A ratiometric fluorescence probe for bisulfite detection in live cells and meat samples.

The development of reliable probe technology for the detection of bisulfite (HSO3-) in situ in food and biological samples is contributing significantly to food quality and safety assurance as well as community health. In this work, a responsive probe, EHDI, is developed for ratiometric fluorescence detection of HSO3- in aqueous solution, meat samples, and living cells. The probe is designed based on the HSO3- triggered 1,4-addition of electron deficit C = C bond of EHDI. As a result of this specific 1,4-addition, the π-conjugation system was destructed, resulting in blue shifts of the emission from 687 to 440 nm and absorption from 577 to 355 nm. The probe has good water solubility, high sensitivity and selectivity, allowing it to be used for imaging of HSO3- internalization and production endogenously. The capability of probe EHDI for HSO3- was then validated by traditional HPLC technology, enabling accurately detect HSO3- in beef samples. The successful development of this probe thus offers a new tool for investigating HSO3- in situ in food and biological conditions.

Mitochondria-targeted fluorescent probe for simultaneously imaging viscosity and sulfite in inflammation models.

Many diseases in the human body are related to the overexpression of viscosity and sulfur dioxide. Therefore, it is essential to develop rapid and sensitive fluorescent probes to detect viscosity and sulfur dioxide. In the present work, we developed a dual-response fluorescent probe (ES) for efficient detection of viscosity and sulfur dioxide while targeting mitochondria well. The probe generates intramolecular charge transfer by pushing and pulling the electron-electron system, and the ICT effect is destroyed and the fluorescence quenched upon reaction with sulfite. The rotation of the molecule is inhibited in the high-viscosity system, producing a bright red light. In addition, the probe has good biocompatibility and can be used to detect sulfite in cells, zebrafish and mice, as well as upregulation of viscosity in LPS-induced inflammation models. We expect that the dual response fluorescent probe ES will be able to detect viscosity and sulfite efficiently, providing an effective means of detecting viscosity and sulfite-related diseases.

A FRET-based multifunctional fluorescence probe for the simultaneous detection of sulfite and viscosity in living cells.

Viscosity and sulfur dioxide derivatives were significant indicators for the assessment of health threat and even cancers, therefore, on-site and real time detection of viscosity and sulfur dioxide derivatives has obtained considerable attentions. An FRET-based fluorescence probe JZX was designed and synthesized based on a novel energy donor of N,N-diethyl-4-(1H-phenanthro[9,10-d]imidazol-2-yl)benzamide fluorophore. JZX exhibited a large Stokes shift (230 nm), high energy transfer efficiency, wide emission channel gap (135 nm) and excellent stability and biocompatibility. JZX detected sulfur dioxide with low detection limit (55 nM), fast responding (16 min), high selectivity and sensitivity. Additionally, JZX tend to target endoplasmic reticulum of which normal metabolism will be disturbed by the abnormal levels of viscosity and sulfur dioxide derivatives. Prominently, JZX could concurrently detect viscosity and sulfur dioxide derivatives depending on different fluorescence signals in living cells for the screening of cancer cells. Hence, probe JZX will be a promising candidate for the detection of viscosity and sulfur dioxide derivatives, and even for the diagnosis of liver cancers.

Developing a fluorescent probe containing benzofuranone moiety for imaging sulphite in living hypoxia pulmonary cells.

In this work, a benzofuranone-derived fluorescent probe BFSF was developed for imaging the sulphite level in living hypoxia pulmonary cells. Under the excitation of 510 nm, BFSF showed a strong fluorescence response at 570 nm when reacted with sulphite. In the solution system, the constructed hypercapnia and serious hypercapnia conditions did not affect the fluorescence response. In comparison with the recently reported probes, BFSF suggested the advantages including rapid response, steady signal reporting, high specificity and low cytotoxicity upon living lung cells. Under a normal incubation atmosphere, BFSF realized the imaging of both exogenous and endogenous sulphite in living pulmonary cells. In particular, BFSF achieved imaging the decrease of the sulphite level under severe hypoxia as well as the recovery of the sulphite level with urgent oxygen supplement. With the imaging capability for the sulphite level in living pulmonary cells under hypoxia conditions, BFSF together with the information herein was meaningful for investigating the anaesthesia-related biological indexes.

Determination of Sulfites in Dried Fruits by Paper Spray Ionization Tandem Mass Spectrometry.

Sulfite, a widely used food additive, is subject to regulated labeling. The extraction of sulfite as the stable hydroxymethylsulfonate (HMS) form and its quantitative analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been recognized for their good sensitivity, selectivity, and versatility across various food materials. This study aimed to develop a cost-effective and simpler method for sulfite quantitation, while maintaining the superior sensitivity and selectivity of mass spectrometry (MS). To achieve this, we introduced paper spray ionization (PSI), an ambient desorption ionization technique that could achieve the direct measurement of analytes without employing separation. We also employed a novel internal standard (IS) structurally similar to the analyte, replacing the more expensive isotopically labeled IS. Although the PSI-MS/MS method developed in this study exhibited slightly lower analytical performance compared to the conventional LC-MS/MS, it remained effective for sulfite analysis in dried fruits.

Disposable Microchamber with a Microfluidic Paper-Based Lid for Generation and Membrane Separation of SO2 Gas Employing an In Situ Electrochemical Gas Sensor for Quantifying Sulfite in Wine.

This work presents a fully disposable microchamber for gas generation of a sample solution. The microchamber consists of a cylindrical well-reactor and a paper-based microfluidic lid (µFluidic lid), which also serves as the reagent loading and dispensing unit. The base of the reactor consists of a hydrophobic membrane covering an in-house graphene electrochemical gas sensor. Fabrication of the gas sensor and the three-layer µFluidic lid is described. The µFluidic lid is designed to provide a steady addition of the acid reagent into the sample solution instead of liquid drops from a disposable syringe. There are three steps in the procedure: (i) acidification of the sample in the reactor to generate SO2 gas by the slow dispensing of the acid reagent from the µFluidic lid, (ii) diffusion of the liberated SO2 gas through the hydrophobic membrane at the base of the reactor, and (iii) in situ detection of SO2 by cathodic reduction at the graphene electrode. The device was demonstrated for quantitation of the sulfite preservative in wine without heating or stirring. The selectivity of the analysis is ensured by the combination of the gas-diffusion membrane and the selectivity of the electrochemical sensor. The linear working range is 2-60 mg L-1 SO2, with a limit of detection (3SD of intercept/slope) of 1.5 mg L-1 SO2. This in situ method has the shortest analysis time (8 min per sample) among all voltammetric methods that detect SO2(g) via membrane gas diffusion.

Desulfofustis limnaeus sp. nov., a freshwater sulfate-reducing bacterium isolated from marsh soil.

A novel sulfate-reducing bacterium, strain PPLLT, was isolated from marsh soil. Cells of strain PPLLT were rod-shaped with length of 1.5 µm and width of 0.7 µm. Growth was observed at 22-37 °C (optimum 35 °C) and pH 6.8-8.4 (optimum 7.3). Lactate, succinate, fumarate, formate and malate were utilized as electron donors for sulfate reduction. Fermentative growth was not observed on tested organic acids. Besides sulfate, sulfite, thiosulfate and elemental sulfur were utilized as electron acceptors. Hydrogen is used only in the presence acetate or yeast extract. The major fatty acid was C16:0. The complete genome of strain PPLLT was composed of a circular chromosome with length of 4.2 Mbp and G + C content of 57.7 mol%. Sequence analysis of the 16S rRNA gene showed that strain PPLLT was affiliated with the genus Desulfofustis in the family Desulfocapsaceae. On the basis of differences in the phylogenetic and phenotypic properties between the strain and the type strain of the genus Desulfofustis, strain PPLLT (DSM 110475T = JCM 39161T) is proposed as the type strain of a new species, with name of Desulfofustis limnaeus sp. nov.

Desulfoluna limicola sp. nov., a sulfate-reducing bacterium isolated from sediment of a brackish lake.

A novel sulfate-reducing bacterium, strain ASN36T, was isolated from sediment of a brackish lake in Japan. Cells of strain ASN36T were not motile and rod-shaped, with length of 2.0-4.9 µm and width of 0.6-0.9 µm. Growth was observed at 5-35 °C with an optimum growth temperature of 25-30 °C. The pH range for growth was 6.6-8.8 with an optimum pH of 7.3. Major fatty acids were C16:1 ω7c and C16:0. Under sulfate-reducing conditions, strain ASN36T utilized lactate, malate, pyruvate, butyrate, ethanol, butanol, glycerol, yeast extract and H2/CO2 as growth substrate. Fermentative growth occurred on malate and pyruvate. The novel isolate used sulfate, sulfite and thiosulfate as electron acceptors. The genome of strain ASN36T is composed of a chromosome with length of 6.3 Mbp and G + C content of 55.1 mol%. Analyses of the 16S rRNA gene indicated that strain ASN36T is related to Desulfoluna species. Overall genome relatedness indices indicated that strain ASN36T does not belong to any existing species. In contrast to the closest relatives, strain ASN36T lacks genes for reductive dehalogenase required for organohalide respiration and does not use halogenated aromatics as electron acceptors. On the basis of its genomic and phenotypic properties, strain ASN36T (= DSM 111985 T = JCM 39257 T) is proposed as the type strain of a new species, Desulfoluna limicola sp. nov.

Induced sulfur metabolism by sulfur dioxide maintains postharvest quality of 'Thompson Seedless' grape through increasing sulfite content.

BACKGROUND: The commercial preservation of table grapes largely depends on the application of sulfur dioxide (SO2 ). However, little is known about whether SO2 participates in sulfur metabolism to improve the postharvest quality of table grapes. In this study, the contents of sulfur-containing compounds, activities of enzymes, and expression of genes involved in sulfur metabolism in table grapes (Vitis vinifera cv. Thompson Seedless) were evaluated. RESULTS: The results indicated that SO2 treatment maintained the postharvest quality of table grapes. The sulfite content in rachises and berries, but not the sulfate content, increased in response to SO2 treatment. SO2 caused high activities of sulfite reductase, O-acetylserine (thiol)-lyase, and γ-glutamylcysteine synthetase, thereby increasing the contents of cysteine, hydrogen sulfide, and glutathione in the rachises and berries. The expression of VvSURTL, VvATPS1, VvATPS2, and VvAPR3 decreased in response to SO2 treatment; however, the transcript levels of VvSiR1 and VvOASTL exhibited the opposite tendency. CONCLUSION: These findings indicated that the sulfite converted from SO2 participated in sulfur metabolism and maintained the postharvest quality of table grapes by modulating the contents of metabolites, activities of enzymes, and expression of genes related to sulfur metabolism. © 2021 Society of Chemical Industry.

Baseline composition and microbial quality assessment of raw milk from small ruminants and Maghrebi camels in the oasis area of Tunisia.

The milk quality and characteristics of the local Gharbi sheep and autochthonous goat population were studied and compared to those of the local Maghrebi camel. Milk samples from 378 lactating animals raised in the Tunisian oasis region were obtained and processed for various physicochemical compositions (pH, density, acidity, dry matter, fat, protein, lactose, casein, ash, and casein-protein ratio), mineral concentrations (Ca, P, Na, and K), and bacteriological properties (total mesophilic aerobic bacteria (TMAB), total coliform count (TCC), lactic acid bacteria (LAB), sulfite-reducing Clostridium (CSR), yeast and molds (Y/M), Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Salmonella) using standard methods. Milk from sheep breeds had a higher average of all physical parameters (pH, density, and dornic acidity) than milk from goat species. The sheep population produced milk with a similar pH to the camel population, but with a higher density and acidity content. The pH and acidity were higher in Neggas than in goat species, while density was similar in both. For chemical composition, the results showed significant heterogeneity in milk content across all species. Except for the casein-protein ratio, which favors goat species, the analysis indicates that sheep species were superior to populations of goats and camels in all chemical compositions. The present results showed considerable variation in the mineral content of milk from different species. The levels of calcium and phosphorus are higher in sheep than in goat and camel milk. Compared to small ruminants, milk from camels is the richest in Na and K. Additionally, more calcium is present in the milk of camels than that of goats. Goat milk, the lowest in Ca and Na, contains more P than camel milk and more K than sheep's milk on average. The poorest microbial quality was that of camel milk for all bacterial counts. Based on TMAB, TCC, and E. coli counts, the microbiological quality of goat milk was higher than that of ovine milk, while ovine milk had better quality based on LAB, Y/M, and S. aureus values. For Escherichia coli and Staphylococcus aureus, there were no significant variations between the species studied. Results showed that all milk samples studied were completely free of two dangerous pathogens, Salmonella and sulfite-reducing Clostridium. The bacteriological quality of small ruminant's milk was acceptable and met the regulatory limits set by Tunisian dairy legislation. Regarding camel milk, the microbial analysis revealed poor quality that exceeds standard criteria.