Wiping conditions and fabric properties influenced the microfiber shedding from non-woven products.

Disposable wipes and masks have come to be considered as underestimated sources of microfiber generation since the emergence of COVID-19. However, research into the creation of microfibers due to wiping with these non-woven products is scarce, and the potential effects of fabric properties on shedding behavior are unclear. This study investigated microfiber release from 7 wet wipes, 5 dry wipes, and 4 masks in response to the use of simulated daily wiping conditions on artificial skin. The dry wipes (77-568 p per sheet) shed more microfibers than the wet ones (21-190 p per sheet) after 2, 10, or 50 wiping cycles under a 9.8 N wiping force. In addition, an average of 56 microfibers could be released from per gram of wipe, and each square centimeter of wipe could release about 1.18 microfibers during wiping. Masks shed fewer microfibers than wipes due to the excellent shedding resistance of spunbond nonwoven fabrics and the strengthened mechanical properties granted by bonding points. Cellulose, polyethylene terephthalate (PET), and polypropylene (PP) were the major polymers in the microfibers shed by wipes, and the microfibers from masks were all PP. With regard to the influencing factors, the number of microfibers shed from wipes was positively associated with the number of wiping cycles (r = 0.983 and 0.960, p < 0.01) and wiping force (r = 0.980, p < 0.05), while it was negatively correlated with the moisture content (r = -0.992, p < 0.01). Interestingly, a stronger fiber entanglement degree in the wipes significantly improved the resistance to microfiber generation (r = -0.664, p < 0.05). The results highlighted for the first time that the bending coefficient (ß = -5.05; 95% CI: -7.71, -2.40; p = 0.002) and fiber extraction force (ß = -0.077; 95% CI: -0.123, -0.030; p = 0.005) significantly reduced the tendency for microfiber shedding. Although the number of microfibers shed from wiping was lower than those from domestic washing, there is still an urgent need to control the microfiber shedding tendencies of non-woven products through improving the manufacturing processes.

Biochemical characterization of a novel azo reductase named BVU5 from the bacterial flora DDMZ1: application for decolorization of azo dyes.

One of the main mechanisms of bacterial decolorization and degradation of azo dyes is the use of biological enzymes to catalyze the breaking of azo bonds. This paper shows the expression and properties of a novel azo reductase (hybrid-cluster NAD(P)-dependent oxidoreductase, accession no. A0A1S1BVU5, named BVU5) from the bacterial flora DDMZ1 for degradation of azo dyes. The molecular weight of BVU5 is about 40.1 kDa, and it contains the prosthetic group flavin mononucleotide (FMN). It has the decolorization ability of 80.1 ± 2.5% within 3 min for a dye concentration of 20 mg L-1, and 53.5 ± 1.8% even for a dye concentration of 200 mg L-1 after 30 min. The optimum temperature of enzyme BVU5 is 30 °C and the optimum pH is 6. It is insensitive to salt concentration up to a salinity level of 10%. Furthermore, enzyme BVU5 has good tolerance toward some metal ions (2 mM) such as Mn2+, Ca2+, Mg2+ and Cu2+ and some organic solvents (20%) such as DMSO, methanol, isopentyl, ethylene glycol and N-hexane. However, the enzyme BVU5 has a low tolerance to high concentrations of denaturants. In particular, it is sensitive to the denaturants guanidine hydrochloride (GdmCl) (2 M) and urea (2 M). Analysis of the dye substrate specificity shows that enzyme BVU5 decolorizes most azo dyes, which is indicating that the enzyme is not strictly substrate specific, it is a functional enzyme for breaking the azo structure. Liquid chromatography/time-of-flight/mass spectrometry (LC-TOF-MS) revealed after the action of enzyme BVU5 that some intermediate products with relatively large molecular weights were produced; this illustrates a symmetric or an asymmetric rapid cleavage of the azo bonds by this enzyme. The potential degradation pathways and the enzyme-catalyzed degradation mechanism are deduced in the end of this paper. The results give insight into the potential of a rapid bio-pretreatment by enzyme BVU5 for processing azo dye wastewater.

Deciphering the mechanism of carbon sources inhibiting recolorization in the removal of refractory dye: Based on an untargeted LC-MS metabolomics approach.

In this study, the biological decolorization of reactive black 5 (RB5) by Klebsiella sp. KL-1 in yeast extract (YE) medium was captured the recolorization after exposure to O2, which induced a 15.82% reduction in decolorization efficiency. Similar result was also observed in YE + lactose medium, but not in YE + glucose/xylose media (groups YE + Glu/Xyl). Through biodegradation studies, several degradation intermediates without quinoid structure were produced in groups YE + Glu/Xyl and differential degradation pathways were deduced in diverse groups. Metabolomics analysis revealed significant variations in up-/down-regulated metabolites using RB5 and different carbon sources. Moreover, the underlying mechanism of recolorization inhibition was proposed. Elevated reducing power associated with variable metabolites (2-hydroxyhexadecanoic acid, 9(R)-HODE cholesteryl ester, linoleamide, oleamide) rendered additional reductive cleavage of C-N bond on naphthalene ring. This study provided a new orientation to inhibit recolorization and deepened the understanding of the molecular mechanism of carbon sources inhibiting recolorization in the removal of refractory dyes.

Co-metabolic degradation of refractory dye: A metagenomic and metaproteomic study.

Fructose was utilized as an additional co-substrate to systematically investigate the molecular mechanism of its boosting effect for the degradation of refractory dye reactive black 5 (RB5) by a natural bacterial flora DDMZ1. A decolorizing rate of 98% was measured for sample YE + FRU(200) (with 3 g/L fructose additionally to yeast extract medium, 10% (v/v) inoculation size of flora DDMZ1, 200 mg/L RB5) after 48 h. This result was 21% and 77%, respectively, higher than those of samples with only yeast extract or only fructose. Fructose was found to significantly stimulated both intracellular and extracellular azoreductase secretion causing enhanced activity. Metagenomic sequencing technology was used to analyze the functional potential of genes. A label-free quantitative proteomic approach further confirmed the encoding of functional proteins by the candidate genes. Subsequently, the molecular mechanism of RB5 degradation by candidate genes and functional proteins of the dominant species were proposed. This study provides important perspectives to the molecular mechanism of co-metabolic degradation of refractory pollutants by a natural bacterial flora.

Sugar sources as Co-substrates promoting the degradation of refractory dye: A comparative study.

Four sugar sources were used as co-substrates to promote the degradation of a selected refractory dye reactive black 5 (RB5) by the natural bacterial flora DDMZ1. The boosting performance of the four sugar sources on RB5 decolorization ranked as: fructose > sucrose > glucose > glucose + fructose. Kinetic results of these four co-metabolism systems agreed well with a first-order kinetic model. Four sugar sources stimulated the extracellular azoreductase secretion causing enhanced enzyme activity. An increased formation of low molecular weight intermediates was caused by the addition of sugar sources. The toxicity of RB5 degradation products was significantly reduced in the presence of sugar sources. The bacterial community structure differed remarkably as a result of sugar sources addition. For a fructose addition, a considerably enriched population of the functional species Burkholderia-Paraburkholderia and Klebsiella was noted. The results enlarge our knowledge of the microkinetic and microbiological mechanisms of co-metabolic degradation of refractory pollutants.

Unveiling the activating mechanism of tea residue for boosting the biological decolorization performance of refractory dye.

Conventional microbial treatments are challenged by new synthetic refractory dyes. In this work, tea residue was found serving as an effective activator to boost the decolorization performance of anthraquinone dye (reactive blue 19, RB19) by a new bacterial flora DDMY2. The unfermented West Lake Longjing tea residue showed the best enhancement performance. Seventeen main kinds of components in tea residue had been selected to take separate and orthogonal experiments on decolorization of RB19 by DDMY2. Results suggested epigallocatechin gallate (EGCG) in tea residue played important roles in boosting the treatment performance. Illumina MiSeq sequencing results confirmed that EGCG and tea residue pose similar impact on the change of DDMY2 community structure. Some functional bacterial genera unclassified_o_Pseudomonadales, Stenotrophomonas and Bordetella were enriched during the treatment of RB19 by EGCG and tea residue. These evidences suggested EGCG might be the key active component in tea residue that responsible for the enhancement effect on decolorization performance. These results revealed the activating mechanism of tea residue from the perspective of composition.

Fructose as an additional co-metabolite promotes refractory dye degradation: Performance and mechanism.

In this work, the performance and mechanism for the boosting effects of fructose as an additional co-metabolite towards the biological treatment of reactive black 5 were systematically investigated. A decolorization efficiency of 98% was obtained in sample FRU200 (with 3 g/L fructose added based on 3 g/L yeast extract), which was 21% higher than that without fructose. Several intermediates with low molecular weight generated in sample FRU200 and different metabolic pathways were deduced. The bacterial community structure significantly changed due to fructose addition. Label-free quantitative proteomic approach suggested that several up-regulated proteins in sample FRU200 might play essential roles during the degradation. Furthermore, the mechanisms of RB5 degradation by proteins/enzymes of the dominant species in flora DDMZ1 were proposed. This work deepens our understanding of the molecular and ecological mechanism of fructose as co-metabolite enhancing the biodegradation of refractory organic pollutants by a natural bacterial flora.

Highly efficient biodegradation of reactive blue 19 under the activation of tea residue by a newly screened mixed bacterial flora DDMY2.

In this study, a newly screened mixed bacterial flora DDMY2 had high decolorization capacity for anthraquinone dye reactive blue 19 (RB19) and the decolorization efficiency of 300 mg L-1 RB19 could reach up to 98% within 48 h in the presence of tea residue. Results indicated that RB19 could be efficiently decolorized by flora DDMY2 in wide ranges of pH values (5.0-9.0), temperatures (30-40 °C) and initial dye concentrations (50-500 mg L-1) under the activation of tea residue. Concentration of tea residue had been proved to significantly impact the decolorization performance. UV-vis spectrophotometry, Fourier transform infrared spectrometry and liquid chromatography/time-of-flight/mass spectrometry analysis showed three identified degradation products and the possible degradation pathway of RB19 was speculated. High-throughput sequencing analysis revealed the community structures of bacterial flora before and after domestication by tea residue. Based on the result, it was inferred that unclassified_o_Pseudomonadales, Brevibacillus, Stenotrophomonas and Bordetella activated by tea residue were responsible for the excellent decolorization performance. Results of this research deepen our understanding of the biodegradation process of anthraquinone dyes by bacterial flora and broaden the knowledge of utilizing tea residue as a bioactivator in biological treatment.