of AirMixing M.I.® resonance waves to produce aroma richer Sangiovese wine without sulphites addition in a sustainable way

In recent years, wine without sulphite addition has grown increasingly popular. In this work, resonance waves (AirMixing M.I.®) were applied to Sangiovese must in fermentation to produce wine without sulphite addition, monitoring the fermentation kinetics and analyzing polyphenols and volatile organic compounds (VOCs) extraction. Resonance waves were created by injecting compressed air into a 10 hL stainless steel tank filled with Sangiovese must, without pumping-over/delestage, and no sulphites in all the process (AM). Control wine was produced using pumping-over/delestage and adding sulphur dioxide. After 4 months in bottles, simulating the commercial habit used to sell in spring the last year wine, volatile acidity was significantly lower in AM wine, while total anthocyanins, trans-resveratrol and free quercetin were significantly higher. Among free (VOCs), the classes of terpenes and benzenoids were significantly higher in the Control wine while the classes of aldehydes, alcohols, volatile phenols, lactones and pyrazine were in the AM wine. Unlike free VOCs, in glycosylated VOCs, terpenes and benzenoids were significantly higher in AM wine. In conclusion, resonance waves permit to speed up the fermentation increasing phenols extraction and producing wines with excellent maintenance of VOCs, requiring less energy and labor, and thus being more economically and environmentally sustainable.

Background-Free and Reversible Upconversion Hydrogel Sensing Platform for Visual Monitoring of Sulfite.

Excessive sulfite usage in food and pharmaceutical production causes respiratory and neurological diseases, underscoring the need for a sensitive and rapid quantification strategy. The portable sensing platform based on a luminescent hydrogel sensor is a powerful tool for the on-site, real-time detection of sulfite ions. However, the lack of recyclability in almost all reaction-based hydrogel sensors increases the application cost. This study constructed a reversible and upconversion nanoprobe combining upconversion nanoparticles (UCNPs) and pararosaniline (PAR) for sulfite detection. The upconversion nanoprobe was further encapsulated in a three-dimensional polyacrylamide hydrogel matrix to create a background-free, reversible hydrogel sensor. The near-infrared excitation of UCNPs avoids the autofluorescence in the hydrogel and real samples. Meanwhile, PAR serves as a specific recognition unit for sulfite ions. After the addition of sulfites, a specific reaction occurs between PAR and sulfites, leading to the recovery of characteristic emission at 540 nm, achieving sensitive detection of sulfite ions. Importantly, this specific reaction is reversible under thermal treatment, allowing the hydrogel sensor to return to its initial state and thus enabling reversible detection of sulfite ions. Furthermore, a portable sensing platform is developed to realize point-of-care, real-time quantitative detection of sulfite ions. The proposed upconversion reversible hydrogel sensor provides a new sensing strategy for the detection of hazardous substances in food and offers new insights into the preparation of reversible, highly sensitive hydrogel sensors.

Is it possible to produce canned champignon mushrooms with less sulfite?

This study aimed to evaluate the feasibility of reducing sulfite levels in canned mushrooms (Agaricus bisporus). Four formulations were developed: without sulfite and without condiment (F1); without sulfite but with condiment (F2); with sulfite but without condiment (F3); and with both sulfite and condiment (F4). The control group (C) consisted of traditional canned mushrooms prepared by the producer. These treatments were evaluated over a 42-day period. Acidity and pH analyses revealed that the control and F1 maintained a stable pH (<4.5) for 42 days. The formulations exhibited a greater browning index than fresh mushrooms at time zero. F3 demonstrated the smallest overall color difference (ΔE) between storage times 0 and day 42. A consumer study indicated that the addition of sulfite positively influenced the color of canned mushrooms in relation to purchase intention. However, when the influence of labeling was evaluated, sample F1, labeled as “absence of sulfite,” elicited greater purchase intention among consumers. Although consumers traditionally prefer pale yellow mushrooms, often obtained through sulfites, this study suggests the commercial viability of canned champignons with controlled sulfite content when coupled with appropriate marketing strategies.

Abnormal electrode behavior of graphite anode operating with the electrolyte containing vinylene carbonate and ethylene sulfite additives

Supplementing additives into the electrolyte is a simple and effective approach to improve the electrode performance of lithium-ion batteries (LIBs). Although vinylene carbonate (VC) and ethylene sulfite (ES) additives have been studied to improve the performance of LIBs with graphite anode, the abnormal electrode behavior of graphite anodes operating with the electrolyte containing VC and ES additives has never been reported. In this paper, we report on the discovery and interpretation of the room-temperature capacity anomaly of graphite anodes operating with the VC-ES electrolyte at relatively high C rates (≥ 0.5 C). A dynamic evolution mechanism of SEI is proposed on the basis of electrochemical analysis and surface examination of graphite anodes at different charge/discharge states. The merit of the VC-ES electrolyte over the VC electrolyte is found for graphite anodes operating at 55 ºC. The VC-ES electrolyte provided here holds great potential for application in LIBs with graphite anode operating at high temperatures.

Co-precipitation of red clover soluble protein with caseinate in the presence of antioxidant

The aim of the study was to investigate the effect of co-precipitation of red clover protein and casein in combination with sulphite. Previous studies have shown antioxidation effects of introducing sulphite in the extraction of red clover protein for potential food applications. In the present study, it was hypothesized that casein co-precipitation in combination with sulphite would improve red clover's protein recovery, quality, and protein digestibility. The amount of soluble protein in the red clover juice was increased by the presence of casein, determined by both an increase in the total protein and in the amount of the photosynthetic protein RuBisCO. Casein treatment did not affect the in vitro protein digestibility, whereas the digestibility was increased with the addition of sulphite as an effect of phenolic oxidation inhibition.

A novel strategy using sulfite for bromate control during UV/persulfate oxidation of bromide-containing waters

The ultraviolet/persulfate (UV/PS) process has attracted more and more attention for water treatment. However, it runs the risk of producing bromate in the presence of bromide ions. In this work, we propose a new strategy using sulfite to inhibit bromate formation. The results show that the addition of sulfite significantly reduced the formed bromate in the UV/PS system by 61.2% and 24.5% in 30 min and 120 min, respectively. Increasing sulfite dosage or pH could enhance bromate control. From the standpoint of reaction kinetics, sulfite is likely to inhibit bromate formation by reducing bromine radicals (Br) back to bromide ions, the energy profile of which was quantified by density functional theory (DFT) calculations. In the UV/PS/sulfite system, the conversion of SO3− to HO was observed, indicating that sulfite also served as a source of reactive radicals. Moreover, sulfite apparently promoted the degradation of benzoic acid and phenol in a UV/PS system, showing advantages over other inorganic reductants. As a result, we discovered that sulfite could not only help control bromate formation in UV/PS but also improve the system’s oxidation capacity.

Use of Oenological Tannins to Protect the Colour of Rosé Wine in a Bioprotection Strategy with Metschnikowia pulcherrima.

Although bioprotection is now recognised as an alternative to SO2 for limiting microbial spoilage, it does not guarantee protection against oxidation. This limits its application, more specifically for rosé winemaking. Oenological tannins present antioxidant properties, which could represent an interesting alternative to SO2 to protect must and wines against oxidation. A combination of the inoculation of a bioprotectant yeast strain and the addition of oenological tannins was tested to eliminate sulfites during the pre-fermentative step of rosé winemaking. In this experiment carried out in a winery, two oenological tannins were compared: quebracho and gall nut tannins. The antioxidant efficiency of tannins was compared to that of SO2. Colorimetric assays associated with chemical analyses of anthocyanins and phenolic compounds confirmed that the use of bioprotection alone did not protect the wine from oxidation. An addition of oenological tannins on musts stabilized the colour of bioprotected rosé wine in a similar way that SO2 addition did. Quebracho tannins appeared more efficient than gall nut tannins. The colour differences observed cannot be explained either by the concentration or forms of anthocyanins. However, the addition of tannins led to better protection of oxidation-sensitive phenolic compounds comparable to that obtained with the addition of sulfites.

Effects of reducing, stabilizing, and antibiotic agents on “Candidatus Kuenenia stuttgartiensis”

Anaerobic ammon ium oxidizing (anammox) bacteria oxidize ammonium and reduce nitrite, producing N2, and could play a major role in energy-optimized wastewater treatment. However, sensitivity to various environmental conditions and slow growth currently hinder their wide application. Here, we attempted to determine online the effect of environmental stresses on anammox bacteria by using an overnight batch activity test with whole cells, in which anammox activity was calculated by quantifying N2 production via headspace-pressure monitoring. A planktonic mixed culture dominated by “Candidatus Kuenenia stuttgartiensis” strain CSTR1 was cultivated in a 30-L semi-continuous stirring tank reactor. In overnight resting-cell anammox activity tests, oxygen caused strong inhibition of anammox activity, which was reversed by sodium sulfite (30 µM). The tested antibiotics sulfamethoxazole, kanamycin, and ciprofloxacin elicited their effect on a dose-dependent manner; however, strain CSTR1 was highly resistant to sulfamethoxazole. Anammox activity was improved by activated carbon and Fe2O3. Protein expression analysis from resting cells after anammox activity stimulation revealed that NapC/NirT family cytochrome c (KsCSTR_12840), hydrazine synthase, hydrazine dehydrogenase, hydroxylamine oxidase, and nitrate:nitrite oxidoreductase were upregulated, while a putative hydroxylamine oxidoreductase HAO (KsCSTR_49490) was downregulated. These findings contribute to the growing knowledge on anammox bacteria physiology, eventually leading to the control of anammox bacteria growth and activity in real-world application.Key Points• Sulfite additions can reverse oxygen inhibition of the anammox process• Anammox activity was improved by activated carbon and ferric oxide• Sulfamethoxazole marginally affected anammox activityGraphical abstract

Replacing the Addition of Sulfite in Mustard Pickle Products by High-Hydrostatic-Pressure Processing to Delay Quality Deterioration during Storage.

This study aimed to assess the use of the high-hydrostatic-pressure (HHP) method (200-600 MPa, 5 min) for bleaching mustard pickle products as an alternative to the conventional method of sulfite addition. The aerobic plate count (APC) and lactic acid bacteria count (LAB) of the samples decreased with the increase in pressure, and the yeast count decreased to no detectable levels. Next, compared with the control group (no high-pressure treatment) the L* (lightness), W (whiteness), ΔE (color difference), and texture (hardness and chewiness) of the HHP-processed samples, which increased significantly with increasing pressure, while the a* (redness) and b* (yellowness) values decreased slightly. This indicates that HHP processing gave the mustard pickle a harder texture and a brighter white color and appearance. Furthermore, when the mustard pickle was treated with HHP 400 and 600 MPa for 5 min and stored at 25 °C for 60 days, it was found that the APC and LAB counts in the HHP-processed group recovered rapidly and did not differ from those in the control group (the non-HHP treated group) but significantly delayed the growth of yeast, the increase in pH value, and total volatile basic nitrogen (TVBN). The high-throughput sequencing (HTS) analysis revealed that the predominant bacterial genera in the non-HHP-treated mustard pickle were Lactiplantibacillus (74%), Lactilactobacillus (12%), and Levilactobacillus (6%); after 60 days of storage, Companilactobacillus (80%) became dominant. However, after 60 days of storage, Lactiplantibacillus (92%) became dominant in the samples processed at 400 MPa, while Levilactobacillus (52%), Pediococcus (17%), and Lactiplantibacillus (17%) became dominant in the samples processed at 600 MPa. This indicated that the HHP treatment changed the lactic acid bacterial flora of the mustard pickle during the storage period. Overall, it is recommended to treat the mustard pickle with HHP above 400 MPa for 5 min to improve its texture and color and delay the deterioration of quality during storage. Therefore, HHP technology has the potential to be developed as a treatment technique to replace the addition of sulfite.

Sulfamethazine degradation by sulfite through GAC@Ni/Fe Three-Dimensional (3D) particle electrode activation: Contribution of active substance and synergy

The widespread production and use of antibiotics, which accumulate in the environment and lead to chronic poisoning of non-target organisms, causing potential safety risks to the environment and human health. In this study, GAC@Ni/Fe was used as particle electrode and sulfite hetero activator for synergistic degradation of Sulfamethazine(SMR) in a three-dimensional electrode reactor. Under the optimal experimental parameters (trough voltage = 5 V, sulfite addition =1 mM, particle electrode addition = 40 g, PH = 7), the removal rate of SMR can reach 96.91% within 30 min. The surface changes before and after the reaction at the GAC@Ni/Fe particle electrode was characterized using XRD, XPS, and FTIR. LSV, Tafel, and EIS were used to investigate the electrochemical performance of the GAC@Ni/Fe particle electrodes. The superiority of Three-Dimensional(3D) (GAC@Ni/Fe)/Sulfite system in SMR removal was confirmed by comparative experiments and reaction synergistic factor analysis. Electron paramagnetic resonance (EPR) and quenching experimental studies demonstrate that the degradation of SMR within the 3D (GAC@Ni/Fe)/Sulfite system is the result of both free radical and non-free radicals, with·OH, SO4−·and 1O2 contributing 51%, 12% and 37% to SMR removal, respectively. The 54.57% TOC removal rate (30 min) also demonstrates the efficient mineralization of SMR by the system. The results show that the 3D (GAC@Ni / Fe) / Sulfite system can be used to treat the wastewater containing SMR and other antibiotics, which is a green and ecologically friendly method with potential application value.

A novel and greener sequential column leaching approach for the treatment of two different Greek laterites

Τhe present study investigates, from an environmental protection viewpoint, the efficiency of sequential column leaching of two different Greek laterites, i.e. a limonitic ore from central and a saprolitic ore from northern Greece. First, the most refractory limonitic laterite is leached in the first column for 15 days and the obtained pregnant leach solution (PLS) is further used for the leaching of the easier to treat saprolitic ore in the second column, thus achieving a significantly reduced acid consumption. The main parameters affecting the process efficiency, i.e. acid molarity (1.5 or 3 mol/L H2SO4) and addition of sodium sulfite (Na2SO3) in the leaching solution were studied. The extraction of Ni, Co, Fe, Al, Mg, Mn and Ca was determined by Atomic Absorption Spectroscopy (AAS), while the characterization of the ores and final residues was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA/DTA), and Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM-EDS) analysis. The results confirm the efficiency of the proposed green approach, which with the use of leaching solution containing 1.5 mol/L H2SO4 and 20 g/L Na2SO3 resulted in 73.8 % Ni, 71.6 % Co and 8.4 % Fe extraction after a short period of time (33 days), while the acid consumption, which is a serious environmental concern, was very low and did not exceed 300 kg/t ore. Overall, the proposed process not only improves the efficiency of leaching of different types of laterites for the recovery of both Ni and Co but also reduces the environmental impacts due to the significantly lower acid consumption.

Preliminary Studies on the In Vitro Interactions Between the Secondary Metabolites Produced by Esca-Associated Fungi and Enological Saccharomyces cerevisiae Strains.

Esca-affected vines alter the carbohydrate metabolism, xylem transport of water and photosynthesis and show regular grapes (but berries do not reach maturity), and phenolic compounds are reduced in concentration, oxidate and polymerizate. Pullulan and a mixture of scytalone and isosclerone (9:1; w/w), secondary metabolites produced in vitro and in planta by Phaeoacremonium minimum (syn. P. aleophilum) and Phaeomoniella chlamydospora, were assayed against the strains Byosal HS1 and IOC 18-2007 in microvinifications with synthetic grape must. The presence of pullulan and pentaketides mix affects the growth and metabolism of the tested Saccharomyces cerevisiae strains. Assays at 100 and 1000 µg mL−1 inhibited the growth of both strains, while no effects were recorded when evaluated at 1 and 5 µg mL−1. In comparison with the controls, pullulan and the scytalone/isosclerone mixture at 10 µg mL−1 had a growth reduction, a lower alcohol yield, reduced the concentration of tartaric acid and malic acid; and slowed down the production of lactic acid, acetic acid and total polyphenol content of the tested S. cerevisiae strains. These metabolites could be applied as an alternative to the sulfite addition in the early stages of vinification to support the action of selected Saccharomyces. Appealing is the subtractive action of pullulan against tartaric acid. Further data are needed to confirm and validate the enological performance in freshly pressed grape juice.

The pathway for coenzyme M biosynthesis in bacteria

Mercaptoethane sulfonate or coenzyme M (CoM) is the smallest known organic cofactor and is most commonly associated with the methane-forming step in all methanogenic archaea but is also associated with the anaerobic oxidation of methane to CO2 in anaerobic methanotrophic archaea and the oxidation of short-chain alkanes in Syntrophoarchaeum species. It has also been found in a small number of bacteria capable of the metabolism of small organics. Although many of the steps for CoM biosynthesis in methanogenic archaea have been elucidated, a complete pathway for the biosynthesis of CoM in archaea or bacteria has not been reported. Here, we present the complete CoM biosynthesis pathway in bacteria, revealing distinct chemical steps relative to CoM biosynthesis in methanogenic archaea. The existence of different pathways represents a profound instance of convergent evolution. The five-step pathway involves the addition of sulfite, the elimination of phosphate, decarboxylation, thiolation, and the reduction to affect the sequential conversion of phosphoenolpyruvate to CoM. The salient features of the pathway demonstrate reactivities for members of large aspartase/fumarase and pyridoxal 5'-phosphate-dependent enzyme families.

The role of thiosulfate and sulfite in gold thiosulfate electrowinning process: An electrochemical view

In this study, electrochemical and analytical techniques are employed to explore the effect of thiosulfate, sulfite, and a mixture of thiosulfate-sulfite in the electrolyte on the gold electrowinning process. The open circuit potential (OCP) analysis showed negative potential shifts from − 0.02 V (in the electrolyte containing Au-TS (E1)) to − 0.21 V, − 0.33 V, and − 0.42 V in the presence of thiosulfate oversupply (electrolyte E2), sulfite (electrolyte E3), and thiosulfate-sulfite mixture (electrolyte E4). The linear sweep voltammetry (LSV) results exhibited − 0.4 V potential shift by the addition of sulfite to the gold-thiosulfate electrolyte, attributing to the formation of Au(S2O3)(SO3)25- as the most stable gold complex. Based on chronoamperometry (CA) and atomic absorption spectrometer (AAS) results, sulfite could control the kinetics and thermodynamics of gold reduction reactions by minimizing undesired cathodic side reactions such as thiosulfate decomposition or water reduction, resulting in purer gold deposition, elimination of colloidal sulfur, and a more efficient EW process. The presence of thiosulfate accelerated the kinetics of the gold reduction reaction. However, adding sulfite to the electrolyte stabilized the kinetic about 10 times faster. SEM and EDS analysis depicted the morphological changes in the deposited gold layer from different electrolytes during CA, showing that thiosulfate oversupply results in the formation of a greater number of smaller grains by accelerating the nucleation process, while sulfite addition led to the formation of a smoother and more uniform gold layer on the cathode surface.

Sulphite addition during steam pretreatment enhanced both enzyme-mediated cellulose hydrolysis and ethanol production

Sulphite addition during steam pretreatment of softwoods under acidic, neutral and alkaline conditions was assessed to try to minimize lignin condensation. Although pretreatment under neutral/alkaline conditions resulted in effective lignin sulphonation, non-uniform size reduction was observed. In contrast, acidic sulphite steam treatment at 210 °C for 10 min resulted in homogenous particle size reduction and water-insoluble component that was 62% carbohydrate and 33% lignin. This carbohydrate-rich substrate was readily hydrolyzed and fermented which indicated the lack of fermentation inhibitors in the steam-pretreated whole slurry. The use of high solid loading (25% w/v) resulted in a hydrolysis yield of 58% at an enzyme loading of 40 mg protein/g glucan and efficient fermentation (46.6 g/L of ethanol). This indicated that the addition of acidic sulphite at the steam pretreatment of softwoods improved both the enzymatic hydrolysis and fermentation of steam-pretreated whole slurries.Graphical

Detection and Stability of Cyanogen Bromide and Cyanogen Iodide in Drinking Water

This study systematically summarized the factors affecting the stability of CNXs, providing a reference for better control and elimination of CNXs. A method for the detection of CNBr and CNI in solution was established using a liquid–liquid extraction/gas chromatography/electron capture detector. Specifically, the method was used to investigate the stability of CNBr and CNI in drinking water, especially in the presence of chlorine and sulfite, and it showed good reproducibility (relative standard deviation &lt;3.05%), high sensitivity (method detection limit &lt;100 ng/L), and good recovery (91.49–107.24%). Degradation kinetic studies of cyanogen halides were conducted, and their degradation rate constants were detected for their hydrolysis, chlorination, and sulfite reduction. For hydrolysis, upon increasing pH from 9.0 to 11.0, the rate constants of CNCl, CNBr, and CNI changed from 8 to 155 × 10−5 s−1, 1.1 to 34.2 × 10−5 s−1, and 1.5 to 6.2 × 10−5 s−1, respectively. In the presence of 1.0 mg/L chlorine, upon increasing pH from 7.0 to 10.0, the rate constants of CNCl, CNBr, and CNI changed from 36 to 105 × 10−5 s−1, 15.8 to 49.0 × 10−5 s−1, and 1.2 to 24.2 × 10−5 s−1, respectively. In the presence of 3 μmol/L sulfite, CNBr and CNI degraded in two phases. In the first phase, they degraded very quickly after the addition of sulfite, whereas, in the second phase, they degraded slowly with rate constants similar to those for hydrolysis. Owing to the electron-withdrawing ability of halogen atoms and the nucleophilic ability of reactive groups such as OH− and ClO−, the rate constants of cyanogen halides increased with increasing pH, and they decreased in the order of CNCl &gt; CNBr &gt; CNI during hydrolysis and chlorination. The hydrolysis and chlorination results could be used to assess the stability of cyanogen halides in water storage and distribution systems. The sulfite reduction results indicate that quenching residual oxidants with excess sulfite could underestimate the levels of cyanogen halides, especially for CNBr and CNI.

Imaging fluctuation of sulfite in mouse tumor and inflammation models with a novel quinoxaline-based fluorescent probe

In this work, a novel fluorescent probe, YT, was developed for monitoring the fluctuation of sulfite in biological applications. The quinoxaline moiety was chosen as the fluorophore to obtain the naked-eye signals in the green channel. The levulinate was selected to achieve the specific and relatively steady recognition reaction. Compared with the reported fluorescent probes for sulfite, YT indicated above moderate performances including remarkable and rapid response (120 folds, within 10 min), high sensitivity (limit of detection = 0.15 μM), and high selectivity. The detecting system showed a green emission and the fluorescence was stable within the pH range of 6–10. In addition, YT could be further applied into living cells and mouse models. Focusing on the serviceability in the breadth of application scope, we imaged the fluctuation of sulfite in both mouse tumor and inflammation models. In the xenograft model, YT could indicate the fluctuation of sulfite which was caused by both addition of exogenous sulfite and induction of different agents including sulfite donor, Na2S2O3, phorbol-12-myristate-13-acetate, and GSH. In the LPS-induced inflammation model, YT could visualize the dose-dependent increase of sulfite level (0–2 mg/mL). More than providing a practical fluorescent implement for monitoring sulfite, this work also raised informatic parameters for developing fluorescent tools into broadened animal models.

Digestibility of seaweed protein from Ulva sp. and Saccharina latissima in rats

Seaweed is gaining attention as a sustainable source of protein. However, the nutritional protein quality needs further investigation to explore the potential of seaweed as a protein source. This study evaluates in vivo digestibility of six different seaweed protein products, four from Ulva sp. and two from Saccharina latissima. Ulva sp. was either preserved in a preservation liquid and spin flash-dried, freeze-dried without any pre-treatment or protein was extracted from the crude biomass with a screw press and isoelectrically precipitated (pH 2.5) with or without sulfite addition during extraction. Saccharina latissima was either freeze-dried or fermented with lactic acid bacteria prior to freeze-drying. The digestibility of the seaweed products was tested in a rat trial, where seaweed protein products constituted 50% of the nitrogen (N) in diets, the other 50% of N coming from whey protein concentrate. The protein concentration and proportion of essential amino acids (EAA) were increased upon protein extraction from Ulva sp. and the ash content was reduced. This led to an increased N digestibility of 55.5 ± 2.7% for the protein extract without sulfite, being 10–13%-points higher than for the other Ulva sp. products. The sulfite addition seemed to counteract the effect of extraction regarding the N digestibility. Fermentation of S. latissima increased the total amino acid content along with increased EAA proportion and lowered the ash content. However, the fermentation did not improve the organic matter, ash or N digestibility.Digestibility was in general low, but this study demonstrates the potential to increase seaweed N digestibility by more than 20% through protein extraction.