Effect of Stabilizer on Gold Leaching with Thiourea in Alkaline Solutions

The present work investigated the comparison of the effects of Na2SO3 and Na2SiO3 on thiourea stabilization, and a systematic study was undertaken to establish the effects of these stabilizers on the stability of alkaline thiourea, both qualitatively and quantitatively. The effects of these stabilizers on the activation energy of alkaline thiourea gold leaching was also studied. The results showed that sodium silicate was more suitable as a stabilizer in this system than sodium sulfite because the peak current of gold dissolution with sodium sulfite was higher than that with sodium silicate, but the inhibition of thiourea decomposition by the former was less obvious than that of sodium silicate in the cyclic voltammetry curve. The quartz crystal microbalance results showed that the quality decreased to about 100 ng cm2 in the presence of a stabilizer, while it increased to 300 ng cm2 in the absence of the stabilizer. It is inferred that gold can be dissolved by alkaline thiourea in the presence of a stabilizer, while it cannot without a stabilizer because of the decomposition of thiourea. This assumption was confirmed by atomic force microscopy measurements. The surface activation energy of Au dissolution decreased from 183.76 to 98.07 kJ/moL with the addition of sodium silicate, indicating that Au dissolution was promoted with the chemical.

Evidence from Thermal Aging Indicating That the Synergistic Effect of Glyoxal and Sodium Sulfite Improved the Thermal Stability of Conformational Modified Xanthan Gum

Xanthan gum is prone to thermal oxidative degradation, which limits its applications. However, conformational changes in xanthan gum and appropriate stabilizers may improve its thermal stability. Therefore, in this study, we aimed to establish a strategy to maintain the viscosity of xanthan gum during long-term storage at high temperatures. We modified the original strain used for xanthan gum production by genetic engineering and added stabilizers during the production process. The structure and thermal stability of the resulting xanthan gum samples were then determined. Pyruvyl deficiency, combined with the addition of sodium sulfite and glyoxal during the production process, was found to significantly improve the maintenance of viscosity. The apparent viscosity of the new xanthan gum solution remained above 100 mPa·s after being stored at 90 °C for 48 days. Fourier-transform infrared spectra and scanning electron microscopy images showed that pyruvate-free xanthan gum with added stabilizers had more extensive cross-linking than natural xanthan gum. In conclusion, these findings may contribute to the use of xanthan gum in applications that require high temperatures for a long period of time.

Sulfite preservatives effects on the mouth microbiome: changes in viability, diversity and composition of microbiota

Processed foods make up about 70 percent of the American diet. Sulfites and other food preservatives are added to these foods largely to limit bacterial contamination. The mouth microbiota and its associated enzymes are the first to encounter food and therefore likely to be the most affected. Eight saliva samples from ten individuals were exposed to two sulfite preservatives, sodium sulfite and sodium bisulfite. One sample set was evaluated for bacteria composition utilizing 16s rRNA sequencing, and the number of viable cells in all sample sets was determined utilizing ATP assays at 10 and 40-minute exposure times. All untreated samples were analyzed for baseline lysozyme activity, and possible correlations between the number of viable cells and lysozyme activity. Sequencing results indicated significant increases in alpha diversity with sodium bisulfite exposure and changes in relative abundance of 3 amplicon sequence variants (ASV). Sodium sulfite treated samples showed a significant decrease in the Firmicutes/Bacteroidetes ratio, a marginally significant change in alpha diversity, and a significant change in the relative abundance for Proteobacteria, Firmicutes, Bacteroidetes, and for 6 ASVs. Beta diversity did not show any separation between groups, however, all but one sample set was observed to be moving in the same direction under sodium sulfite treatment in a principal component analysis. ATP assays indicated a significant and consistent average decrease in activity ranging from 24 - 46% at both exposure times with both sulfites. Average initial rates of lysozyme activity between all individuals ranged from ± 76% compared to individual variations of 10 - ± 34%. No consistent, significant correlation was found between ATP and lysozyme activity in any sample sets. Conclusions: Sulfite preservatives, at concentrations regarded as safe by the FDA, alter the relative abundance and richness of the microbiota found in saliva, and decrease the number of viable cells, within 10 minutes of exposure.

CONDENSED TANNINS OF THE SPECIES PINUS TAEDA: EXTRACTION, CHARACTERIZATION AND POTENTIAL FORMULATION OF WOOD BIOADHESIVE

The species Pinus taeda was evaluated as a source of condensed tannins for the potential formulation of phenolic adhesives from the extraction of the wood cortex. Extraction yield, percentage of tannins and non-tannins, and reactivity to the formaldehyde by the Stiasny number were analyzed in the responses of the extraction processes with extractive agents sodium sulfite (Na2SO3), sodium hydroxide (NaOH), and urea [(NH2)2CO] in the percentages of 2, 4, 6, 8, and 10 in relation to the weight of the bark of this species. The extracts were analyzed using the techniques of IR - Infrared Spectroscopy, SEM - Scanning Electron Microscopy, DRX- X-ray Diffractometry, and EDS - Energy-Dispersive X-ray Spectrometry. In another step, the formation time of the commercial tannin gel and of the P. taeda were compared in relation to formaldehyde. The results show that the specie have condensed tannins, and sustain that they are catechins. These catechins form polymers identified by SEM in less time in relation to the formaldehyde in the formation of the gel, suggesting that the tannins can be extracted from the species as a potentially new commercial source that lumber companies can use to manufacture phenolic resins.

An effect of food additives on microbiome

The paper presents a review of available data about an effect of food additives on the human microbiome and lists the main physiological functions of the gut microbiome. The process of the human microbiome evolution is examined. The relationship between the emergence of a disease and the microbiome composition, as well as the main factors influencing the gut microbiome composition are described. The main food additives used today are listed, their key features are discussed and their structural formulas are given. The information about their effect on the human body through an influence on the microbiome composition is presented. The data on an effect of polysorbate 80, carboxymethylcellulose, sodium sulfite, nisin, potassium sorbate, sodium benzoate, sodium nitrate, essential oils, titanium dioxide and different sweeteners on the microbiome are analyzed. It is explained what microbial communities are suppressed and what communities gain advantages in multiplication when consumers eat food with one or another food additive. The consequences of alterations in the microbiome for the consumer’s body are examined. Conclusions were made about the necessity of additional studies about an effect of food additives on the composition of the human microbiome.

Sodium sulfite as a switching agent for single molecule based super-resolution optical microscopy

Photoinduced off-switching of organic fluorophores is routinely used in super-resolution microscopy to separate and localize single fluorescent molecules, but the method typically relies on the use of complex imaging buffers. The most common buffers use primary thiols to reversibly reduce excited fluorophores to a non-fluorescent dark state, but these thiols have a limited shelf life and additionally require high illumination intensities in order to efficiently switch the emission of fluorophores. Recently a high-index, thiol-containing imaging buffer emerged which used sodium sulfite as an oxygen scavenger, but the switching properties of sulfite was not reported on. Here, we show that sodium sulfite in common buffer solutions reacts with fluorescent dyes, such as Alexa Fluor 647 and Alexa Fluor 488 under low to medium intensity illumination to form a semi-stable dark state. The duration of this dark state can be tuned by adding glycerol to the buffer. This simplifies the realization of different super-resolution microscopy modalities such as direct Stochastic Reconstruction Microscopy (dSTORM) and Super-resolution Optical Fluctuation Microscopy (SOFI). We characterize sulfite as a switching agent and compare it to the two most common switching agents by imaging cytoskeleton structures such as microtubules and the actin cytoskeleton in human osteosarcoma cells.

Electrochemical Deposition of ZnS Films from Electrolyte Based on Na2SO3

The paper considers the features of electrochemical growth of zinc sulfide from an aqueous electrolyte based on sodium sulfite and zinc sulfate. The conditions for the electrochemical production of ZnS films are determined. It is shown that the value of the potential at which a ZnS layer is formed is limited by the achievement of the critical current due to the diffusion limitations of the electrochemical process of reducing the sulfite ion. It is shown that the resulting films contain an excess of sulfur, which is removed, and the stoichiometric composition is obtained by heat treatment. Aed mechanism of reactions resulting in the formation of zinc sulfide is proposed.