Advances in biotin biosynthesis and biotechnological production in microorganisms.

Biotin, also known as vitamin H or B7, acts as a crucial cofactor in the central metabolism processes of fatty acids, amino acids, and carbohydrates. Biotin has important applications in food additives, biomedicine, and other fields. While the ability to synthesize biotin de novo is confined to microorganisms and plants, humans and animals require substantial daily intake, primarily through dietary sources and intestinal microflora. Currently, chemical synthesis stands as the primary method for commercial biotin production, although microbial biotin production offers an environmentally sustainable alternative with promising prospects. This review presents a comprehensive overview of the pathways involved in de novo biotin synthesis in various species of microbes and insights into its regulatory and transport systems. Furthermore, diverse strategies are discussed to improve the biotin production here, including mutation breeding, rational metabolic engineering design, artificial genetic modification, and process optimization. The review also presents the potential strategies for addressing current challenges for industrial-scale bioproduction of biotin in the future. This review is very helpful for exploring efficient and sustainable strategies for large-scale biotin production.

Potential immune evasion of the severe acute respiratory syndrome coronavirus 2 Omicron variants.

Coronavirus disease 2019 (COVID-19), which is caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused a global pandemic. The Omicron variant (B.1.1.529) was first discovered in November 2021 in specimens collected from Botswana, South Africa. Omicron has become the dominant variant worldwide, and several sublineages or subvariants have been identified recently. Compared to those of other mutants, the Omicron variant has the most highly expressed amino acid mutations, with almost 60 mutations throughout the genome, most of which are in the spike (S) protein, especially in the receptor-binding domain (RBD). These mutations increase the binding affinity of Omicron variants for the ACE2 receptor, and Omicron variants may also lead to immune escape. Despite causing milder symptoms, epidemiological evidence suggests that Omicron variants have exceptionally higher transmissibility, higher rates of reinfection and greater spread than the prototype strain as well as other preceding variants. Additionally, overwhelming amounts of data suggest that the levels of specific neutralization antibodies against Omicron variants decrease in most vaccinated populations, although CD4+ and CD8+ T-cell responses are maintained. Therefore, the mechanisms underlying Omicron variant evasion are still unclear. In this review, we surveyed the current epidemic status and potential immune escape mechanisms of Omicron variants. Especially, we focused on the potential roles of viral epitope mutations, antigenic drift, hybrid immunity, and "original antigenic sin" in mediating immune evasion. These insights might supply more valuable concise information for us to understand the spreading of Omicron variants.

Parabens promotes invasive properties of multiple human cells: A potential cancer-associated adverse outcome pathway.

Parabens are esters of p-hydroxybenzoic acid, which have been used as preservatives and considered safe for nearly a century, until the last two decades when concerns began to be raised about their association with cancers. Knowledge of the mode of action of parabens on the metastatic properties of different cancer cells is still very limited. In the present study, we investigated the effects of methylparaben (MP) and propylparaben (PP) on cell invasion and/or migration in multiple human cancerous and noncancerous cells, including hepatocellular carcinoma cells (HepG2), cervical carcinoma cells (HeLa), breast carcinoma cells (MCF-7), and human placental trophoblasts (HTR-8/SVneo). MP and PP at concentrations in a range of 5-500 µg/L significantly promoted the invasion of four cell lines, with a minimum effective concentration of 5 µg/L. MP and PP up-regulated the expression levels and enzymatic activities of matrix metalloproteinase 2 and 9 (MMP2 and MMP9), as well as altered the expression of the tissue inhibitors of metalloproteinase 1 and 2 (TIMP1 and TIMP2) in four cell lines, suggesting MMPs/TIMPs as potential key events (KEs) for paraben-induced cell invasion. Activation of the p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal protein kinases 1/2 (JNK1/2) signaling pathways was required for MP- and PP-promoted invasion of four cell lines, suggesting MAPK signaling pathways as candidates for KEs in cancer or noncancerous cells response to paraben exposure. This study showed for the first time that the two widely used parabens, MP and PP, promoted invasive capacity of multiple human cells through a common mode of action. This study provides evidence for the establishment of a potential cancer-associated AOP for parabens based on pathway-specific mechanism(s), which contributes towards assessing the health risks of these environmental chemicals.

Universal Strategy for Metal-Organic Framework Growth: From Cascading-Functional Films to MOF-on-MOFs.

Transformation of metal-organic framework (MOF) particles into thin films is urgently needed for the persistent development of well-applicable devices, and recently emerging functional-integrated hybrid frameworks. Although some flexible polymers and exclusive modification approaches have been proposed, the additive-free and widely applicable strategy has not been reported, hampering the deep investigation of the structure-performance relationship. A universal strategy for the in situ growth of large-area and continuous MOF films with controllable microstructures is introduced, through the modification of multi-scale and multi-structure substrates with poly(4-vinylpyridine) as the anchor to capture metal ions via Coulomb attraction. Based on the clarified structure-adsorption-separation mechanisms, the customized devices fabricated by in situ growth can achieve highly selective adsorption and excellently synergetic separation of various industrially relevant isomers. In addition, this strategy is also feasible for the construction of MOF-on-MOFs with varied lattice parameters. This strategy is easy to implement and will be widely applicable to the surface growth of diverse MOFs on desired substrates, and provides a new concept for developing hybrid MOFs integrating with customized functionalities.

L-arginine metabolism ameliorates age-related cognitive impairment by Amuc_1100-mediated gut homeostasis maintaining.

Aging-induced cognitive impairment is associated with a loss of metabolic homeostasis and plasticity. An emerging idea is that targeting key metabolites is sufficient to impact the function of other organisms. Therefore, more metabolism-targeted therapeutic intervention is needed to improve cognitive impairment. We first conducted untargeted metabolomic analyses and 16S rRNA to identify the aging-associated metabolic adaption and intestinal microbiome change. Untargeted metabolomic analyses of plasma revealed L-arginine metabolic homeostasis was altered during the aging process. Impaired L-arginine metabolic homeostasis was associated with low abundance of intestinal Akkermansia muciniphila (AKK) colonization in mice. Long-term supplementation of AKK outer membranes protein-Amuc_1100, rescued the L-arginine level and restored cognitive impairment in aging mice. Mechanically, Amuc_1100 acted directly as a source of L-arginine and enriched the L-arginine-producing bacteria. In aged brain, Amuc_1100 promoted the superoxide dismutase to alleviated oxidation stress, and increased nitric oxide, derivatives of L-arginine, to improve synaptic plasticity. Meanwhile, L-arginine repaired lipopolysaccharide-induced intestinal barrier damage and promoted growth of colon organoid. Our findings indicated that aging-related cognitive impairment was closely associated with the disorders of L-arginine metabolism. AKK-derived Amuc_1100, as a potential postbiotic, targeting the L-arginine metabolism, might provide a promising therapeutic strategy to maintain the intestinal homeostasis and cognitive function in aging.

Nanoscale-controlled organicinorganic hybrid spheres for comprehensive enrichment of ultratrace chlorobenzenes in marine and fresh water.

The size of the adsorbent has the potential to influence extraction performance, but the size effect at the nanoscale is still poorly understood. In this study, organic-inorganic hybrid nanospheres (OIHNs) with controllable nanoscale sizes of 30, 50, and 100 nm were successfully prepared. These materials were further fabricated as solid phase microextraction (SPME) coatings with similar thicknesses, and coupled with gas chromatography-mass spectrometry (GC-MS) to investigate their extraction performance. The results showed that the extraction capacities of OIHNs for chlorobenzenes (CBs) and polycyclic aromatic hydrocarbons (PAHs) were much better than those of their corresponding derived carbon materials, despite the smaller specific surface areas and lower porosities of them. In addition, the enrichment performance increased significantly with decreasing particle size, and the OIHN-30 coating demonstrated the best performance, with enrichment factors ranging from 1098 to 6853 for CBs. Finally, a highly sensitive and practical analytical method was established with a wide linear range of 0.5-5000 ng·L-1, and the limits of quantification (LOQs) were 0.43-1.7 ng·L-1. The determinations of ultratrace CBs in five marine water samples and five fresh water samples were realized successfully. This study is expected to contribute to a deep understanding of the environmental effects of nanoparticles and the design of high-performance adsorbents.

Heat-inactivated Bifidobacterium adolescentis ameliorates colon senescence through Paneth-like-cell-mediated stem cell activation.

Declined numbers and weakened functions of intestinal stem cells (ISCs) impair the integrity of the intestinal epithelium during aging. However, the impact of intestinal microbiota on ISCs in this process is unclear. Here, using premature aging mice (telomerase RNA component knockout, Terc-/-), natural aging mice, and in vitro colonoid models, we explore how heat-inactivated Bifidobacterium adolescentis (B. adolescentis) affects colon senescence. We find that B. adolescentis could mitigate colonic senescence-related changes by enhancing intestinal integrity and stimulating the regeneration of Lgr5+ ISCs via Wnt/ß-catenin signaling. Furthermore, we uncover the involvement of Paneth-like cells (PLCs) within the colonic stem-cell-supporting niche in the B. adolescentis-induced ISC regeneration. In addition, we identify soluble polysaccharides (SPS) as potential effective components of B. adolescentis. Overall, our findings reveal the role of heat-inactivated B. adolescentis in maintaining the ISCs regeneration and intestinal barrier, and propose a microbiota target for ameliorating colon senescence.

Melamine-participant hydrogen-bonded organic frameworks with strong hydrogen bonds and hierarchical micropores driving extraction of nitroaromatic compounds.

Enrichment and detection of trace pollutants in the real matrix are essential for evaluating water quality. In this study, benefiting from the good affinities of 1,3,6,8-tetra(4-carboxylphenyl)pyrene) (H4TBAPy) with itself and melamine (MA) respectively, the composite hydrogen-bonded organic frameworks (HOFs, MA/PFC-1), PFC-1 self-assembled by 1,3,6,8-tetra(4-carboxylphenyl)pyrene), were successfully constructed by the mild strategy of solvent evaporation at room temperature. Through a series of characterizations, such as Fourier transform infrared spectra, X-ray diffraction, thermal gravimetric analyses, and N2 adsorption-desorption, etc., the MA/PFC-1 was confirmed to be a stable and excellent material. In addition, it possessed high surface area, hierarchical micropores, strong hydrogen bonds, and rich function groups containing N and O heteroatoms, since the newly introduced MA could be another hydrogen bonding motif, as well as increased the polarity of reaction solvent. These advantages make MA/PFC-1 be an ideal coating material for solid phase microextraction (SPME). Satisfactory enrichment factors for nitroaromatic compounds (NACs) were got by the MA/PFC-1 fiber under the optimized conditions obtained by the control variables (extraction time of 60 min, extraction temperature of 80 °C, desorption time of 6 min, desorption temperature of 260 °C, pH value of 7, and stirring speed of 250 rpm). MA/PFC-1 was further used to develop an analytical method for NACs based on head-space SPME coupled with gas chromatography‒mass spectrometry (GC‒MS). The developed method with low limits of detection (4.30-20.83 ng L-1) and good reproducibility (relative standard deviations <8.6%). The excellent performance allowed the successful application of the developed method in the determinations of trace NACs in real water samples with recoveries of 80.1%-119%. This study proposed a mild approach to synthesize composite HOFs via doping MA and developed an environmentally friendly method for the precise determinations of NACs in the environment.

Cognition about emergency management of avulsed incisor in children among dentists in Guangdong province.

OBJECTIVES: This study aimed to evaluate and analyze the current situation of dentists in Guangdong pro-vince regarding the management of avulsed incisors, thereby providing a reference for making treatment strategies for avulsed incisors in the future. METHODS: A total of 712 dentists with different educational backgrounds and working conditions in Guangdong province were randomly selected to conduct an online questionnaire survey on the cognition of children with avulsed incisors from April 2022 to May 2022. The data were recorded by Excel software and statistics were analyzed on Stata/SE 15.1. RESULTS: A total of 712 dentists were investigated and 701 questionnaires were collected (98.46%). In addition, 65.9% of investigators came from the Department of Stomatology in a First-class Hospital or Stomatological Hospital. The results showed that the average number of avulsed teeth consulted by dentists was less than 20 per year. Although 99.7% of respondents considered normal saline as a suitable storage medium, 3.1% and 23.8% of them had a misunderstanding that the tap/alcohol could be used for root cleaning. Moreover, 93.4% was the correct selection rate of the treatment plan for processing on root surfaces before replanting by investigators. The correct selection rate of the duration using elastic fixation was only 10.7%. Meanwhile, 42.9% of investigators refused to inoculate tetanus immunoglobulin after teeth replanting. Emergency management of dental avulsion (EM) and clinical management of dental avulsion (CM) answered correctly with average scores of 14.60±11.85 and 14.48±2.67, respectively. Multivariate linear regression analysis revealed that working years were negatively correlated with EM and CM scores (P<0.05). There was a positive correlation between CM and EM scores with the number of avulsion cases treated by physicians each year (P<0.05). In terms of the EM score of dentists' learning attitude, investigators who had received enough knowledge were higher than those who had not and insufficient knowledge reserved, and the difference was statistically significant (P<0.05). The scores of investigators who thought they had a certain degree of knowledge about dental trauma were higher than those who thought they "did not understand", and the difference was statistically significant (P<0.05). In terms of CM scores, investigators who thought the knowledge of dental trauma was "very helpful" had higher scores than those who thought it was "not helpful", and the difference was statistically significant (P<0.05). The scores of the investigators who thought they had "relatively sufficient knowledge" of dental trauma were higher than those who thought they had "no knowledge" or "insufficient know-ledge", and the difference was statistically significant (P<0.05). CONCLUSIONS: The overall accuracy of the management of avulsed incisors among dentists was low in Guangdong province. Dentists were more likely to have a higher rate of accuracy choice in treatment options for luxation injury and avulsion to enhance the prognosis of replanted teeth.

A robust and ultra-high-surface hydrogen-bonded organic framework promoting high-efficiency solid phase microextraction of multiple persistent organic pollutants from beverage and tea.

Persistent organic pollutants (POPs) are widely distributed in the environment and are toxic, even at low concentrations. In this study, we first used hydrogen-bonded organic framework (HOF) to enrich POPs, based on solid phase microextraction (SPME). The HOF called PFC-1 (self-assembled by 1,3,6,8-tetra(4-carboxylphenyl)pyrene) has an ultra-high specific surface area, excellent thermochemical stability, and abundant functional groups, making it potential to be an excellent coating in SPME. And the as-prepared PFC-1 fiber have demonstrated outstanding enrichment abilities for nitroaromatic compounds (NACs) and POPs. Furthermore, the PFC-1 fiber was coupled with gas chromatography-mass spectrometry (GC-MS) to develop an ultrasensitive and practical analytical method with wide linearity (0.2-200 ng·L-1), low detection limits for organochlorine pesticides (OCPs) (0.070-0.082 ng·L-1) and polychlorinated biphenyls (PCBs) (0.030-0.084 ng·L-1), good repeatability (6.7-9.9%), and satisfactory reproducibility (4.1-8.2%). Trace concentrations of OCPs and PCBs in drinking water, tea beverage, and tea were also determined precisely with the proposed analytical method.

Exposure to bisphenols, parabens and phthalates during pregnancy and postpartum anxiety and depression symptoms: Evidence from women with twin pregnancies.

BACKGROUND: Women are vulnerable to suffer from the common mental disorders like anxiety and depression during the postpartum period. Exposure to bisphenols, parabens, and phthalates has been linked to anxiety and depression symptoms in the general population. However, little is known about their impacts on postpartum women. OBJECTIVE: To evaluate the effects of individual and joint exposure to 11 nonpersistent chemicals during pregnancy on postpartum anxiety and depression. METHODS: Among 278 mothers from the Wuhan Twin Birth Cohort (WTBC), bisphenols, parabens, and phthalate metabolites were measured in maternal urine samples from each trimester. Self-rating Anxiety Scale (SAS) and Edinburgh Postnatal Depression Scale (EPDS) were administrated at early pregnancy and 1 month and 6 months postpartum to determine anxiety and depression symptoms, respectively. Associations between urinary chemical biomarkers (individual or mixtures) and anxiety and depression symptoms were estimated using multiple informant model and quantile-based g-computation. RESULTS: With adjustment for confounders, one quartile increase in the overall chemical mixture (bisphenols, parabens and phthalate metabolites) during the second trimester was associated with 1.03-point (95% CI: 0.07, 1.99, P = 0.036) higher EPDS score at 1 month postpartum, in which bisphenol A (BPA) and bisphenol F (BPF) contributed the most to the positive association. Consistent effects were also observed in the multiple informant models. We found that second-trimester BPA and BPF exposure individually showed the strongest and significant associations with anxiety and depression symptoms, and some of associations differed across trimesters (Ptrimester-int < 0.05). CONCLUSIONS: Second-trimester nonpersistent chemical exposure was associated with increased postpartum anxiety and depression symptoms.

Customized oxygen-rich biochar with ultrahigh microporosity for ideal solid phase microextraction of substituted benzenes.

The synergistic effect of high microporosity and abundant heteroatoms is important for improving the performance of biochar in various fields. However, it is still challenging to create enough micropores for biochar, while simultaneously retaining the heteroatoms from biomass. A series of biochar with variable microstructures was successfully prepared by carbonization and following ball milling on lotus pedicel (LP), watermelon rind (WR), and litchi rind (LR). The pore structures and heteroatoms of biochar were characterized in detail. Notably, high microporosity could be realized by the carbonization of LR, and further ball milling resulted in a higher microporous surface area (1323.4 m2·g-1) and richer oxygen. Furthermore, the obtained biochar was fabricated as solid phase microextraction (SPME) coatings with uniform morphologies and similar thicknesses to deeply investigate the relationships between the microstructures and extraction performance. The best performance was demonstrated by the LR800BM, with enrichment factors from 1780 to 155,217. Finally, it was coupled with gas chromatography-mass spectrometry (GC-MS) to develop an analytical method with a wide linear range (1-50,000 ng·L-1), low limits of detection (0.10-1.4 ng·L-1), good repeatability (0.83 %-7.5 %) and reproducibility (4.2 %-8.9 %). This work provides valuable insights into the structure-performance relationship of biochar, which is important for the design of high-performance biochar-based adsorbents and their applications in the environment.

Host-Guest Encapsulation to Promote the Formation of a Multicomponent Trigonal-Prismatic Metallacage.

An inclusion complex of a trigonal-prismatic metallacage with two coronene guests was constructed by multicomponent coordination-driven self-assembly from a 90° platinum(II) acceptor [cis-Pt(PEt3)2(OTf)2], disodium terephthalate, and 2,4,6-tri(4-pyridyl)-1,3,5-triazine in the presence of excess coronene. This platinum(II)-based trigonal prism was found to be a highly matched host to simultaneously encapsulate two coronene molecules. The encapsulation of coronene can effectively promote the formation of a pure single-prismatic metallacage and can stabilize the self-assembled structure via strong π-π-stacking interactions between coronene and the metallacage.

Lactobacillus johnsonii alleviates colitis by TLR1/2-STAT3 mediated CD206+ macrophagesIL-10 activation.

Imbalance of gut microbiota homeostasis is related to the occurrence of ulcerative colitis (UC), and probiotics are thought to modulate immune microenvironment and repair barrier function. Here, in order to reveal the interaction between UC and gut microbiota, we screened a new probiotic strain by 16S rRNA sequencing from Dextran Sulfate Sodium (DSS)-induced colitis mice, and explored the mechanism and clinical relevance. Lactobacillus johnsonii (L. johnsonii), as a potential anti-inflammatory bacterium was decreased colonization in colitis mice. Gavage L. johnsonii could alleviate colitis by specifically increasing the proportion of intestinal macrophages and the secretion of Il-10 with macrophages depleted model and in Il10-/- mice. We identified this subset of immune cells activated by L. johnsonii as CD206+ macrophagesIL-10. Mechanistically, L. johnsonii supplementation enhanced the mobilization of CD206+ macrophagesIL-10 through the activation of STAT3 in vivo and in vitro. In addition, we revealed that TLR1/2 was essential for the activation of STAT3 and the recognition of L. johnsonii by macrophages. Clinically, there was positive correlation between the abundance of L. johnsonii and the expression level of MRC1, IL10 and TLR1/2 in UC tissues. L. johnsonii could activate native macrophages into CD206+ macrophages and release IL-10 through TLR1/2-STAT3 pathway to relieve experimental colitis. L. johnsonii may serve as an immunomodulator and anti-inflammatory therapeutic target for UC.

Tuning the Solvent Alkyl Chain to Tailor Electrolyte Solvation for Stable Li-Metal Batteries.

1,2-Dimethoxyethane (DME) has been considered as the most promising electrolyte solvent for Li-metal batteries (LMBs). However, challenges arise from insufficient Li Coulombic efficiency (CE) and poor anodic stability associated with DME-based electrolytes. Here, we proposed a rational molecular design methodology to tailor electrolyte solvation for stable LMBs, where shortening the middle alkyl chain of the solvent could reduce the chelation ability, while increasing the terminal alkyl chain of the solvent could increase the steric hindrance, affording a diethoxymethane (DEM) solvent with ultra-weak solvation ability. When serving as a single solvent for electrolyte, a peculiar solvation structure dominated by contact ion pairs (CIPs) and aggregates (AGGs) was achieved even at a regular salt concentration of 1 m, which gives rise to anion-derived interfacial chemistry. This illustrates an unprecedentedly high Li||Cu CE of 99.1% for a single-salt single-solvent (non-fluorinated) electrolyte at ∼1 m. Moreover, this 1 m DEM-based electrolyte also remarkably suppresses the anodic dissolution of Al current collectors and significantly improves the cycling performance of high-voltage cathodes. This work opens up new frontiers in engineering electrolytes toward stable LMBs with high energy densities.

High-surface ß-Ketoenamine linked covalent organic framework driving broad-spectrum solid phase microextraction on multi-polar aromatic esters.

Aromatic esters have been widely used in daily life with non-ignorable dangers, such as plasticizer, flavor, and preservative. Their wide applications and corresponding hazards caused by overuse have promoted the rapid development of sensitively analytical method for effective regulation. However, the variety makes it challenging for broad-spectrum and simultaneous extraction of diverse aromatic esters from the highly complex cosmetic samples. To our delight, a covalent organic framework, named DaTp (1, 3, 5-triformylphloroglucinol-2, 6-diaminoanthracene), possessing high specific surface, excellently thermochemical stability, and abundant electron-rich heteroatoms, has been synthesized and fabricated as a competitive solid phase microextraction coating for extracting the trace analytes with diverse polarity, through the hydrophobic interaction, π-π conjugation and hydrogen bond. Herein, this self-made SPME fiber has been further coupled with gas chromatography-tandem mass spectrometry (GC-MS) to determine the multi-polar aromatic esters in cosmetics packaged with plastic. This developed analytical method showed wide liner ranges, low limits of detection, good repeatability and reproducibility. Finally, the aromatic esters in four cosmetic samples were quantified precisely with satisfactory recoveries (80.7%-118%).

New insights into the role of marine plastic-gels in microplastic transfer from water to the atmosphere via bubble bursting.

The pervasiveness of microplastics (MPs) in global oceans is raising concerns about their adverse impacts on ecosystems. The mechanistic understanding of MP transport is critical for evaluating its fate, flux, and ecological risks specifically. Currently, bubble bursting is believed to represent an important route for MP transfer from sea surfaces to the atmosphere. However, the detailed mechanisms of the complex physico-chemical interactions between MPs, water composition, and gel particles in the air-sea interface remain unknown. Our results suggested three steps for MP transfer between air-sea phases: (1) MPs incorporating into gel aggregates in the water column; (2) further accumulation of plastic-gel aggregate in the surface layer phase; finally (3) ejection of aggregates from the sea when bubbles of trapped air rise to the surface and burst. The water composition (e.g., high salinity, gel concentration and viscosity) can modulate plastic-gel aggregation and subsequent transport from water to the atmosphere. The possible mechanism may be closely tied to the formation of plastic-gel via cation-linking bridges, thereby enhancing plastic-gel ejection into air. Collectively, this work offers unique insights into the role of marine plastic-gels in determining MP fate and transport, especially at air-sea interfaces. The data also provide a better understanding of the corresponding mechanism that may explain the fates of missing plastics in the ocean.

Tuning the Metal Ions of Prussian Blue Analogues in Separators to Enable High-Power Lithium Metal Batteries.

The Li dendrite issue is the major barrier that limits the implement of Li metal anode practically, especially at high current density. From the perspective of the nucleation and growth mechanism of the Li dendrite, we rationally develop a novel Prussian blue analogues (PBA)-derived separator, where tuning the metal ions bestows the PBAs with open metal site to confine anion movement and thereby afford a high Li+ transference number (0.78), and PBA with ordered micropores could act as an ionic sieve to selectively extract Li+ and thereby homogenize Li+ flux. This demonstrates a highly reversible Li plating/stripping cycling for 3000 h at a practically high current density (5.0 mA cm-2). Consequently, a high loading Li||LiFeO4 battery (∼10.0 mg cm-2) demonstrates ultralong cycling life at high current densities (∼5.1 mA cm-2). This work highlights the prospect of optimizing PBAs in regulating ion transport behavior to enable high-power Li metal batteries.

Enhancing regioselectivity of sucrose phosphorylase by loop engineering for glycosylation of L-ascorbic acid.

Sucrose phosphorylase (SPase) has a remarkable capacity to synthesize numerous glucosides from abundantly available sucrose under mild conditions but suffers from specificity and regioselectivity issues. In this study, a loop engineering strategy was introduced to enhance the regioselectivity and substrate specificity of SPase for the efficient synthesis of 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) via L-ascorbic acid (L-AA). P134, L341, and L343 were identified as "hotspots" for modulating the flexibility of loops, which significantly influenced the H-bonding network of L-AA in the active site, as well as the entrance of the substrate channel, thereby altering the regioselectivity and substrate specificity. Finally, the mutant L341V/L343F, with near-perfect control of the selectivity synthesis of the 2-OH group of L-AA (> 99%), was obtained. The AA-2G production by the mutant reached 244 g L-1 in a whole-cell biotransformation system, and the conversion rate of L-AA reached 64%, which is the highest level reported to date. Our work also provides a successful loop engineering case for modulating the regioselectivity and specificity of sucrose phosphorylase. KEY POINTS: • "Hotspots" were identified in the flexible loops of sucrose phosphorylase. • Mutants exhibited improved regioselectivity and specificity against L-ascorbic acid. • Synthesized AA-2G with high yield and regioselectivity by whole-cell of mutant.

Identification of Process-Related Impurities and Corresponding Control Strategy in Biocatalytic Production of 2-O-α-d-Glucopyranosyl-l-ascorbic Acid Using Sucrose Phosphorylase.

2-O-α-d-Glucopyranosyl-l-ascorbic acid (AA-2G) is an ideal substitute for l-ascorbic acid because of its remarkable stability and improved biological activity, which can be easily applied in cosmetic, food, and medicine fields. However, impurity identification and control are significant procedures during the manufacturing of AA-2G. This study assessed a manufacturing routine of AA-2G synthesized by sucrose phosphorylase (SPase). First, three unknown process-related impurities were observed, which were further identified as 3-O-α-d-glucopyranosyl- l-ascorbic acid (impurity I), 2-O-α-d-glucopyranosyl-l-dehydroascorbic acid (impurity II), and 13-O-α-d-glucopyranosyl-2-O-α-d-glucopyranosyl-l-ascorbic acid (impurity III), respectively. Second, a comprehensive formation pathway of impurities was elucidated, and specific strategies corresponding to controlling each impurity were also proposed. Specifically, the content of impurity I can be reduced by 50% by fine tuning reaction conditions. The impurity II-free purification process was also achieved by applying a low concentration of alkali. Finally, a semi-rational design was introduced, and a single mutant L343F was obtained by site-directed mutagenesis, which reduced impurities I and III by 63.9 and 100%, respectively, without affecting the transglycosylation activity. It is expected that the reported impurity identification and control strategies during the AA-2G production will facilitate its industrial production.