pH-dependent and whole-cell catalytic decolorization of dyes using recombinant dye-decolorizing peroxidase from Rhodococcus jostii

Dyes in wastewater have adverse effects on the environment and human health. Dye-decolorizing peroxidase (DyP) is a promising biocatalyst to dyes degradation, but the decolorization rates varied greatly which influencing factors and mechanisms remain to be fully disclosed. To explore an effective decolorizing approach, we have studied a DyP from Rhodococcus jostii (RhDyPB) which was overexpressed in Escherichia coli to decolorize four kinds of dyes, Reactive blue 19, Eosin Y, Indigo carmine, and Malachite green. We found the decolorization rates of the dyes by purified RhDyPB were all pH-dependent and the highest one was 94.4% of Malachite green at pH 6.0. ESI-MS analysis of intermediates in the decolorization process of Reactive blue 19 proved the degradation was due to peroxidase catalysis. Molecular docking predicated the interaction of RhDyPB with dyes, and a radical transfer reaction. In addition, we performed decolorization of dyes with whole E. coli cell with and without expressing RhDyPB. It was found that decolorization of dyes by E. coli cell was due to both cell absorption and degradation, and RhDyPB expression improved the degradation rates towards Reactive blue 19, Indigo carmine and Malachite green. The effective decolorization of Malachite green and the successful application of whole DyP-overexpressed cells in dye decolorization is conducive to the bioremediation of dye-containing wastewaters by DyPs.

Cobalt-Catalyzed Asymmetric Aza-Nozaki-Hiyama-Kishi (NHK) Reaction of α-Imino Esters with Alkenyl Halides

Chromium-catalyzed enantioselective Nozaki-Hiyama-Kishi (NHK) reaction represents one of the most powerful approaches for the formation of chiral carbon-heteroatom bond. However, the construction of sterically encumbered tetrasubstituted stereocenter through NHK reaction still posts a significant challenge. Herein, we disclose a cobalt-catalyzed aza-NHK reaction of ketimine with alkenyl halide to provide a convenient synthetic approach for the manufacture of enantioenriched tetrasubstituted α-vinylic amino acid. This protocol exhibits excellent functional group tolerance with excellent 99 % ee in most cases. Additionally, this asymmetric reductive method is also applicable to the aldimine to access the trisubstituted stereogenic centers.

Effects of In Vitro Fermentation of Polysialic Acid and Sialic Acid on Gut Microbial Community Composition and Metabolites in Healthy Humans

The influence of polysialic acid (PSA) and sialic acid (SA) on the gut microbial community composition and metabolites in healthy humans was investigated using a bionic gastrointestinal reactor. The results indicated that PSA and SA significantly changed the gut microbiota and metabolites to different degrees. PSA can increase the relative abundances of Faecalibacterium and Allisonella, whereas SA can increase those of Bifidobacterium and Megamonas. Both can significantly increase the content of short-chain fatty acids. The results of metabolome analysis showed that PSA can upregulate ergosterol peroxide and gallic acid and downregulate the harmful metabolite N-acetylputrescine. SA can upregulate 4-pyridoxic acid and lipoic acid. PSA and SA affect gut microbiota and metabolites in different ways and have positive effects on human health. These results will provide a reference for the further development of PSA- and SA-related functional foods and health products.

Allergic Phenotypes and Sarcopenia: Evidence from Observational Studies and Mendelian Randomization Analysis

Commonly affected in early-life population, the impact of allergic phenotypes on mid- or late-life health is less discussed. This study is to explore the association of allergic phenotypes including atopic dermatitis (AD), asthma, eosinophils count (EC), and sarcopenia. We conducted observational studies and mendelian randomization (MR) analysis based on UK Biobank (UKB), the China Health and Retirement Longitudinal Study (CHARLS) and data from genome-wide association study (GWAS). Based on the UKB data, AD, asthma and EC were positively correlated with pre-sarcopenia and decreased skeletal muscle mass index and hand grip in fully adjusted model. Asthma and EC were significantly associated with sarcopenia while AD was marginally associated (p = 0.095). Based on the CHARLS cohort, asthma significantly added 109.4% risk for pre-sarcopenia in adjusted model (relative risk = 2.094; p = 0.002), respectively. Both asthma (β = 0.100, p = 0.006) and EC (β = 0.023, p = 0.017) exerted significantly casual effects on pre-sarcopenia. However, as for sarcopenia, merely EC exhibited a significantly casual effect (β = 0.005, p = 0.048). Significant casual effects of AD (β = - 0.027, p = 0.003), asthma (β = - 0.029, p = 0.027) and EC (β = - 0.041, p < 0.001) on decreased appendicular lean mass (ALM) were observed using the inverse-variance weighted method and the Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) method. Our results revealed a contributory role of AD, asthma and EC on sarcopenia, especially in terms of decreased ALM, an indicator for sarcopenia diagnosis. The findings of our study will raise the awareness of preventing aging-related disorders or geriatric syndromes among allergic populations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43657-023-00110-4.

Evaluation of the differences between low-salt solid-state fermented soy sauce and high-salt diluted-state fermented soy sauce in China: from taste-active compounds and aroma-active compounds to sensory characteristics

BACKGROUND

The present study aimed to determine the components related to sensory properties in soy sauce and to characterize the differences between low-salt solid-state fermented soy sauce (LSFSS) and high-salt diluted-state fermented soy sauce (HDFSS). The taste and aroma active components of 18 commercially available soy sauces (eight types of LSFSS and 10 types of HDFSS) were characterized. The relationship between these compounds, soy sauce samples, and sensory properties was modeled by partial least squares regression.

RESULTS

The analysis showed that the 11 taste-active components, including glutamic acid, glycine, alanine, threonine, malic acid, citric acid, tartaric acid, acetic acid, lactic acid, reducing sugar and salt, contributed greatly to the taste of soy sauce. In addition, umami, saltiness and sweetness are the characteristic tastes of HDFSS, whereas sourness and bitterness were the characteristic tastes of LSFSS. At the same time, seven aroma-active compounds, namely 4-ethyl-2-methoxyphenol, ethanol, 3-methyl-1-butanol, ethyl acetate, 2-phenethyl alcohol, 3-methyl thiopropanol and 2-ethyl-4-hydroxy-5-methylfuran-3-one, played a decisive role in the flavor of soy sauce. In addition, HDFSS presented the aroma attributes of smoky, alcoholic, floral, fruity and caramel-like, whereas LSFSS mainly presented sour and malty aroma attributes.

CONCLUSION

The present study reveals new insight into the relationship between the chemical composition and sensory characteristics of soy sauce, which is of great significance for developing an objective measurement system and providing a theoretical basis to improve the sensory quality of soy sauce. © 2023 Society of Chemical Industry.

Phase Conductance of BiFeO3 Film

In this work, the local conductance of the tetragonal-like (T-like) and rhombohedral-like (R-like) phases of epitaxial BiFeO3 film is systematically studied via conductive atomic force microscopy. At higher tip voltage, there is a mutual transition between the T-like and R-like phases, which could be attributed to the strain relaxation in the T-like phase induced by electric poling, as well as local polarization switching. The T-like phase exhibits a higher conductance, which is related to the lower interface potential barrier between the tip and film surface. Reversible low- and high-current states in the T-like phase can be tuned by polarization switching. These results will be helpful for designing novel nanoelectronic devices, such as voltage and strain sensors.

Construction of a plasmid-free L-leucine overproducing Escherichia coli strain through reprogramming of the metabolic flux

BACKGROUND

L-Leucine is a high-value amino acid with promising applications in the medicine and feed industries. However, the complex metabolic network and intracellular redox imbalance in fermentative microbes limit their efficient biosynthesis of L-leucine.

RESULTS

In this study, we applied rational metabolic engineering and a dynamic regulation strategy to construct a plasmid-free, non-auxotrophic Escherichia coli strain that overproduces L-leucine. First, the L-leucine biosynthesis pathway was strengthened through multi-step rational metabolic engineering. Then, a cooperative cofactor utilization strategy was designed to ensure redox balance for L-leucine production. Finally, to further improve the L-leucine yield, a toggle switch for dynamically controlling sucAB expression was applied to accurately regulate the tricarboxylic acid cycle and the carbon flux toward L-leucine biosynthesis. Strain LEU27 produced up to 55 g/L of L-leucine, with a yield of 0.23 g/g glucose.

CONCLUSIONS

The combination of strategies can be applied to the development of microbial platforms that produce L-leucine and its derivatives.

A Comparative Study of the Effects of Whole Cereals and Refined Cereals on Intestinal Microbiota

Cereals are one of the most important foods on which human beings rely to sustain basic life activities and are closely related to human health. This study investigated the effects of different steamed buns on intestinal microbiota. Three steamed buns were prepared using refined flour (RF), 1:1 mixed flour (MF), and whole wheat flour (WF). In vitro digestion simulations were conducted using a bionic gastrointestinal reactor (BGR) to examine their influence on intestinal microbiota. The results showed that at 0.5% addition, butyric acid and short-chain fatty acids in WF were significantly different from those in RF and MF (p < 0.05). WF also promoted the proliferation of beneficial microbiota, such as Megamonas and Subdoligranulum. At 0.5%, 1.0%, and 1.5% additions of WF, acetic acid and short-chain fatty acids at 1.5% WF increased by 1167.5% and 11.4% from 0.5% WF, respectively, and by 20.2% and 7.6% from 1.0% WF, respectively. WF also promoted the proliferation of Bifidobacterium, Lactobacillus, and Bacteroides and inhibited the growth of pathogenic microbiota, such as Streptococcus, Enterococcus, and Klebsiella. These findings support the consumption of whole cereals and offer insights into the development of new functional foods derived from wheat.

New two-stage pH combined with dissolved oxygen control strategy for cyclic β-1,2 glucans synthesis

On the basis of a novel two-stage pH combined with dissolved oxygen (DO) control strategy in fed-batch fermentation, this research addresses the influence of pH on cyclic β-1,2-glucans (CβGs) biosynthesis and melanin accumulation during the production of CβGs by Rhizobium radiobacter ATCC 13,333. Under these optimal fermentation conditions, the maximum cell concentration and CβGs concentration in a 7-L stirred-tank fermenter were 7.94 g L^-1 and 3.12 g L^-1, which were the maximum production reported for R. radiobacter. The melanin concentration of the fermentation broth was maintained at a low level, which was beneficial to the subsequent separation and purification of the CβGs. In addition, a neutral extracellular oligosaccharide (COGs-1) purified by the two-stage pH combined with DO control strategy fermentation medium was structurally characterized. Structural analyses indicated that COGs-1 was a family of unbranched cyclic oligosaccharides composed of only β-1,2-linked D-glucopyranose residues with degree of polymerization between 17 and 23, namely CβGs. This research provides a reliable source of CβGs and structural basis for further studies of biological activity and function. KEY POINTS: • A two-stage pH combined with DO control strategy was proposed for CβGs production and melanin biosynthesis by Rhizobium radiobacter. • The final extracellular CβGs production reached 3.12 g L^-1, which was the highest achieved by Rhizobium radiobacter. • The existence of CβGs could be detected by TLC quickly and accurately.

Association of antibiotics use in preschool age with atopic and allergic skin diseases in young adulthood: a population-based retrospective cohort study

BACKGROUND

Overuse and misuse of antibiotics is a public health problem in low-income and middle-income countries. Although the association of antibiotics with atopic and allergic diseases has been established, most studies focused on prenatal exposure and the occurrence of disease in infants or young children.

OBJECTIVE

To investigate the association of preschool use of antibiotics with atopic and allergic skin diseases in young adulthood.

DESIGN

Population-based retrospective cohort.

SETTING AND PARTICIPANTS

The first-year college students (n=20 123) from five universities were investigated. The sampled universities are located in Changsha, Wuhan, Xiamen, Urumqi and Hohhot, respectively.

METHODS

We conducted a dermatological field examination and a questionnaire survey inquiring the participants about the frequency of upper respiratory tract infection (URTI) and the preschool antibiotics use (prior to 7 years old). The two-level probit model was used to estimate the associations, and adjusted risk ratio (aRR) and 95% CI were presented as the effect size.

RESULTS

A total of 20 123 participants with complete information was included in the final analysis. The frequent antibiotics use intravenously (aRR 1.36, 95% CI 1.14 to 1.62) and orally (aRR 1.18, 95% CI 1.01 to 1.38) prior to 7 years old was significantly associated with atopic dermatitis in young adulthood. Similar trends could be observed in allergic skin diseases among those who use antibiotics orally and intravenously, with RRs of 1.16 (95% CI 1.01 to 1.34) and 1.33 (95% CI 1.13 to 1.57), respectively.

CONCLUSIONS

Preschool URTI and antibiotics use significantly increases the risk of atopic and allergic skin diseases in young adulthood.

A label-free, fast and high-specificity technique for plant cell wall imaging and composition analysis

BACKGROUND

New cell wall imaging tools permit direct visualization of the molecular architecture of cell walls and provide detailed chemical information on wall polymers, which will aid efforts to use these polymers in multiple applications; however, detailed imaging and quantification of the native composition and architecture in the cell wall remains challenging.

RESULTS

Here, we describe a label-free imaging technology, coherent Raman scattering (CRS) microscopy, including coherent anti-Stokes Raman scattering (CARS) microscopy and stimulated Raman scattering (SRS) microscopy, which can be used to visualize the major structures and chemical composition of plant cell walls. We outline the major steps of the procedure, including sample preparation, setting the mapping parameters, analysis of spectral data, and image generation. Applying this rapid approach will help researchers understand the highly heterogeneous structures and organization of plant cell walls.

CONCLUSIONS

This method can potentially be incorporated into label-free microanalyses of plant cell wall chemical composition based on the in situ vibrations of molecules.

N6-methyldeoxyadenine and histone methylation mediate transgenerational survival advantages induced by hormetic heat stress

Environmental stress can induce survival advantages that are passed down to multiple generations, representing an evolutionarily advantageous adaptation at the species level. Using the nematode worm Caenorhabditis elegans as a model, we found that heat shock experienced in either parent could increase the longevity of themselves and up to the fifth generation of descendants. Mechanistic analyses revealed that transcription factor DAF-16/FOXO, heat shock factor HSF-1, and nuclear receptor DAF-12/FXR functioned transgenerationally to implement the hormetic stress response. Histone H3K9me3 methyltransferases SET-25 and SET-32 and DNA N6-methyl methyltransferase DAMT-1 participated in transmitting high-temperature memory across generations. H3K9me3 and N6-methyladenine could mark heat stress response genes and promote their transcription in progeny to extend life span. We dissected the mechanisms responsible for implementing and transmitting environmental memories in descendants from heat-shocked parents and demonstrated that hormetic stress caused survival benefits could be transmitted to multiple generations through H3K9me3 and N6-mA modifications.

Grazing offsets the stimulating effects of nitrogen addition on soil CH4 emissions in a meadow steppe in Northeast China

Grazing is the most common land use type for grasslands, and grazing may alter the impacts of the predicted enhancement of nitrogen deposition on soil CH4 flux. To understand the effects of nitrogen addition, grazing, and their interactions on soil CH4 flux, we conducted a field study on CH4 flux in a meadow steppe in Northeast China from 2017 to 2018. We measured the soil CH4 flux and soil physiochemical and vegetation parameters. The studied meadow steppe soil acted as a CH4 source due to the legacy effects of an extreme rainfall event. During the experimental period, the average CH4 fluxes were 7.8 ± 1.0, 5.8 ± 0.5, 9.3 ± 0.9 and 7.6 ± 0.6 μg m-2 h-1 for the CK (control), G (grazing), N (nitrogen addition) and NG (grazing and nitrogen addition) treatments, respectively. The cumulative CH4 fluxes were 24.9 ± 2.6, 11.5 ± 4.9, 28.8 ± 4.2 and 17.8 ± 3.5 μg m-2 yr-1 for the CK, G, N and NG treatments, respectively. The N addition increased the average CH4 flux by 19%, and the grazing treatment reduced it by 25%. The soil CH4 flux was positively correlated with the 0-10 cm soil water filled pore space (P < 0.01), soil NH4+-N (P < 0.01) and soil NO3--N (P < 0.01), but negatively correlated with the 0-10 cm soil temperature (P < 0.01), except for the sampling dates that were strongly influenced by the extreme rainfall event. The average CH4 flux was significantly (P < 0.05) affected by the grazing and N addition treatments with the N addition treatment significantly (P < 0.05) increased the CH4 flux, whereas grazing significantly (P < 0.05) decreased the CH4 flux. Grazing offset the stimulating effects of N addition on CH4 flux, and there was no difference (P = 0.79) in the CH4 flux between the CK and NG plots. In summary, moderate grazing has the potential to reduce the negative impacts of N addition on CH4 flux and can increase the capacity of the soil CH4 sink in the studied meadow steppe.

Effect of soil aeration on root morphology and photosynthetic characteristics of potted tomato plants (Solanum lycopersicum) at different NaCl salinity levels

BACKGROUND

Salt stress is one of the environmental factors that greatly limits crop production worldwide because high salt concentrations in the soil affect morphological responses and physiological and metabolic processes, including root morphology and photosynthetic characteristics. Soil aeration has been reported to accelerate the growth of plants and increase crop yield. The objective of this study was to examine the effects of 3 NaCl salinity levels (28, 74 and 120 mM) and 3 aeration volume levels (2.3, 4.6 and 7.0 L/pot) versus non-aeration and salinity treatments on the root morphology, photosynthetic characteristics and chlorophyll content of potted tomato plants.

RESULTS

The results showed that both aeration volume and salinity level affected the root parameters, photosynthetic characteristics and chlorophyll content of potted tomato plants. The total length, surface area and volume of roots increased with the increase in aeration volume under each NaCl stress level. The effect was more marked in the fine roots (especially in ≤1 mm diameter roots). Under each NaCl stress level, the photosynthetic rate and chlorophyll content of tomato significantly increased in response to the aeration treatments. The net photosynthetic rate and chlorophyll a and t content increased by 39.6, 26.9, and 17.9%, respectively, at 7.0 L/pot aeration volume compared with no aeration in the 28 mM NaCl treatment. We also found that aeration could reduce the death rate of potted tomato plants under high salinity stress conditions (120 mM NaCl).

CONCLUSIONS

The results suggest that the negative effect of NaCl stress can be offset by soil aeration. Soil aeration can promote root growth and increase the photosynthetic rate and chlorophyll content, thus promoting plant growth and reducing the plant death rate under NaCl stress conditions.

Sequencing flow-sorted short arm of Haynaldia villosa chromosome 4V provides insights into its molecular structure and virtual gene order

BACKGROUND

Haynaldia villosa (H. villosa) has been recognized as a species potentially useful for wheat improvement. The availability of its genomic sequences will boost its research and application.

RESULTS

In this work, the short arm of H. villosa chromosome 4V (4VS) was sorted by flow cytometry and sequenced using Illumina platform. About 170.6 Mb assembled sequences were obtained. Further analysis showed that repetitive elements accounted for about 64.6% of 4VS, while the coding fraction, which is corresponding to 1977 annotated genes, represented 1.5% of the arm. The syntenic regions of the 4VS were searched and identified on wheat group 4 chromosomes 4AL, 4BS, 4DS, Brachypodium chromosomes 1 and 4, rice chromosomes 3 and 11, and sorghum chromosomes 1, 5 and 8. Based on genome-zipper analysis, a virtual gene order comprising 735 gene loci on 4VS genome was built by referring to the Brachypodium genome, which was relatively consistent with the scaffold order determined for Ae. tauschii chromosome 4D. The homologous alleles of several cloned genes on wheat group 4 chromosomes including Rht-1 gene were identified.

CONCLUSIONS

The sequences provided valuable information for mapping and positional-cloning genes located on 4VS, such as the wheat yellow mosaic virus resistance gene Wss1. The work on 4VS provided detailed insights into the genome of H. villosa, and may also serve as a model for sequencing the remaining parts of H. villosa genome.

Two members of TaRLK family confer powdery mildew resistance in common wheat

BACKGROUND

Powdery mildew, caused by Blumeria graminearum f.sp. tritici (Bgt), is one of the most severe fungal diseases of wheat. The exploration and utilization of new gene resources is the most effective approach for the powdery mildew control.

RESULTS

We report the cloning and functional analysis of two wheat LRR-RLKs from T. aestivum c.v. Prins- T. timopheevii introgression line IGV1-465, named TaRLK1 and TaRLK2, which play positive roles in regulating powdery mildew resistance in wheat. The two LRR-RLKs contain an ORF of 3,045 nucleotides, encoding a peptide of 1014 amino acids, with seven amino acids difference. Their predicted proteins possess a signal peptide, several LRRs, a trans-membrane domain, and a Ser/Thr protein kinase domain. In response to Bgt infection, the TaRLK1/2 expression is up-regulated in a developmental-stage-dependent manner. Single-cell transient over-expression and gene-silencing assays indicate that both genes positively regulate the resistance to mixed Bgt inoculums. Transgenic lines over-expressing TaRLK1 or TaRLK2 in a moderate powdery mildew susceptible wheat variety Yangmai 158 led to significantly enhanced powdery mildew resistance. Exogenous applied salicylic acid (SA) or hydrogen peroxide (H2O2) induced the expression of both genes, and H2O2 had a higher accumulation at the Bgt penetration sites in RLK over-expression transgenic plants, suggesting a possible involvement of SA and altered ROS homeostasis in the defense response to Bgt infection. The two LRR-RLKs are located in the long arm of wheat chromosome 2B, in which the powdery mildew resistance gene Pm6 is located, but in different regions.

CONCLUSIONS

Two members of TaRLK family were cloned from IGV1-465. TaRLK1 and TaRLK2 contribute to powdery mildew resistance of wheat, providing new resistance gene resources for wheat breeding.