Development of fluorescence-linked immunosorbent assay for rapid detection of Staphylococcus aureus

Staphylococcus aureus is a major pathogen that causes infections and life-threatening diseases. Although antibiotics, such as methicillin, have been used, methicillin-resistant S. aureus (MRSA) causes high morbidity and mortality rates, and conventional detection methods are difficult to be used because of time-consuming process. To control the spread of S. aureus, a development of a rapid and simple detection method is required. In this study, we generated a fluorescent anti-S. aureus antibody, and established a novel fluorescence-linked immunosorbent assay (FLISA)-based S. aureus detection method. The method showed high sensitivity and low limit of detection toward MRSA detection. The assay time for FLISA was 5 h, which was faster than that of conventional enzyme-linked immunosorbent assay (ELISA) or rapid ELISA. Moreover, the FLISA-based detection method was applied to diagnose clinically isolated MRSA samples that required only 5.3 h of preincubation. The FLISA method developed in this study can be widely applied as a useful tool for convenient S. aureus detection. KEY POINTS: • A fluorescence-linked immunosorbent assay-based S. aureus detection method • Simultaneous quantification of a maximum of 96 samples within 5 h • Application of the novel system to diagnosis clinical isolates.

Enhancing the soluble expression of α-1,2-fucosyltransferase in E. coli using high-throughput flow cytometry screening coupled with a split-GFP

2'-Fucosyllactose (2'-FL), one of the major human milk oligosaccharides, was produced in several engineered microorganisms. However, the low solubility of α-1,2-fucosyltransferase (α1,2-FucT) often becomes a bottleneck to produce maximum amount of 2'-FL in the microorganisms. To overcome this solubility issue, the following studies were conducted to improve the soluble expression of α1,2-FucT. Initially, hydrophobic amino acids in the hydrophilic region of the 6 α-helices were mutated, adhering to the α-helix rule. Subsequently, gfp11 was fused to the C-terminal of futC gene encoding α1,2-FucT (FutC), enabling selection of high-fluorescence mutants through split-GFP. Each mutant library was screened via fluorescence activated cell sorting (FACS) to separate soluble mutants for high-throughput screening. As a result, L80C single mutant and A121D/P124A/L125R triple mutant were found, and a combined quadruple mutant was created. Furthermore, we combined mutations of conserved sequences (Q150H/C151R/Q239S) of FutC, which showed positive effects in the previous studies from our lab, with the above quadruple mutants (L80C/A121D/P124A/L125R). The resulting strain produced approximately 3.4-fold higher 2'-FL titer than that of the wild-type, suggesting that the conserved sequence mutations are an independent subset of the mutations that further improve the solubility of the target protein acquired by random mutagenesis using split-GFP.

Paintable Decellularized-ECM Hydrogel for Preventing Cardiac Tissue Damage

The tissue-specific heart decellularized extracellular matrix (hdECM) demonstrates a variety of therapeutic advantages, including fibrosis reduction and angiogenesis. Consequently, recent research for myocardial infarction (MI) therapy has utilized hdECM with various delivery techniques, such as injection or patch implantation. In this study, a novel approach for hdECM delivery using a wet adhesive paintable hydrogel is proposed. The hdECM-containing paintable hydrogel (pdHA_t) is simply applied, with no theoretical limit to the size or shape, making it highly beneficial for scale-up. Additionally, pdHA_t exhibits robust adhesion to the epicardium, with a minimal swelling ratio and sufficient adhesion strength for MI treatment when applied to the rat MI model. Moreover, the adhesiveness of pdHA_t can be easily washed off to prevent undesired adhesion with nearby organs, such as the rib cages and lungs, which can result in stenosis. During the 28 days of in vivo analysis, the pdHA_t not only facilitates functional regeneration by reducing ventricular wall thinning but also promotes neo-vascularization in the MI region. In conclusion, the pdHA_t presents a promising strategy for MI treatment and cardiac tissue regeneration, offering the potential for improved patient outcomes and enhanced cardiac function post-MI.

Highly efficient site-specific protein modification using tyrosinase from Streptomyces avermitilis: Structural insight

Tyrosinase-mediated protein conjugation has recently drawn attention as a site-specific protein modification tool under mild conditions. However, the tyrosinases reported to date act only on extremely exposed tyrosine residues, which limits where the target tyrosine can be located. Herein, we report a tyrosinase from Streptomyces avermitilis (SaTYR), that exhibits a much higher activity against tyrosine residues on the protein surface than other tyrosinases. We determined the crystal structure of SaTYR and revealed that the enzyme has a relatively flat and shallow substrate-binding pocket to accommodate a protein substrate. We demonstrated SaTYR-mediated fluorescence dye tagging and PEGylation of a surface tyrosine residue that was unreacted by other tyrosinases with an approximately 95.2 % conjugation yield in 1 h. We also present a structural rationale that considers the steric hindrance from adjacent residues and surrounding structures along with the extent of solvent exposure of residues, as necessary when determining the optimal positions for introducing target tyrosine residues in SaTYR-mediated protein modification. The study demonstrated that the novel tyrosinase, SaTYR, extends the scope of tyrosinase-mediated protein modification, and we propose that site-specific tyrosine conjugation using SaTYR is a promising strategy for protein bioconjugation in various applications.

Single-Walled Carbon Nanotube-Guided Topical Skin Delivery of Tyrosinase to Prevent Photoinduced Damage

When the skin is exposed to ultraviolet radiation (UV), it leads to the degradation of the extracellular matrix (ECM) and results in inflammation. Subsequently, melanocytes are triggered to induce tyrosinase-mediated melanin synthesis, protecting the skin. Here, we introduce a proactive approach to protect the skin from photodamage via the topical delivery of Streptomyces avermitilis-derived tyrosinase (SaTy) using single-walled carbon nanotube (SWNT). Utilizing a reverse electrodialysis (RED) battery, we facilitated the delivery of SaTy-SWNT complexes up to depths of approximately 300 μm, as analyzed by using confocal Raman microscopy. When applied to ex vivo porcine skin and in vivo albino mouse skin, SaTy-SWNT synthesized melanin, resulting in 4-fold greater UV/vis absorption at 475 nm than in mice without SaTy-SWNT. The synthesized melanin efficiently absorbed UV light and alleviated skin inflammation. In addition, the densification of dermal collagen, achieved through SaTy-mediated cross-linking, reduced photoinduced wrinkles by 66.3% in the affected area. Our findings suggest that SWNT-mediated topical protein delivery holds promise in tissue engineering applications.

Generation of a novel monoclonal antibody against inflammatory biomarker S100A8 using hybridoma technology

OBJECTIVES

S100A8 is highly expressed in several inflammatory and oncological conditions. To address the current lack of a reliable and sensitive detection method for S100A8, we generated a monoclonal antibody with a high binding affinity to human S100A8 to enable early disease diagnosis.

RESULTS

A soluble recombinant S100A8 protein with a high yield and purity was produced using Escherichia coli. Next, mice were immunized with recombinant S100A8 to obtain anti-human S100A8 monoclonal antibodies using hybridoma technology. Lastly, the high binding activity of the antibody was confirmed and its sequence was identified.

CONCLUSIONS

This method, including the production of antigens and antibodies, will be useful for the generation of hybridoma cell lines that produce anti-S100A8 monoclonal antibodies. Moreover, the sequence information of the antibody can be used to develop a recombinant antibody for use in various research and clinical applications.

Identifying Key Residues in Lysine Decarboxylase for Soluble Expression Using Consensus Design Soluble Mutant Screening (ConsenSing)

Although recent advances in deep learning approaches for protein engineering have enabled quick prediction of hot spot residues improving protein solubility, the predictions do not always correspond to an actual increase in solubility under experimental conditions. Therefore, developing methods that rapidly confirm the linkage between computational predictions and empirical results is essential to the success of improving protein solubility of target proteins. Here, we present a simple hybrid approach to computationally predict hot spots possibly improving protein solubility by sequence-based analysis and empirically explore valuable mutants using split GFP as a reporter system. Our approach, Consensus design Soluble Mutant Screening (ConsenSing), utilizes consensus sequence prediction to find hot spots for improvement of protein solubility and constructs a mutant library using Darwin assembly to cover all possible mutations in one pot but still keeps the library as compact as possible. This approach allowed us to identify multiple mutants of Escherichia coli lysine decarboxylase, LdcC, with substantial increases in soluble expression. Further investigation led us to pinpoint a single critical residue for the soluble expression of LdcC and unveiled its mechanism for such improvement. Our approach demonstrated that following a protein's natural evolutionary path provides insights to improve protein solubility and/or increase protein expression by a single residue mutation, which can significantly change the profile of protein solubility.

Recent trends in the modification of polyphenolic compounds using hydroxylation and glycosylation

Polyphenols are bioactive molecules that are used in therapeutics. Polyphenol hydroxylation and glycosylation have been shown to increase their bioavailability, solubility, bioactivity, and stability for use in various applications. Ortho-hydroxylation of polyphenols using tyrosinase allows high selectivity and yield without requiring a cofactor, while meta- and para-hydroxylation of polyphenols are mediated by site-specific hydroxylases and cytochrome P450s, although these processes are somewhat rare. O-glycosylation of polyphenols proceeds further after hydroxylation. The O-glycosylation reaction typically requires nucleotide diphosphate (NDP) sugar. However, amylosucrase (AS) has emerged as a promising enzyme for polyphenol glycosylation in large-scale production without requiring NDP-sugar. Overall, this review describes recent findings on the enzymatic mechanisms, enzyme engineering, and applications of enzymatic reactions.

CRISPR/deadCas9-based high-throughput gene doping analysis (HiGDA): A proof of concept for exogenous human erythropoietin gene doping detection

A genetic approach targeted toward improving athletic performance is called gene doping and is prohibited by the World Anti-Doping Agency. Currently, the clustered regularly interspaced short palindromic repeats-associated protein (Cas)-related assays have been utilized to detect genetic deficiencies or mutations. Among the Cas proteins, deadCas9 (dCas9), a nuclease-deficient mutant of Cas9, acts as a DNA binding protein with a target-specific single guide RNA. On the basis of the principles, we developed a dCas9-based high-throughput gene doping analysis for exogenous gene detection. The assay comprises two distinctive dCas9s, a magnetic bead immobilized capture dCas9 for exogenous gene isolation and a biotinylated dCas9 with streptavidin-polyHRP that enables rapid signal amplification. For efficient biotin labeling via maleimide-thiol chemistry, two cysteine residues of dCas9 were structurally validated, and the Cys574 residue was identified as an essential labeling site. As a result, we succeeded in detecting the target gene in a concentration as low as 12.3 fM (7.41 × 10⁵ copies) and up to 10 nM (6.07 × 10¹¹ copies) in a whole blood sample within 1 h with HiGDA. Assuming an exogenous gene transfer scenario, we added a direct blood amplification step to establish a rapid analytical procedure while detecting target genes with high sensitivity. Finally, we detected the exogenous human erythropoietin gene at concentrations as low as 2.5 copies within 90 min in 5 μL of the blood sample. Herein, we propose that HiGDA is a very fast, highly sensitive, and practical detection method for actual doping field in the future.

Orobol, 3'-hydroxy-genistein, suppresses the development and regrowth of cutaneous SCC

Chronic solar ultraviolet exposure is a major risk factor for cutaneous squamous cell carcinoma (cSCC), which is the second most common type of skin cancer. Our previous data showed that total protein and phosphorylation levels of T-LAK cell-originated protein kinase (TOPK) were enhanced in solar-simulated light (SSL)-induced skin carcinogenesis and overexpressed in actinic keratosis (AK) and cSCC human skin tissues compared to those in matched normal skin. Thus, targeting TOPK activity could be a helpful approach for treating cSCC. Our data showed that orobol directly binds to TOPK in an ATP-independent manner and inhibits TOPK kinase activity. Furthermore, orobol inhibited anchorage-independent colony formation by SCC12 cells in a dose-dependent manner. After discontinuing the treatment, patients commonly return to tumor-bearing conditions; therefore, therapy or intermittent dosing of drugs must be continued indefinitely. Thus, to examine the efficacy of orobol against the development and regrowth of cSCC, we established mouse models including prevention, and therapeutic models on the chronic SSL-irradiated SKH-1 hairless mice. Early treatment with orobol attenuates chronic SSL-induced cSCC development. Furthermore, orobol showed therapeutic efficacy after the formation of chronic SSL irradiation-induced tumor. In the mouse model with intermittent dosing of orobol, our data showed that re-application of orobol is effective for reducing tumor regrowth after discontinuation of treatment. Moreover, oncogenic protein levels were significantly attenuated by orobol treatment in the SSL-stimulated human skin. Thus, we suggest that orobol, as a promising TOPK inhibitor, could have an effective clinical approach to prevent and treat the development and regrowth of cSCC.

Biosynthesis of aliphatic plastic monomers with amino residues in Yarrowia lipolytica

Introduciton: The α,ω-diamines (NH₂-(CH₂)_n-NH₂) and ω -amino fatty acids (NH₂-(CH₂)_n-COOH) have been widely used as building blocks in polymerindustries. Medium- to long-chain (C₈ to C₁₈) fatty acid monomers with amino residues are almost exclusively produced via chemical processes that generate hazardous waste and induce severe environmental problems, such as global warming and pollution. Here, we present the construction platformstrains of Yarrowia lipolytica a cheese-ripening yeast, for direct biotransformation of hydrocarbons into medium- to long-chain α,ω-diamines and ωamino fatty acids using metabolic engineering of endogenous fatty acid ω- and β-oxidation pathways and introducing heterologous ω-transaminase in Y. lipolytica. Methods: We deleted six genes encoding the acyl-CoA oxidase (ACO1-6) and four fatty aldehyde dehydrogenase genes (FALDH1-4), which catalyze fatty acid β-oxidation and downstream oxidation of fatty aldehydes in Y. lipolytica, respectively. The ω-transaminase from Chromobacterium violaceum DSM30191 was introduced into the genome of the ΔPOX ΔFALDH strain under the control of Y. lipolytica-derived EXP1 promoters. Results and Discussion: The ΔPOX ΔFALDH strains with ω-CvTA successfully accumulated the corresponding C12 αω-diamines into a shaking culture medium with dodecane or dodecanol. In addition, these strains accumulated C₁₂ ω-amino fatty acids from dodecanoic acid. With the commercially available α,ω-diacid bioprocess, this yeast biosynthesis producing medium- and longchain α,ω-diamines and ω-amino fatty acids could complete the yeast platform technology generating all medium- and long-chain aliphatic polyamide monomers, α,ω-biofunctionalized with one or both carboxylic acid and amino residues.

Simple visualization method for the c.577del of erythropoietin variant: CRISPR/dCas9-based single nucleotide polymorphism diagnosis

One of the single nucleotide polymorphisms (SNPs) in human erythropoietin (hEPO), the c.577del variant, can produces 26 amino acids longer than the wild-type hEPO, posing a risk of misinterpretation in routine doping analysis. To prevent this, the World Anti-Doping Agency (WADA) included a procedure for reporting the sequencing results regarding the presence or absence of SNPs for suspected cases in the new version of the technical document for recombinant EPO in 2022. However, it is very expensive for anti-doping laboratories to purchase a gene sequencing analyzer, which costs hundreds of thousands of dollars, and only a few companies provide specific gene sequencing services with accredited certification. Therefore, in this study, we developed a simple visualization method for the c.577del of the EPO variant at the gene level. The gene fragment of the EPO gene, including c.577del, was amplified using a fast polymerase chain reaction (PCR), and the PCR products were incubated with the clustered regularly interspaced short palindromic repeats (CRISPR)/deadCas9 system using variant-specific single-guide RNA (sgRNA). This ribonucleoprotein complex binds specifically to the EPO variant gene fragment, causing a band shift on native-PAGE. We designed 4 sgRNAs that can bind only to the EPO variant or wild-type gene. In addition, an electrophoretic mobility shift assay on a gel demonstrated that one of the sgRNAs had a high level of specificity. Consequently, the c.577del variant was selectively detected by visualizing the target fragment of the gene on the gel within 3 h using only 3 μl of the whole blood.

Dual action of a tyrosinase-mesoporous silica nanoparticle complex for synergistic tissue adhesion

Bridging biological tissues for immediate adhesion and long-term sustainability was accomplished using a combination of mesoporous silica nanoparticles (MSNs) and tyrosinase. Tyrosinase-loaded MSNs provided rapid physical adsorption, while tyrosinase within MSNs induced enzymatic chemical bond gluing of tissues. This synergistic strategy has robust potential in tissue adhesives for clinical settings.

Flow cytometry-based rapid detection of Staphylococcus aureus and Pseudomonas aeruginosa using fluorescent antibodies

Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) are major pathogens frequently detected in food and beverage poisoning, and persistent infections. Therefore, the development of a rapid method that can detect these pathogens before serious multiplication is required. In this study, we established a flow cytometry (FCM)-based detection method that allows rapid acquisition of cell populations in fluid samples by using a fluorescent antibody against S. aureus or P. aeruginosa. Using this method, we detected these pathogens with a 10³ to 10⁵ CFU order of limit of detection value within 1 hour. The FCM-based method for the detection of S. aureus and P. aeruginosa offers the possibility of high-throughput analysis of pathogens in food, environmental, and clinical sources.

Stent expansion evaluated by optical coherence tomography and subsequent outcomes

Background

Regarding stent expansion indexes, previous optical coherence tomography (OCT) studies have shown minimal stent area (MSA) to be most predictive of adverse events.

Purpose

We sought to evaluate the impact of various stent expansion indexes by post-stent OCT on long-term clinical outcomes, and hence to find OCT-defined optimal stent expansion criteria.

Methods

Of the patients registered in the Yonsei OCT registry, a total of 1071 patients with 1123 native coronary artery lesions treated with new-generation drug-eluting stents under the OCT guidance and analyzable final post-stent OCT were included. Stent expansion indexes and different suboptimal stent expansion criteria were evaluated for their association with device-oriented clinical endpoints (DoCE) including cardiac death, target vessel-related myocardial infarction (TVMI) or stent thrombosis, and target lesion revascularization. Major safety events (MSE) included cardiac death, TVMI or stent thrombosis.

Results

The median follow-up period was 40.6 (interquartile range 22.0–50.0) months. As a continuous variable, MSA, adaptive volumetric stent expansion (stent volume/adaptive reference lumen volume) and overall volumetric stent expansion (stent volume/post-stent lumen volume) were significantly predictive of DoCE. As a categorical criteria, MSA <5.0 mm2 (hazard ratio [HR] 3.80; 95% confidence interval [CI] 1.53–9.45), MSA/distal reference lumen area <90% (HR 2.13; 95% CI 1.10–4.14), and overall volumetric stent expansion ≥96.6% (HR 2.38; 95% CI 1.09–5.22) were independently associated with DoCE after adjusting for confounders, and a total malapposition volume ≥7.0 mm3 (HR 3.38; 95% CI 1.05–10.93) was linked to MSE.

Conclusions

This OCT study highlights that sufficient stent expansion to achieve adequate absolute MSA and relative MSA by distal reference lumen area and alleviate significant malapposition is important to improve clinical outcome, but overall stent overexpansion may have deleterious effect.

Funding Acknowledgement

Type of funding sources: None.

Effect of early hysterectomy on a risk of incident cardiovascular disease in women: a nationwide population-based cohort study

Aim

Women who inevitably underwent surgical hysterectomy before natural menopause may have an earlier increase in hematocrit and storage iron than women who continue menstruation, thereby increasing the risk of cardiovascular disease (CVD) early. We aimed to evaluate the association of women with hysterectomy vs. without hysterectomy before their 50s with the risk of incident CVD.

Methods

This was a retrospective-cohort study, 135,575 women aged 40 to 50 years in 2011–2014 were extracted from the Korean Health Insurance Review and Assessment Service data and after propensity score matching, 55,539 pairs were included in hysterectomy and non-hysterectomy group respectively. The primary endpoint was major adverse cardiac and cerebrovascular events (MACCE), a composite of cardiovascular death, myocardial infarction (MI), stroke, and coronary artery revascularization.

Results

After adjustment for confounding factors, hysterectomy group had an increased risk of MACCE compared with non-hysterectomy group (hazard ratio [HR], 1.25; 95% confidence interval [CI], 1.09–1.44). Regarding individual outcomes, cardiovascular death, MI, and coronary revascularization were comparable between the groups, whereas, the risk of stroke was significantly higher in hysterectomy group than non-hysterectomy group (HR, 1.31; 95% CI, 1.12–1.53). Even after excluding women who underwent oophorectomy, hysterectomy group had a higher risk of MACCE than non-hysterectomy group (HR, 1.24; 95% CI 1.06–1.44).

Conclusions

Early surgical menopause due to hysterectomy, not hormonal menopause, was associated with an increased risk for a composite of CVD, especially stroke. This suggest that the role of “uterus” as well as sex hormones may be important for the sharp increase in the risk of CVD in women after menopause.

Funding Acknowledgement

Type of funding sources: None.

Optimal strategy for antiplatelet therapy after endovascular revascularization in patients with lower extremity artery disease

Background

The duration of antiplatelet therapy after endovascular revascularization in patients with lower extremity artery disease (LEAD) has not been well established. This study aimed to evaluate the clinical outcome according to the duration of dual antiplatelet therapy (DAPT) in real practice.

Methods

From April 2009 to June 2019, 376 patients with LEAD underwent successful endovascular revascularization. After the procedure, the received single antiplatelet therapy (SAPT) or DAPT of various durations were classified into two groups (SAPT or DAPT <6 months vs. DAPT ≥6 months). The primary outcomes were major adverse cardiovascular events (MACEs) and major adverse limb events (MALEs). The safety outcome was moderate-to-severe bleeding according to the Global Use of Strategies to Open Occluded Arteries (GUSTO) criteria.

Results

Over the 40-month follow-up period, MACE occurred less frequently in the DAPT ≥6 months group than that in the SAPT or DAPT <6 months group (12.4% vs. 23.8%; hazard ratio [HR]: 0.56; 95% confidence interval [CI]: 0.35–0.89; p=0.014) after inverse probability-weighted adjustment and propensity-score matching analysis (HR: 0.55, 95% CI; 0.30–0.99, p=0.048). The incidence of MALE did not show significant difference between the two groups (DAPT ≥6 months group: 17.1% vs. SAPT or DAPT <6 months group: 13.1%; HR: 1.05; 95% CI: 0.62–1.78; p=0.846). A significant difference between the DAPT ≥6 months group and the SAPT or DAPT <6 months group was not observed regarding the incidence of moderate-to-severe GUSTO bleeding.

Conclusions

In patients with LEAD, DAPT for ≥6 months after endovascular revascularization was associated with a lower incidence of MACE.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): National Research Foundation of Korea (NRF) grant funded by the government of Korea (MSIT) (No. 2019R1G1A1100442).

Generation of a recombinant antibody for sensitive detection of Pseudomonas aeruginosa

Pseudomonas aeruginosa (P. aeruginosa) is a major pathogen that causes nosocomial infections and often exhibits antibiotic resistance. Therefore, the development of an accurate method for detecting P. aeruginosa is required to control P. aeruginosa-related outbreaks. In this study, we established an enzyme-linked immunosorbent assay method for the sensitive detection of three P. aeruginosa strains, UCBPP PA14, ATCC 27853, and multidrug-resistant ATCC BAA-2108. We produced a recombinant antibody (rAb) against P. aeruginosa V‐antigen (PcrV), which is a needle tip protein of the type III secretion system of P. aeruginosa using mammalian cells with high yield and purity, and confirmed its P. aeruginosa binding efficiency. The rAb was paired with commercial anti-P. aeruginosa Ab for a sandwich ELISA, resulting in an antigen-concentration-dependent response with a limit of detection value of 230 CFU/mL. These results suggest that the rAb produced herein can be used for the sensitive detection of P. aeruginosa with a wide range of applications in clinical diagnosis and point-of-care testing.

Constructing multi-enzymatic cascade reactions for selective production of 6-bromoindirubin from tryptophan in Escherichia coli

6-Bromoindirubin (6BrIR), found in Murex sea snails, is a precursor of indirubin-derivatives anticancer drugs. However, its synthesis remains limited due to uncharacterized biosynthetic pathways and difficulties in site-specific bromination and oxidation at indole ring. Here, we present an efficient 6BrIR production strategy in E. coli by using four enzymes, i.e., tryptophan 6-halogenase fused with flavin reductase Fre (Fre-L3-SttH), tryptophanase (TnaA), toluene 4-monooxygenase (PmT4MO) and flavin-containing monooxygenase (MaFMO). Although most indole oxygenases preferentially oxygenate the electronically active C3 position of indole, PmT4MO was newly characterized to perform C2 oxygenation of 6-bromoindole with 45 % yield to produce 6-bromo-2-oxindole. In addition, 6BrIR was selectively generated without indigo and indirubin byproducts by controlling the reducing power of cysteine and oxygen supply during the MaFMO reaction. These approaches led to 34.1 mg/L 6BrIR productions, making it possible to produce the critical precursor of the anticancer drugs only from natural ingredients such as tryptophan, NaBr and oxygen. This article is protected by copyright. All rights reserved.

Thermostability engineering of an inulin fructotransferase for the biosynthesis of difructose anhydride I

The thermostability of enzymes is an essential factor that performs a vital role during practical applications. Inulin fructotransferases can efficiently convert inulin into bio-functional difructose anhydrides (DFAs). The present study aimed to improve the thermostability of a previously reported inulin fructotransferase, SpIFTase, and apply it to the biosynthesis of DFA I. In silico rational design was used to predict mutation sites, based on sequential and structural information. Two triple-site mutants, Q69L/Q234L/K310G and E201I/Q234L/K310G, were characterized and exhibited enhanced thermostability with approximately 5 °C higher in melting temperature (T_m), respectively, and a 45-fold longer half-life (t_1/2) at 70 °C, compared to that of SpIFTase. Molecular dynamic simulations and elaborate structural analysis suggested that the combinations of hydrophobic interaction, electrostatic potential distribution, and decreased flexibility via stabilization of loops and α-helix improved the thermostability of SpIFTase. Additionally, the promising mutants exhibited great potential to the industrial production of DFA I.

Synthesis of soluble melanin nanoparticles under acidic conditions using Burkholderia cepacia tyrosinase and their characterization

Melanin nanoparticles (MNPs) used for biomedical applications are often synthesized via the chemical auto-oxidation of catecholic monomers such as dopamine and 3,4-dihydroxyphenylalanine (DOPA) under alkaline conditions. However, the synthetic method for the chemical synthesis of MNP (cMNP) is relatively straightforward and more robust to control their homogenous particle size and morphology than the corresponding enzymatic synthetic methods. In this study, we demonstrated that the simple enzymatic synthesis of MNPs (eMNPs) with homogenous and soluble (<20 nm diameter) properties is possible using dopamine and Burkholderia cepacia tyrosinase (BcTy) under acidic conditions (i.e., pH 3.0). BcTy was highly reactive under pH 5.0, where the natural and chemical oxidation of catechol is complex, and thus melanin was synthesized via the hydroxylation of phenolic substrates. The detailed chemical analysis and characterization of the physical properties of the eMNPs confirmed the higher preservation of the catechol and primary amine moieties in the monomer substrate such as dopamine under acidic conditions. The eMNPs showed enhanced antioxidant activity and conferred stickiness to the formed hydrogel compared to the chemical auto-oxidation method owing to the large number of hydroxyl groups remaining such as catechol and quinone moieties. Because of these advantages and characteristics, the synthesis of MNPs using BcTy under acidic conditions can open a new path for their biomedical applications.

Melanin nanoparticles (MNPs) used for biomedical applications are often synthesized via the chemical auto-oxidation of catecholic monomers such as dopamine and 3,4-dihydroxyphenylalanine (DOPA) under alkaline conditions.

Comprehensive utilization of sucrose resources via chemical and biotechnological processes: A review

Sucrose, one of the most widespread disaccharides in nature, has been available in daily human life for many centuries. As an abundant and cheap sweetener, sucrose plays an essential role in our diet and the food industry. However, it has been determined that many diseases, such as obesity, diabetes, hyperlipidemia, etc., directly relate to the overconsumption of sucrose. It arouses many explorations for the conversion of sucrose to high-value chemicals. Production of valuable substances from sucrose by chemical methods has been studied since a half-century ago. Compared to chemical processes, biotechnological conversion approaches of sucrose are more environmentally friendly. Many enzymes can use sucrose as the substrate to generate functional sugars, especially those from GH68, GH70, GH13, and GH32 families. In this review, enzymatic catalysis and whole-cell fermentation of sucrose for the production of valuable chemicals were reviewed. The multienzyme cascade catalysis and metabolic engineering strategies were addressed.

Trap column-based intact mass spectrometry for rapid and accurate evaluation of protein molecular weight

The determination of the molecular weight (MW) of a protein using high-resolution mass spectrometry (MS) is a crucial tool used to confirm whether the protein was correctly expressed and adequately purified. However, a non-volatile buffer is normally used for protein purification and storage. Therefore, a pre-treatment step using ultrafiltration (UF) is required to exchange the buffer with a volatile buffer prior to the introduction of the protein sample into the MS equipment. This pre-treatment step is time-consuming. In this study, a trap column-based pre-treatment method applied in a nano-LC system was developed for rapid and convenient analysis of the MW of proteins. First, the trap column system was compared with the conventional UF treatment system and non-treatment system using bovine serum albumin. Subsequently, the trap column system was applied to analyze the MW of commercially available and lab-synthesized recombinant proteins. The intensity of the base peak and signal-to-noise ratio of the trap column-based pre-treated protein were higher than those of the UF-treated protein. Moreover, the entire automated procedure of the trap column-based system was conducted within 20 min, which confirms its use in versatile and accurate protein identification.

Trap column-based intact mass spectrometry for estimating the molecular weight of proteins.

Response After Repeated Ketamine Injections in a Rat Model of Neuropathic Pain

Ketamine, an N-methyl-D-aspartate antagonist, reduces pain by decreasing central sensitization and pain windup. However, chronic ketamine use can cause tolerance, dependency, impaired consciousness, urinary symptoms, and abdominal pain. This study aimed to investigate the effects of repeated ketamine injections and ketamine readministration after discontinuation in a rat model of neuropathic pain. To induce neuropathic pain, partial sciatic nerve ligation (PSNL) was performed in 15 male Wistar rats, and these animals were divided into three groups: PSNL (control), PSNL + ketamine 5 mg/kg (K5), and PSNL + ketamine 10 mg/kg (K10; n=5 each). Ketamine was injected intraperitoneally daily for 4 weeks, discontinued for 2 weeks, and then readministered for 1 week. Following PSNL, the mechanical withdrawal threshold was determined weekly using the Von Frey. The K10 group showed a significant increase in the mechanical withdrawal threshold, presented here as the target force (in g), at 21 and 28 days compared to the time point before ketamine injection (mean±SE, 276.0±24.0 vs. 21.6±2.7 and 300.0±0.0 vs. 21.6±2.7, respectively; P<0.01) and at 14, 21, and 28 days compared to the control group (108.2±51.2 vs. 2.7±1.3, 276.0±24.0 vs. 2.5±1.5, and 300.0±0.0 vs. 4.0±0.0, respectively; P<0.05). However, in the K10 group, the ketamine effects decreased significantly at 7 days after readministration compared to those after 28 days of repeated injections (P<0.05). In the K10 group, repeated ketamine injections showed a significant increase in antinociceptive effect for >2 weeks, but this ketamine effect decreased after drug readministration.

Regioselective One-Pot Synthesis of Hydroxy-(S)-Equols Using Isoflavonoid Reductases and Monooxygenases and Evaluation of the Hydroxyequol Derivatives as Selective Estrogen Receptor Modulators and Antioxidants

Several regiospecific enantiomers of hydroxy-(S)-equol (HE) were enzymatically synthesized from daidzein and genistein using consecutive reduction (four daidzein-to-equol–converting reductases) and oxidation (4-hydroxyphenylacetate 3-monooxygenase, HpaBC). Despite the natural occurrence of several HEs, most of them had not been studied owing to the lack of their preparation methods. Herein, the one-pot synthesis pathway of 6-hydroxyequol (6HE) was developed using HpaBC (EcHpaB) from Escherichia coli and (S)-equol-producing E. coli, previously developed by our group. Based on docking analysis of the substrate or products, a potential active site and several key residues for substrate binding were predicted to interpret the (S)-equol hydroxylation regioselectivity of EcHpaB. Through investigating mutations on the key residues, the T292A variant was verified to display specific mono-ortho-hydroxylation activity at C6 without further 3′-hydroxylation. In the consecutive oxidoreductive bioconversion using T292A, 0.95 mM 6HE could be synthesized from 1 mM daidzein, while 5HE and 3′HE were also prepared from genistein and 3′-hydroxydaidzein (3′HD or 3′-ODI), respectively. In the following efficacy tests, 3′HE and 6HE showed about 30∼200-fold higher EC50 than (S)-equol in both ERα and ERβ, and they did not have significant SERM efficacy except 6HE showing 10% lower β/α ratio response than that of 17β-estradiol. In DPPH radical scavenging assay, 3′HE showed the highest antioxidative activity among the examined isoflavone derivatives: more than 40% higher than the well-known 3′HD. In conclusion, we demonstrated that HEs could be produced efficiently and regioselectively through the one-pot bioconversion platform and evaluated estrogenic and antioxidative activities of each HE regio-isomer for the first time.

Generation of Recombinant Antibodies in HEK293F Cells for the Detection of Staphylococcus aureus

Staphylococcus aureus is a major resistant pathogen in clinical practice. Due to the increasing number of infections, rapid and sensitive detection of antibiotic-resistant S. aureus as well as antibiotic-sensitive S. aureus is important for the prevention and control of infectious diseases. In this study, we produced recombinant antibodies against S. aureus from mammalian human embryonic kidney 293 Freestyle cells with high yield and purity. These recombinant antibodies showed high binding affinity and low detection limit in both indirect and sandwich enzyme-linked immunosorbent assays for the detection of methicillin-resistant S. aureus and methicillin-sensitive S. aureus. These results suggest that the recombinant antibodies produced herein can be used for the accurate detection of S. aureus with a wild range of applications in medical diagnosis, food safety, and drug discovery.

An Integrative Multiomics Approach to Characterize Prebiotic Inulin Effects on Faecalibacterium prausnitzii

Faecalibacterium prausnitzii, a major commensal bacterium in the human gut, is well known for its anti-inflammatory effects, which improve host intestinal health. Although several studies have reported that inulin, a well-known prebiotic, increases the abundance of F. prausnitzii in the intestine, the mechanism underlying this effect remains unclear. In this study, we applied liquid chromatography tandem mass spectrometry (LC-MS/MS)-based multiomics approaches to identify biological and enzymatic mechanisms of F. prausnitzii involved in the selective digestion of inulin. First, to determine the preference for dietary carbohydrates, we compared the growth of F. prausnitzii in several carbon sources and observed selective growth in inulin. In addition, an LC-MS/MS-based intracellular proteomic and metabolic profiling was performed to determine the quantitative changes in specific proteins and metabolites of F. prausnitzii when grown on inulin. Interestingly, proteomic analysis revealed that the putative proteins involved in inulin-type fructan utilization by F. prausnitzii, particularly β-fructosidase and amylosucrase were upregulated in the presence of inulin. To investigate the function of these proteins, we overexpressed bfrA and ams, genes encoding β-fructosidase and amylosucrase, respectively, in Escherichia coli, and observed their ability to degrade fructan. In addition, the enzyme activity assay demonstrated that intracellular fructan hydrolases degrade the inulin-type fructans taken up by fructan ATP-binding cassette transporters. Furthermore, we showed that the fructose uptake activity of F. prausnitzii was enhanced by the fructose phosphotransferase system transporter when inulin was used as a carbon source. Intracellular metabolomic analysis indicated that F. prausnitzii could use fructose, the product of inulin-type fructan degradation, as an energy source for inulin utilization. Taken together, this study provided molecular insights regarding the metabolism of F. prauznitzii for inulin, which stimulates the growth and activity of the beneficial bacterium in the intestine.

Enhancing biosynthesis of 2'-Fucosyllactose in Escherichia coli through engineering lactose operon for lactose transport and α -1,2-Fucosyltransferase for solubility

2'-Fucosyllactose (2'-FL) is the most abundant oligosaccharide in human milk and one of the most actively studied human milk oligosaccharides (HMO). When 2'-FL is produced through biological production using a microorganism, like Escherichia coli, D-lactose is often externally fed as an acceptor substrate for fucosyltransferase (FT). When D-glucose is used as a carbon source for the cell growth and D-lactose is transported by lactose permease (LacY) in lac operon, D-lactose transport is under the control of catabolite repression (CR), limiting the supply of D-lactose for FT reaction in the cell, hence decreasing the production of 2'-FL. In this study, a remarkable increase of 2'-FL production was achieved by relieving the CR from the lac operon of the host E. coli BL21 and introducing adequate site-specific mutations into α-1,2-FT (FutC) for enhancement of catalytic activity and solubility. For the host engineering, the native lac promoter (P_lac ) was substituted for tac promoter (P_tac ), so that the lac operon could be turned on, but not subjected to CR by high D-glucose concentration. Next, for protein engineering of FutC, family multiple sequence analysis for conserved amino acid sequences and protein-ligand substrate docking analysis led us to find several mutation sites, which could increase the solubility of FutC and its activity. As a result, a combination of four mutation sites (F40S/Q150H/C151R/Q239S) was identified as the best candidate, and the quadruple mutant of FutC enhanced 2'-FL titer by 2.4-fold. When the above-mentioned E. coli mutant host transformed with the quadruple mutant of futC was subjected to fed-batch culture, 40 g l^-1 of 2'-FL titer was achieved with the productivity of 0.55 g l^-1 h^-1 and the specific 2'-FL yield of 1.0 g g^-1 DCW. This article is protected by copyright. All rights reserved.

Rationally Designed Eugenol-Based Chain Extender for Self-Healing Polyurethane Elastomers

Bio-based polyurethane (PU) has recently drawn our attention due to the increasing interest in sustainability and the risks involved with petroleum depletion. Herein, bio-based self-healing PU with a novel polyol, i.e., eugenol glycol dimer (EGD), was synthesized and characterized for the first time. EGD was designed to have pairs of primary, secondary, and aromatic alcohols, which all are able to be involved in urethane bond formation and to show self-healing and antioxidant effects. EGD was incorporated into a mixture of the prepolymer of polyol (tetramethylene ether glycol) and 4,4'-methylene diphenyl diisocyanate to synthesize PU. EGD-PU showed excellent self-healing properties (99.84%), and it maintained its high self-healing property (84.71%) even after three repeated tests. This dramatic self-healing was induced through transcarbamoylation by the pendant hydroxyl groups of EGD-PU. The excellent antioxidant effect of EGD-PU was confirmed by 2,2-diphenyl-1-picrylhydrazyl analysis. Eugenol-based EGD is a promising polyol chain extender that is required in the production of bio-based, self-healing, and recyclable polyurethane; therefore, EGD-PU can be applied to bio-based self-healable films or coating materials as a substitute for petroleum-based PU.

Polyphenol-Hydroxylating Tyrosinase Activity under Acidic pH Enables Efficient Synthesis of Plant Catechols and Gallols

Tyrosinase is generally known as a melanin-forming enzyme, facilitating monooxygenation of phenols, oxidation of catechols into quinones, and finally generating biological melanin. As a homologous form of tyrosinase in plants, plant polyphenol oxidases perform the same oxidation reactions specifically toward plant polyphenols. Recent studies reported synthetic strategies for large scale preparation of hydroxylated plant polyphenols, using bacterial tyrosinases rather than plant polyphenol oxidase or other monooxygenases, by leveraging its robust monophenolase activity and broad substrate specificity. Herein, we report a novel synthesis of functional plant polyphenols, especially quercetin and myricetin from kaempferol, using screened bacterial tyrosinases. The critical bottleneck of the biocatalysis was identified as instability of the catechol and gallol under neutral and basic conditions. To overcome such instability of the products, the tyrosinase reaction proceeded under acidic conditions. Under mild acidic conditions supplemented with reducing agents, a bacterial tyrosinase from Bacillus megaterium (BmTy) displayed efficient consecutive two-step monophenolase activities producing quercetin and myricetin from kaempferol. Furthermore, the broad substrate specificity of BmTy toward diverse polyphenols enabled us to achieve the first biosynthesis of tricetin and 3'-hydroxyeriodictyol from apigenin and naringenin, respectively. These results suggest that microbial tyrosinase is a useful biocatalyst to prepare plant polyphenolic catechols and gallols with high productivity, which were hardly achieved by using other monooxygenases such as cytochrome P450s.

Expression of soluble recombinant human matrix metalloproteinase 9 and generation of its monoclonal antibody

We have successfully produced a recombinant human matrix metalloproteinase 9 (hMMP9) antigen with high yield and purity and used it to generate a hybridoma cell-culture-based monoclonal anti-hMMP9 antibody. We selected the most effective antibody for binding antigens and successfully identified its nucleotide sequence. The entire antigen and antibody developmental procedures described herein can be a practical approach for producing large amounts of monoclonal antibodies against hMMP9 and other antigens of interest. Additionally, the nucleotide sequence information of the anti-hMMP9 monoclonal antibody revealed herein will be useful for the generation of recombinant antibodies or antibody fragments against hMMP9.

Novel enzymatic cross-linking-based hydrogel nanofilm caging system on pancreatic β cell spheroid for long-term blood glucose regulation

Pancreatic β cell therapy for type 1 diabetes is limited by low cell survival rate owing to physical stress and aggressive host immune response. In this study, we demonstrate a multilayer hydrogel nanofilm caging strategy capable of protecting cells from high shear stress and reducing immune response by interfering cell-cell interaction. Hydrogel nanofilm is fabricated by monophenol-modified glycol chitosan and hyaluronic acid that cross-link each other to form a nanothin hydrogel film on the cell surface via tyrosinase-mediated reactions. Furthermore, hydrogel nanofilm formation was conducted on mouse β cell spheroids for the islet transplantation application. The cytoprotective effect against physical stress and the immune protective effect were evaluated. Last, caged mouse β cell spheroids were transplanted into the type 1 diabetes mouse model and successfully regulated its blood glucose level. Overall, our enzymatic cross-linking-based hydrogel nanofilm caging method will provide a new platform for clinical applications of cell-based therapies.

High-yield production of (R)-acetoin in Saccharomyces cerevisiae by deleting genes for NAD(P)H-dependent ketone reductases producing meso-2,3-butanediol and 2,3-dimethylglycerate

Acetoin is widely used in food and cosmetics industries as a taste and fragrance enhancer. To produce (R)-acetoin in Saccharomyces cerevisiae, acetoin biosynthetic genes encoding α-acetolactate synthase (AlsS) and α-acetolactate decarboxylase (AlsD) from Bacillus subtilis and water-forming NADH oxidase (NoxE) from Lactococcus lactis were integrated into delta-sequences in JHY605 strain, where the production of ethanol, glycerol, and (R,R)-2,3-butanediol (BDO) was largely eliminated. We further improved acetoin production by increasing acetoin tolerance by adaptive laboratory evolution, and eliminating other byproducts including meso-2,3-BDO and 2,3-dimethylglycerate, a newly identified byproduct. Ara1, Ypr1, and Ymr226c (named Ora1) were identified as (S)-alcohol-forming reductases, which can reduce (R)-acetoin to meso-2,3-BDO in vitro. However, only Ara1 and Ypr1 contributed to meso-2,3-BDO production in vivo. We elucidate that Ora1, having a substrate preference for (S)-acetoin, reduces (S)-α-acetolactate to 2,3-dimethylglycerate, thus competing with AlsD-mediated (R)-acetoin production. By deleting ARA1, YPR1, and ORA1, 101.3 g/L of (R)-acetoin was produced with a high yield (96% of the maximum theoretical yield) and high stereospecificity (98.2%).

New application of the CRISPR-Cas9 system for site-specific exogenous gene doping analysis

The increased potential for gene doping since the introduction of gene therapy presents the need to develop antidoping assays. We therefore aimed to develop a quick and simple method for the detection of specifically targeted exogenous doping genes utilizing an in vitro clustered regularly interspaced short palindromic repeats-CRISPR associated protein 9 (CRISPR-Cas9) system. A human erythropoietin (hEPO) is a drug frequently used for doping in athletes, and gene doping using gene transfer techniques may be attempted. Therefore, we selected hEPO gene as a model of exogenous doping gene, and complemental single guide RNA (sgRNA) was designed to specifically bind to the four exon-exon junctions in the hEPO cDNA. For the rapid reaction of CRISPR-Cas9, further optimization was performed using an open-source program (CRISPOR) that avoids TT and GCC motifs before the protospacer adjacent motif (PAM) domain and predicts the efficiency of the sgRNA. We optimized the in vitro Cas9 assay and dual use of sgRNA for double cleavage and identified the limit of detection (LOD) of the 1.25 nM of the double cleavage method. We expect that the improved CRISPR-Cas9 method can be used for antidoping analysis of gene doping.

Diagnostic ability of salivary matrix metalloproteinase-9 lateral flow test point-of-care test for periodontitis

AIM

This cross-sectional study aimed to examine the diagnostic ability of salivary matrix metalloproteinase (MMP)-9 lateral flow test (LFT) point-of-care (POC) kit and develop an algorithm for diagnosis of periodontitis.

MATERIALS AND METHODS

Through Seoul National Dental Hospital, 137 participants (46 LFT negatives, 91 LFT positives) were recruited. For salivary diagnostics, 150 μl of the unstimulated saliva was applied to LFT-POC kit. To make a diagnosis of periodontitis, stage II-IV in modified new international classification system was used. Covariates encompassing age, sex, smoking and obesity were evaluated through face-to-face interview. Enzyme-linked immunosorbent assay was used for quantification of salivary MMP-9. To develop a diagnostic algorithm, multivariable logistic regression analysis was used. Receiver operating characteristic curve was applied for evaluating diagnostic ability.

RESULTS

Diagnostic ability of salivary MMP-9 LFT-POC test was 0.82 (sensitivity of 0.92, specificity of 0.72) in total participants. Diagnostic algorithm using POC test resulted in a response equation, that is algorithm score = -3.675 + 2.877*LFT + 0.034*age + 0.121*sex + 0.372*smoking + 0.192*obesity. Diagnostic ability of the algorithm was 0.88 (sensitivity of 0.92, specificity of 0.85) with cut-off score of 0.589.

CONCLUSIONS

Salivary MMP-9 LFT-POC kit showed appropriate diagnostic ability for periodontitis and would be an efficient tool for screening of periodontitis.

Application of Random Mutagenesis and Synthetic FadR Promoter for de novo Production of ω-Hydroxy Fatty Acid in Yarrowia lipolytica

As a means to develop oleaginous biorefinery, Yarrowia lipolytica was utilized to produce ω-hydroxy palmitic acid from glucose using evolutionary metabolic engineering and synthetic FadR promoters for cytochrome P450 (CYP) expression. First, a base strain was constructed to produce free fatty acids (FFAs) from glucose using metabolic engineering strategies. Subsequently, through ethyl methanesulfonate (EMS)-induced random mutagenesis and fluorescence-activated cell sorting (FACS) screening, improved FFA overproducers were screened. Additionally, synthetic promoters containing bacterial FadR binding sequences for CYP expression were designed to respond to the surge of the concentration of FFAs to activate the ω-hydroxylating pathway, resulting in increased transcriptional activity by 14 times from the third day of culture compared to the first day. Then, endogenous alk5 was screened and expressed using the synthetic FadR promoter in the developed strain for the production of ω-hydroxy palmitic acid. By implementing the synthetic FadR promoter, cell growth and production phases could be efficiently decoupled. Finally, in batch fermentation, we demonstrated de novo production of 160 mg/L of ω-hydroxy palmitic acid using FmeN3-TR1-alk5 in nitrogen-limited media. This study presents an excellent example of the production of ω-hydroxy fatty acids using synthetic promoters with bacterial transcriptional regulator (i.e., FadR) binding sequences in oleaginous yeasts.

Development of an in vitro coculture device for the investigation of host-microbe interactions via integrative multiomics approaches

The commensal gut bacterium Akkermansia muciniphila is well known as a promising probiotic candidate that improves host health and prevents diseases. However, the biological interaction of A. muciniphila with human gut epithelial cells has rarely been explored for use in biotherapeutics. Here, we developed an in vitro device that simulates the gut epithelium to elucidate the biological effects of living A. muciniphila via multiomics analysis: the Mimetic Intestinal Host-Microbe Interaction Coculture System (MIMICS). We demonstrated that both human intestinal epithelial cells (Caco-2) and the anaerobic bacterium A. muciniphila can remain viable for 12 h after coculture in the MIMICS. The transcriptomic and proteomic changes (cell-cell junctions, immune responses, and mucin secretion) in gut epithelial cells treated with A. muciniphila closely correspond with those reported in previous in vivo studies. In addition, our proteomic and metabolomic results revealed that A. muciniphila activates glucose and lipid metabolism in gut epithelial cells, leading to an increase in ATP production. This study suggests that A. muciniphila improves metabolism for ATP production in gut epithelial cells and that the MIMICS may be an effective general tool for evaluating the effects of anaerobic bacteria on gut epithelial cells.

Development of cellulose-based conductive fabrics with electrical conductivity and flexibility

This study aimed to produce cellulose-based conductive fabrics with electrical conductivity and flexibility. Bacterial cellulose (BC) and three chemical cellulose (CC), namely methyl cellulose (MC), hydroxypropyl cellulose (HPMC) and carboxymethyl cellulose (CMC) were in situ polymerized with aniline and the four conductive cellulose fabrics were compared and evaluated. Matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy analysis confirmed that three CC-PANI composites displayed longer and more stable polymerization pattern than BC-PANI because of the different polymerization method: bulk polymerization for BC-PANI and emulsion polymerization for CC-PANI, respectively. The electrical conductivity of BC-PANI and CC-PANI were ranging from 0.962 × 10-2 S/cm to 2.840 × 10-2 S/cm. MC-PANI showed the highest electrical conductivity among the four conductive cellulose fabrics. The flexibility and crease recovery results showed that MC-PANI had the highest flexibility compared to BC-PANI, HPMC-PANI, and CMC-PANI. These results have confirmed that the electrical conductivity and flexibility were influenced by the type of cellulose, and MC-PANI was found to have the best performance in the electrical conductivity and flexibility.

Characterization of a Tryptophan 6-Halogenase from Streptomyces albus and Its Regioselectivity Determinants

Tryptophan halogenases are found in diverse organisms and catalyze regiospecific halogenation. They play an important role in the biosynthesis of halogenated indole alkaloids, which are biologically active and of therapeutic importance. Here, a tryptophan 6-halogenase (SatH) from Streptomyces albus was characterized by using a whole-cell reaction system in Escherichia coli. SatH showed substrate specificity for chloride and bromide ions, leading to regiospecific halogenation at the C6-position of l-tryptophan. In addition, SatH exhibited higher performance in bromination than that of previously reported tryptophan halogenases in the whole-cell reaction system. Through structure-based protein mutagenesis, it has been revealed that two consecutive residues, A78/V79 in SatH and G77/I78 in PyrH, are key determinants in the regioselectivity difference between tryptophan 6- and 5-halogenases. Substituting the AV with GI residues switched the regioselectivity of SatH by moving the orientation of tryptophan. These data contribute to an understanding of the key residues that determine the regioselectivity of tryptophan halogenases.

Fabrication of polyphenol-incorporated anti-inflammatory hydrogel via high-affinity enzymatic crosslinking for wet tissue adhesion

Epigallocatechin gallates (EGCGs), isolated from green tea, have intrinsic properties such as anti-oxidant, anti-inflammation, and radical scavenger effects. In this study, we report a tissue adhesive and anti-inflammatory hydrogel formed by high-affinity enzymatic crosslinking of polyphenolic EGCGs. A mixture of EGCG conjugated hyaluronic acids (HA_E) and tyramine conjugated hyaluronic acids (HA_T) was reacted with tyrosinase isolated from Streptomyces avermitillis (SA_Ty) to form that displayed fast enzyme kinetic to form a crosslinked adhesive hydrogel. A 1,2,3-trihydroxyphenyl group in EGCG displayed a high affinity to SA_Ty that allowed HA_E to be quickly oxidized and crosslinked with HA_T to form HA_T and HA_E mixed hydrogel (HA_TE). We then compared the HA_TE hydrogel with commercially available tissue adhesives, such as cyanoacrylate and fibrin glue. We report that the HA_TE exhibited the highest tissue adhesiveness both in wet and dry conditions. Furthermore, HA_TE successfully closed a skin wound and displayed insignificant host tissue responses. This demonstrates that polyphenol-incorporated anti-inflammatory hydrogel may provide a robust tissue adhesive platform for clinical applications.

Prospective randomized comparison of cerebrospinal fluid aspiration and conventional popping methods using 27-gauge spinal needles in patients undergoing spinal anaesthesia

Background

Performing spinal anaesthesia using the conventional popping method with a 27-gauge (27G) spinal needle is technically difficult. In this study, we compared the aspiration and conventional popping method for spinal anaesthesia using 27G Quincke-type needles.

Methods

This prospective, randomized study enrolled 90 patients, aged 19 to 65 years, with American Society of Anesthesiologists physical status I-III, who were undergoing spinal anaesthesia. Patients were randomly assigned to one of two groups using a computer-generated random number table: patients receiving spinal anaesthesia using the aspiration method, in which the needle is advanced with continuous aspiration, or the conventional popping method. The primary outcome measure was the success rate of the first attempt to perform dural puncture. Number of attempts and passages, withdrawal cases, successful attempt time, total procedure time, and actual depth of dural puncture were recorded.

Results

Eighty-eight patients were included in the study. In the aspiration group, the success rate of first attempt for dural puncture was 93.3%, compared with 72.1% in the popping group (P = 0.019). Success involving needle withdrawal was recorded in 4 (8.9%) patients in the aspiration group and 13 (30.2%) in the popping group (P = 0.024). In the popping group, the number of attempts was significantly higher (P = 0.044), and total procedure time was significantly longer (P = 0.023). Actual depths of dural puncture were deeper in the popping group than in the aspiration group (P = 0.019).

Conclusions

The aspiration method using a 27G Quincke-type needle offers clinical benefits for dural puncture compared with the conventional popping method for spinal anaesthesia.

Trial registration

Clinical research information service number: KCT0002815, registered 21/Apr/2018. Retrospectively registered.

Engineering Streptomyces coelicolor for production of monomethyl branched chain fatty acids

Branched chain fatty acids (BCFA) are an appealing biorefinery-driven target of fatty acid (FA) production. BCFAs typically have lower melting points compared to straight chain FAs, making them useful in lubricants and biofuels. Actinobacteria, especially Streptomyces species, have unique secondary metabolism that are capable of producing not only antibiotics, but also high percentage of BCFAs in their membrane lipids. Since biosynthesis of polyketide (PK) and FA partially share common pathways to generate acyl-CoA precursors, in theory, Streptomyces sp. with high levels of PK antibiotics production can be easily manipulated into strains producing high levels of BCFAs. To increase the percentage of the BCFA moieties in lipids, we redirected acyl-CoA precursor fluxes from PK into BCFAs using S. coelicolor M1146 (M1146) as a host strain. In addition, 3-ketoacyl acyl carrier protein synthase III and branched chain α-keto acid dehydrogenase were overexpressed to push fluxes of branched chain acyl-CoA precursors towards FA synthesis. The maximum titer of 354.1 mg/L BCFAs, 90.3% of the total FA moieties, was achieved using M1146_dD-B, fadD deletion and bkdABC overexpression mutant of M1146 strain. Cell specific yield of 64.4 mg/L/g_cell was also achieved. The production titer and specific yield are the highest ever reported in bacterial cells, which provides useful insights to develop an efficient host strain for BCFAs.

Production of 12-hydroxy dodecanoic acid methyl ester using a signal peptide sequence-optimized transporter AlkL and a novel monooxygenase

In this study, a signal peptide of AlkL was replaced with other signal peptides to improve the soluble expression and thereby facilitate the transport of dodecanoic acid methyl ester (DAME) substrate into the E. coli. Consequently, AlkL with signal peptide FadL (AlkL_f) showed higher transport activity toward DAME. Furthermore, the promoter optimization for the efficient heterologous expression of the transporter AlkL_f and alkane monooxygenase (AlkBGT) system was conducted and resulted in increased ω-oxygenation activity of AlkBGT system. Moreover, bioinformatic studies led to the identification of novel monooxygenase from Pseudomonas pelagia (Pel), which exhibited 20% higher activity towards DAME as substrate compared to AlkB. Finally, the construction of a chimeric transporter and the expression of newly identified monooxygenase enabled the production of 44.8 ± 7.5 mM of 12-hydroxy dodecanoic acid methyl ester (HADME) and 31.8 ± 1.7 mM of dodecanedioic acid monomethyl ester (DDAME) in a two-phase reaction system.

Prevalence of measles IgG antibodies among immigrant workers in South Korea

Background

After the national vaccination for measles was introduced in 1985, the measles has been controlled in South Korea despite the epidemic in 2000-2001. Current cases in Korea were assumed to be transmitted from outside the country. Because the dynamics and social changes of the population has emerged as important factors in the measles epidemic, this study aimed to assess the prevalence of measles IgG antibodies among immigrant workers.

Methods

The cross sectional seroprevalence survey was conducted in Gyeongsangnamdo province, Korea. Because the representative sampling frame could not be possible, the voluntary foreign workers who have agreed informed consents with a translated format into the native language, participated in this study. IgG antibodies of measles was examined by ELISA using the automation equipment (BEP III- ELISA). This study obtained the approval of Dong-A University Clinical Research Ethics Review Committee.

Results

364 people of foreign workers participated in the study. Regional distribution for study participants was composed of 30 people in Vietnam (16.5%), Uzbekistan 71 people (19.5%), Thailand 70 people (19.2%), China 60 people (16.5%), Philippines 36 people (9.9%), and Indonesia 32 people (8.8%). The average age was 33.0 ± 6.9 years old and 86.5% of the total was men. High school or higher education accounted for 74%. 93.7% showed positivity (95% CI: 95.7-98.9%) for measles IgG antibody and 3.6% showed equivocal.

Conclusions

The measles seropositivity among immigrant workers in Korea was considered to be at the recommended level.

Key messages

The measles seropositivity among immigrant workers in Korea was considered to be at the recommended level. International cooperation is needed to prevent global measles epidemic.

Biosynthesis of the human milk oligosaccharide 3-fucosyllactose in metabolically engineered Escherichia coli via the salvage pathway through increasing GTP synthesis and β-galactosidase modification

3-Fucosyllactose (3-FL) is one of the major fucosylated oligosaccharides in human milk. Along with 2'-fucosyllactose (2'-FL), it is known for its prebiotic, immunomodulator, neonatal brain development, and antimicrobial function. Whereas the biological production of 2'-FL has been widely studied and made significant progress over the years, the biological production of 3-FL has been hampered by the low activity and insoluble expression of α-1,3-fucosyltransferase (FutA), relatively low abundance in human milk oligosaccharides compared with 2'-FL, and lower digestibility of 3-FL than 2'-FL by bifidobacteria. In this study, we report the gram-scale production of 3-FL using E. coli BL21(DE3). We previously generated the FutA quadruple mutant (mFutA) with four site mutations at S46F, A128N, H129E, Y132I, and its specific activity was increased by nearly 15 times compared with that of wild-type FutA owing to the increase in k_cat and the decrease in K_m . We overexpressed mFutA in its maximum expression level, which was achieved by the optimization of yeast extract concentration in culture media. We also overexpressed L-fucokinase/GDP- L-fucose pyrophosphorylase to increase the supply of GDP-fucose in the cytoplasm. To increase the mass of recombinant whole-cell catalysts, the host E. coli BW25113 was switched to E. coli BL21(DE3) because of the lower acetate accumulation of E. coli BL21(DE3) than that of E. coli BW25113. Finally, the lactose operon was modified by partially deleting the sequence of LacZ (lacZΔm15) for better utilization of D-lactose. Production using the lacZΔm15 mutant yielded 3-FL concentration of 4.6 g/L with the productivity of 0.076 g·L^-1 ·hr^-1 and the specific 3-FL yield of 0.5 g/g dry cell weight.

Structural characterization of phosphoethanolamine-modified lipid A from probiotic Escherichia coli strain Nissle 1917

Gut microbiota, a complex microbial community inhabiting human or animal intestines recently regarded as an endocrine organ, has a significant impact on human health. Probiotics can modulate gut microbiota and the gut environment by releasing a range of bioactive compounds. Escherichia coli (E. coli) strain Nissle 1917 (EcN), a Gram-negative bacterial strain, has been used to treat gastrointestinal (GI) disorders (i.e., inflammatory bowel disease, diarrhea, ulcerative colitis, and so on). However, endotoxicity of lipopolysaccharide (LPS), a major component of the cell wall of Gram-negative bacteria in the gut, is known to have a strong influence on gut inflammation and maintenance of gut homeostasis. Therefore, characterizing the chemical structure of lipid A which determines the toxicity of LPS is needed to understand nonpathogenic colonization and commensalism properties of EcN in the gut more precisely. In the present study, MALDI multiple-stage mass spectrometry analysis of lipid A extracted from EcN demonstrates that hexaacylated lipid A (m/z 1919.19) contains a glucosamine disaccharide backbone, a myristate, a laurate, four 3-hydroxylmyristates, two phosphates, and phosphoethanolamine (PEA). PEA modification of lipid A is known to contribute to cationic antimicrobial peptide (CAMP) resistance of Gram-negative bacteria. To confirm the role of PEA in CAMP resistance of EcN, minimum inhibitory concentrations (MICs) of polymyxin B and colistin were determined using a wild-type strain and a mutant strain with deletion of eptA gene encoding PEA transferase. Our results confirmed that MICs of polymyxin B and colistin for the wild-type were twice as high as those for the mutant. These results indicate that EcN can more efficiently colonize the intestine through PEA-mediated tolerance despite the presence of CAMPs in human gut such as human defensins. Thus, EcN can be used to help treat and prevent many GI disorders.