Functional Group-Dependent Proton Conductivity of Phosphoric Acid-Doped Ion-Pair Coordinated Polymer Electrolytes: A Molecular Dynamics Study.

Toward deployment of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) in our daily lives, multiple research efforts have been dedicated to develop high-performance phosphate-doped polymer electrolytes. Recently, ion-pair coordinated polymers have garnered attention for their high stability and proton conductivity. However, a comprehensive understanding of how proton transport properties are modified by the functional groups present in these polymers is still lacking. In this study, we employ molecular dynamics (MD) simulations to investigate the impact of different functional group types and conversion ratios on conductivity. We find that Grotthuss-type hopping transport predominantly governs the overall conductivity, surpassing vehicular transport by factors of 100-1000. As conductivity scales with proton concentration, we observe that less-bulky functional groups offer advantages by minimizing the volume expansion associated with increased conversion ratios. Additionally, we show that a strong ion-pair interaction between the cationic functional group and the phosphate anion disrupts the suitable intermolecular orientations required for efficient proton hopping between phosphate and phosphoric acid molecules, thereby diminishing the proton conductivity. Our study underscores the importance of optimizing the strength of ion-pair interactions to balance stability and proton conductivity, thus paving the way for the development of ion-pair coordinated polymer electrolytes with improved performance.

Potential use of microbial engineering in single-cell protein production.

Single-cell proteins (SCPs) have been widely used in human food and animal feed applications, still, there are challenges in their production and commercialization. Recently, advances in microbial synthetic biology, genomic engineering, and biofoundry technologies have offered capabilities to effectively and rapidly engineer microorganisms for improving the productivity, nutritional, and functional quality of SCPs. In this review, we discuss various synthetic biology, genomic engineering, and biofoundry tools that can be harnessed for SCP production and genetic modification. We also describe the current and potential applications of genetic modification in producing intermediate feedstocks, as well as biomass-based and multifunctional SCPs. Finally, we discuss the technological and policy-control related challenges encountered when deploying genetic modification in SCP production for animal feed and human food applications.

Comparison of Diagnostic Performance in Mammography Assessment: Radiologist with Reference to Clinical Information Versus Standalone Artificial Intelligence Detection.

We compared diagnostic performances between radiologists with reference to clinical information and standalone artificial intelligence (AI) detection of breast cancer on digital mammography. This study included 392 women (average age: 57.3 ± 12.1 years, range: 30−94 years) diagnosed with malignancy between January 2010 and June 2021 who underwent digital mammography prior to biopsy. Two radiologists assessed mammographic findings based on clinical symptoms and prior mammography. All mammographies were analyzed via AI. Breast cancer detection performance was compared between radiologists and AI based on how the lesion location was concordant between each analysis method (radiologists or AI) and pathological results. Kappa coefficient was used to measure the concordance between radiologists or AI analysis and pathology results. Binominal logistic regression analysis was performed to identify factors influencing the concordance between radiologists' analysis and pathology results. Overall, the concordance was higher in radiologists' diagnosis than on AI analysis (kappa coefficient: 0.819 vs. 0.698). Impact of prior mammography (odds ratio (OR): 8.55, p < 0.001), clinical symptom (OR: 5.49, p < 0.001), and fatty breast density (OR: 5.18, p = 0.008) were important factors contributing to the concordance of lesion location between radiologists' diagnosis and pathology results.

Biosynthesis of Commodity Chemicals From Oil Palm Empty Fruit Bunch Lignin.

Lignin is one of the most abundant natural resources that can be exploited for the bioproduction of value-added commodity chemicals. Oil palm empty fruit bunches (OPEFBs), byproducts of palm oil production, are abundant lignocellulosic biomass but largely used for energy and regarded as waste. Pretreatment of OPEFB lignin can yield a mixture of aromatic compounds that can potentially serve as substrates to produce commercially important chemicals. However, separation of the mixture into desired individual substrates is required, which involves expensive steps that undermine the utility of OPEFB lignin. Here, we report successful engineering of microbial hosts that can directly utilize heterogeneous mixtures derived from OPEFB lignin to produce commodity chemicals, adipic acid and levulinic acid. Furthermore, the corresponding bioconversion pathway was placed under a genetic controller to autonomously activate the conversion process as the cells are fed with a depolymerized OPEFB lignin mixture. This study demonstrates a simple, one-pot biosynthesis approach that directly utilizes derivatives of agricultural waste to produce commodity chemicals.

Engineering Yarrowia lipolytica towards food waste bioremediation: Production of fatty acid ethyl esters from vegetable cooking oil.

Fatty acid ethyl esters (FAEEs) can potentially be used as biodiesel, which provides a renewable alternative to petroleum-derived diesel. FAEEs are primarily produced via transesterification of vegetable oil with an alcohol catalyzed by a strong base, which raises safety concerns. Microbial production presents a more environmentally sustainable method for FAEE production, and by harnessing the ability of oleaginous yeast Yarrowia lipolytica to degrade and assimilate hydrophobic substrates, FAEE production could be coupled to food waste bioremediation. In this study, we engineered Y. lipolytica to produce FAEEs from dextrose as well as from vegetable cooking oil as a model food waste. Firstly, we introduced pyruvate decarboxylase (pdc) and alcohol dehydrogenase II (adhB) from Zymomonas mobilis to reconstitute the heterologous pathway for ethanol production. Second, we introduced and compared two heterologous wax ester synthases ws2 and maqu_0168 from Marinobacter sp. for FAEE biosynthesis. Next, we disrupted competitive pathways to increase fatty acyl-CoA pool, and optimized carbon sources and cell density for shake-flask fermentation. The engineered strain showed a 24-fold improvement in FAEE production titer over the starting strain. Moreover, we explored the potential of the engineered strain for FAEE production from the model food waste by supplementing vegetable cooking oil to the culture medium. To the best of our knowledge, this is the first report on FAEE production with the supplementation of vegetable cooking oil in Y. lipolytica. These findings provide valuable insights into the engineering of Y. lipolytica for high-level production of FAEEs and its utilization in food waste bioremediation.

Synthetic biology toolkits and applications in Saccharomyces cerevisiae.

Synthetic biologists construct biological components and systems to look into biological phenomena and drive a myriad of practical applications that aim to tackle current global challenges in energy, healthcare and the environment. While most tools have been established in bacteria, particularly Escherichia coli, recent years have seen parallel developments in the model yeast strain Saccharomyces cerevisiae, one of the most well-understood eukaryotic biological system. Here, we outline the latest advances in yeast synthetic biology tools based on a framework of abstraction hierarchies of parts, circuits and genomes. In brief, the creation and characterization of biological parts are explored at the transcriptional, translational and post-translational levels. Using characterized parts as building block units, the designing of functional circuits is elaborated with examples. In addition, the status and potential applications of synthetic genomes as a genome level platform for biological system construction are also discussed. In addition to the development of a toolkit, we describe how those tools have been applied in the areas of drug production and screening, study of disease mechanisms, pollutant sensing and bioremediation. Finally, we provide a future outlook of yeast as a workhorse of eukaryotic genetics and a chosen chassis in this field.

Rewriting the Metabolic Blueprint: Advances in Pathway Diversification in Microorganisms.

Living organisms have evolved over millions of years to fine tune their metabolism to create efficient pathways for producing metabolites necessary for their survival. Advancement in the field of synthetic biology has enabled the exploitation of these metabolic pathways for the production of desired compounds by creating microbial cell factories through metabolic engineering, thus providing sustainable routes to obtain value-added chemicals. Following the past success in metabolic engineering, there is increasing interest in diversifying natural metabolic pathways to construct non-natural biosynthesis routes, thereby creating possibilities for producing novel valuable compounds that are non-natural or without elucidated biosynthesis pathways. Thus, the range of chemicals that can be produced by biological systems can be expanded to meet the demands of industries for compounds such as plastic precursors and new antibiotics, most of which can only be obtained through chemical synthesis currently. Herein, we review and discuss novel strategies that have been developed to rewrite natural metabolic blueprints in a bid to broaden the chemical repertoire achievable in microorganisms. This review aims to provide insights on recent approaches taken to open new avenues for achieving biochemical production that are beyond currently available inventions.

The effect of electron density in furan pendant group on thermal-reversible Diels-Alder reaction based self-healing properties of polymethacrylate derivatives.

Herein, we discuss the effect of electron density in a furan pendant group on the thermally reversible Diels-Alder (DA) reaction based self-healing efficiency in polymethacrylate derivatives. First, the furan-functionalized polymethacrylates (rPFMA and dPFMA) having different electron density in the furan pendant groups were prepared through free-radical polymerization. The healing efficiency of rPFMA, which was expected to have high healing efficiency due to the high reactivity of DA reaction originating from the electron density in the furan moiety, was shown to be 95.89% in the first and 69.86% in the second healing process, respectively, where it is higher than that of dPFMA having relatively low electron density in the furan moiety. To illustrate these results, kinetic tests of the DA reaction for rPFMA64 and dPFMA64 were performed, where the reactivity of the DA reaction for rPFMA64 was much higher than that for dPFMA64. This could be explained by the electron density in the furan pendant groups which controls the reactivity of DA reaction having a major effect on the efficiency of self-healing performance in furan-functionalized polymethacrylates.

Effective therapeutic approach for head and neck cancer by an engineered minibody targeting the EGFR receptor.

Cetuximab, a chimeric monoclonal antibody developed for targeting the Epidermal Growth Factor Receptor (EGFR), has been intensively used to treat cancer patients with metastatic colorectal cancer and head and neck cancer. Intact immunoglobulin G (IgG) antibody like cetuximab, however, has some limitations such as high production cost and low penetration rate from vasculature into solid tumor mass due to its large size. In attempt to overcome these limitations, we engineered cetuximab to create single chain variable fragments (scFv-CH3; Minibody) that were expressed in bacterial system. Among three engineered minibodies, we found that MI061 minibody, which is composed of the variable heavy (VH) and light (VL) region joined by an 18-residue peptide linker, displays higher solubility and better extraction properties from bacterial lysate. In addition, we validated that purified MI061 significantly interferes ligand binding to EGFR and blocks EGFR's phosphorylation. By using a protein microarray composed of 16,368 unique human proteins covering around 2,400 plasma membrane associated proteins such as receptors and channels, we also demonstrated that MI061 only recognizes the EGFR but not other proteins as compared with cetuximab. These results indicated that engineered MI061 retains both binding specificity and affinity of cetuximab for EGFR. Although it had relatively short half-life in serum, it was shown to be highly significant anti-tumor effect by inhibiting ERK pathway in A431 xenograft model. Taken together, our present study provides compelling evidence that engineered minibody is more effective and promising agent for in vivo targeting of solid tumors.

Effects of the temporary placement of a self-expandable metallic stent in benign pyloric stenosis.

BACKGROUND/AIMS: The use of self-expandable metallic stents (SEMS) is an established palliative treatment for malignant stenosis in the gastrointestinal tract; therefore, its application to benign stenosis is expected to be beneficial because of the more gradual and sustained dilatation in the stenotic portion. We aimed in this prospective observational study to evaluate the efficacy and safety of temporary SEMS placement in benign pyloric stenosis. METHODS: Twenty-two patients with benign stenosis of the prepylorus, pylorus, and duodenal bulb were enrolled and underwent SEMS placement. We assessed symptom improvement, defined as an increase of at least 1 degree in the gastric-outlet-obstruction scoring system after stent insertion. RESULTS: No major complications were observed during the procedures. After stent placement, early symptom improvement was achieved in 18 of 22 patients (81.8%). During the follow-up period (mean 10.2 months), the stents remained in place successfully for 6 to 8 weeks in seven patients (31.8%). Among the 15 patients (62.5%) with stent migration, seven (46.6%) showed continued symptomatic improvement without recurrence of obstructive symptoms. CONCLUSIONS: Despite the symptomatic improvement, temporary SEMS placement is premature as an effective therapeutic tool for benign pyloric stenosis unless a novel stent is developed to prevent migration.

[Clinicopathologic feature of esophageal submucosal tumors treated by surgical approach].

BACKGROUND/AIMS: Submucosal tumors of the esophagus are rare lesions among all esophageal neoplasms. The purpose of this study was to evaluate the clinicopathologic features of esophageal submucosal tumors treated by surgical approach. METHODS: We analyzed the clinicopathologic and endoscopic ultrasonographic features of 18 esophageal submucosal tumors which were treated by surgical approach at Boramae Medical Center and Seoul National University Bundang Hospital from January 2005 to June 2012. RESULTS: The mean age was 48.9 years old and male to female ratio was 2.6 : 1. Asymptomatic patients were most common (77.8%). In endoscopic ultrasonographic finding, the majority tumor arouse in the middle (55.6%) and lower (44.4%) esophagus, and appeared as hypoechoic lesion (72.2%) in the 4th layer (83.3%). The most common indication for surgical approach was unclear biological behavior of the tumor. Minimally-invasive technique using thoracoscopy was applied for the enucleation (83.3%). The mean diameter of the tumor was 5.4 cm, and the final diagnosis was leiomyoma (89.9%) and gastrointestinal stromal tumor (11.1%). CONCLUSIONS: Leiomyoma was the most common submucosal tumor in esophagus. However, endoscopic ultrasonography was not able to differentiate between leiomyoma and gastrointesinal stromal tumor. For more accurate diagnosis and treatment, minimally-invasive approaches may be suitable for the surgical enucleation of indicated esophageal submucosal tumor.

A case of giant inflammatory ileal polyp removed by double-balloon enteroscopy.

Inflammatory fibroid polyps are rare benign tumors of the GI tract, that commonly present with intestinal obstruction as a result of intussusceptions in the small bowel. A 39-year old man visited our clinic with an asymptomatic polypoid mass in the distal ileum that was identified on abdominal computed tomography for postoperative surveillance after total gastrectomy due to previously diagnosed early gastric cancer. Retrograde double-balloon enteroscopy was performed to diagnose the ileal mass and a complete resection of the polyp was performed using snare for polypectomy without complications. The final histological finding was an ileal inflammatory polyp. Balloon-assisted enteroscopy is a valuable modality to diagnose and treat small bowel lesions in lieu of surgical procedures in selected cases.

[A case of hypopharyngeal cancer treated by endoscopic submucosal dissection].

Recent advances in endoscopic instruments, including narrow-band imaging (NBI) and magnification endoscopy, allowed dramatic increase in the early diagnosis of hypopharyngeal cancers. In addition, endoscopic mucosal resection or endoscopic submucosal dissection has recently been used for the treatment of hypopharyngeal cancer at an early stage, especially in Japan. However, to date, there is no published report in Korea. A 68-year-old man was admitted for preoperative evaluation and treatment for known esophageal cancer initially diagnosed at a local clinic. During the evaluation, magnifying endoscopy combined with the NBI system revealed a concurrent hypopharyngeal cancer not detected by initial conventional endoscopy. In this case report, we describe for the first time in Korea a case of early stage hypopharyngeal carcinoma that was successfully treated by endoscopic submucosal dissection with a review of literature.

Ethanol production from biodiesel-derived crude glycerol by newly isolated Kluyvera cryocrescens.

The rapidly expanding market for biodiesel has increased the supply and reduced the cost of glycerol, making it an attractive sustainable feed stock for the fuel and chemical industry. Glycerol-based biorefinery is the microbial fermentation of crude glycerol to produce fuels and chemicals. A major challenge is to obtain microbes tolerant to inhibitors such as salts and organic solvents present in crude glycerol. Microbial screening was attempted to isolate novel strain capable of growing on crude glycerol as a sole carbon source. The newly isolated bacteria, identified as nonpathogenic Kluyvera cryocrescens S26 could convert biodiesel-derived crude glycerol to ethanol with high yield and productivity. The supplementation of nutrients such as yeast extract resulted in distinguished enhancement in cell growth as well as ethanol productivity under anaerobic condition. When glycerol fermentation is performed under microaerobic condition, there is also a remarkable improvement in cell growth, ethanol productivity and yield, compared with those under strict anaerobic condition. In batch fermentation under microaerobic condition, K. cryocrescens S26 produced 27 g/l of ethanol from crude glycerol with high molar yield of 80% and productivity of 0.61 g/l/h.

Biotechnological production of enantiopure epoxides by enzymatic kinetic resolution.

Enantiopure epoxides are high value-added synthons for the production of pharmaceuticals, agrochemicals, as well as versatile fine chemicals and have broad scope of market demand for their applications. A major challenge in conventional organic synthesis is to generate such compounds in high enantiopurity with reasonable yield. Among possible chemical and biological technologies for enantiopure epoxide preparation, enzymatic kinetic resolution has been paid much attention with respect to its high enantioselectivity. Epoxide hydrolase (EH) has shown promising characteristics for the preparation of enantiopure epoxides and vicinal diols during enantioselective hydrolysis of racemic epoxides. EH is readily available from microbial resources thus it is being employed for biohydrolysis of a variety of epoxides. Recent technical progress in EH-catalyzed enantioselective hydrolysis is summarized in terms of exploration of novel EH, its functional improvement, high throughput assay, and preparative scale resolution process.

DO-stat fed-batch production of 2-keto-D-gluconic acid from cassava using immobilized Pseudomonas aeruginosa.

Bioconversion of cassava-derived glucose to 2-keto-D-gluconic acid (2-KDG) using resting cells of immobilized Pseudomonas aeruginosa IFO 3448 was investigated. The tuberous roots of cassava were selected as the feedstock as they are inexpensive and widely available, and possess high amounts of starch (approximately 70% (w/w) of dry mass). Immobilized bacteria was used in a fed-batch fermenter and recycled over a period of 2 weeks. Given that the formation of 2-KDG from glucose requires oxygen as a reagent, and that high glucose concentrations are detrimental to the production yield of 2-KDG by resting cells, a DO-stat control strategy was used, whereby the feed rate of cassava hydrolysate was regulated by coupling it with the control variable, dissolved oxygen. For 319 h of operation including three cycles of repeated fed batch, 72 g of 2-KDG was produced from hydrolysate derived from 110 g of dried cassava at a maximum production rate of 0.55 g/L/h and an average concentration of 35 g/L.

Production of (R)-ethyl-3,4-epoxybutyrate by newly isolated Acinetobacter baumannii containing epoxide hydrolase.

Several new microorganisms have been isolated from soil samples with high epoxide hydrolase activity toward ethyl 3,4-epoxybutyrate. Screening was performed by enrichment culture on alkenes as sole carbon source, followed by chiral gas chromatography. Eight strains were discovered with enantioselectivity from moderate to high level and identified as bacterial and yeast species. Cells were cultivated under aerobic condition at 30 degrees C using glucose as carbon source and resting cells were used as biocatalysts for kinetic resolution of ethyl 3,4-epoxybutyrate. Among isolated microorganisms, Acinetobacter baumannii showed highest enantioselectivity for (S)-enantiomer, resulting in (R)-ethyl-3,4-epoxybutyrates (>99%ee, 46% yield). It is the first report on the fact that epoxide hydrolases originating from bacterial species of A. baumannii was applied to kinetic resolution of ethyl 3,4-epoxybutyrate in order to obtain enantiopure high-value-added (R)-ethyl-3,4-epoxybutyrate.

Mung bean lipoxygenase in the production of a C6-aldehyde. Natural green-note flavor generation via biotransformation.

Mung bean was investigated as a novel source of lipoxygenase in the natural production of the green-note aroma compound hexanal. Lipoxygenase extracted from mung bean catalyzed the oxidative reaction of linoleic acid, after which the intermediate hydroperoxide compound was split via green bell pepper hydroperoxide lyase to produce hexanal. In comparison to soybean lipoxygenase, mung bean lipoxygenase was found to be a good substitute as it produced 15.4 mM (76% yield) hexanal while soybean gave 60% yield. The mung bean pH profile comprised a wide peak (optimum pH 6.5) representing lipoxygenase-2 and lipoxygenase-3 isozymes, whereas two narrower peaks representing lipoxygenase-1 and lipoxygenase-2/3 isozymes were observed for soybean (optimum pH 10). Extraction at pH 4.5 was preferred, at which specific lipoxygenase activity was also the highest.

Improvement in extraction and catalytic activity of Mucor javanicus lipase by modification of AOT reverse micelle.

Reverse micelles are formed in apolar solvents by spontaneous aggregation of surfactants. Surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) is most often used for the reverse micellar extraction of enzymes. However, the inactivation of enzyme due to strong interaction with AOT molecules is a severe problem. To overcome this problem, the AOT/water/isooctane reverse micellar system was modified by adding short chain polyethylene glycol 400 (PEG 400). The modified AOT reverse micellar system was used to extract Mucor javanicus lipase from the aqueous phase to the reverse micellar phase. The extraction efficiency (E) increased with the increase in PEG 400 addition and the maximum E in PEG 400 modified system was twofold higher than that in the PEG 400-free system. Upon addition of PEG 400, the water activity (a(w)) of aqueous phase decreased, whereas a(w) of reverse micellar phase increased. The circular dichroism spectroscopy analysis revealed that PEG 400 changes the secondary and tertiary structure of lipase. The maximum specific activity of lipase extracted in PEG 400-modified reverse micellar system was threefold higher than that in the PEG-free system.