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Waste to Energy: Steam explosion-based torrefaction process to produce solid biofuel for power generation utilizing various waste biomasses. BIORESOURCE TECHNOLOGY 2024; 394:130185. [PMID: 38072073 DOI: 10.1016/j.biortech.2023.130185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 12/06/2023] [Accepted: 12/06/2023] [Indexed: 02/04/2024]
Abstract
Currently, humankind is facing a serious environmental and climate crisis, which has accelerated the research on producing bioenergy from waste biomass as a carbon-neutral feedstock. In this study, the aim was to develop an upcycling strategy for waste biomass to solid-type biofuel conversion for power generation. Various types of waste biomass (i.e., waste wood after lumbering, sawdust-type mushroom waste wood, kudzu vine, and empty fruit bunches from palm) were used as sustainable feedstocks for steam explosion-based torrefaction. The reaction conditions were optimized for each waste biomass by controlling the severity index (Ro); the higher heating value increased proportional to the Ro increase. Additionally, component analysis revealed that steam explosion torrefaction mainly degraded hemicellulose, and most of the torrefied waste biomass met the Bio-Solid Refuse Fuel quality standard. The results provide not only a viable waste-to-energy strategy but also insights to address global climate change.
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Synergetic effect of lytic polysaccharide monooxygenase from Thermobifida fusca on saccharification of agrowastes. BIORESOURCE TECHNOLOGY 2023; 378:129015. [PMID: 37019417 DOI: 10.1016/j.biortech.2023.129015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 03/30/2023] [Accepted: 04/03/2023] [Indexed: 06/19/2023]
Abstract
Saccharification is one of the most noteworthy processes in biomass-based biorefineries. In particular, the lytic polysaccharide monooxygenase has recently emerged as an oxidative cleavage-recalcitrant polysaccharide; however, there is insufficient information regarding its application to actual biomass. Accordingly, this study focused optimizing the recombinant expression level of a bacterial lytic polysaccharide monooxygenase from Thermobifida fusca (TfLPMO), which was characterized as a cellulolytic enzyme. Finally, the synergistic effect of the lytic polysaccharide monooxygenase and a commercial cellulase cocktail on the saccharification of agrowaste was investigated. TfLPMO functioned on various cellulosic and hemicellulosic substrates, and the combination of TfLPMO with cellulase exhibited a synergistic effect on the saccharification of agrowastes, resulting in a 19.2% and 14.1% increase in reducing sugars from rice straw and corncob, respectively. The results discussed herein can lead to an in-depth understanding of enzymatic saccharification and suggest viable options for valorizing agrowastes as renewable feedstocks in biorefineries.
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Development of bioprocess for corncob-derived levulinic acid production. BIORESOURCE TECHNOLOGY 2023; 371:128628. [PMID: 36646357 DOI: 10.1016/j.biortech.2023.128628] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 01/10/2023] [Accepted: 01/12/2023] [Indexed: 06/17/2023]
Abstract
Levulinic acid is a significant platform chemical obtained from biomass and can potentially be used to produce value-added biofuels, biopolymers, and biopharmaceuticals. This study aims at statistically optimizing levulinic acid production from agrowastes. Based on the total carbohydrate content (71.93 %), corncob was selected as the target feedstock. A Box-Behnken design with four factors, such as feedstock concentration, reaction time, reaction temperature, and catalyst concentration, was used to optimize the hydrothermal conversion of corncob to levulinic acid at 180 °C for 30 min using 1 M H2SO4 as the acid catalyst and 120 g/L corncob. The maximum yield of 19.9 % was obtained. Additionally, 8.1 g/L formic acid was co-produced. The results of this study can contribute toward valorization of levulinic acid. Moreover, our results can be useful in developing strategies to utilize agrowastes as a renewable feedstock for recent biorefineries to cope with the climate crisis.
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Bifidobacterium species BB_003 enhances antitumor immunity in patients with NMIBC and improve recurrence-free survival. Eur Urol 2023. [DOI: 10.1016/s0302-2838(23)00656-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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5
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Rice straw-derived lipid production by HMF/furfural-tolerant oleaginous yeast generated by adaptive laboratory evolution. BIORESOURCE TECHNOLOGY 2023; 367:128220. [PMID: 36328172 DOI: 10.1016/j.biortech.2022.128220] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/22/2022] [Accepted: 10/25/2022] [Indexed: 06/16/2023]
Abstract
Research on producing medium- and long-chain hydrocarbons as drop-in biofuels has recently accelerated. In addition, lipids are emerging as precursors for biofuel production, and thus, microbial lipid production utilizing agrowastes is becoming a feasible platform technology. Nonetheless, microorganisms are often inhibited by furan aldehydes in biomass-derived hydrolysates. Accordingly, this study aimed to develop oleaginous yeast strains that can tolerate furan aldehydes for producing lipids as biofuel precursors. Rhodosporidium toruloides was selected as the target for adaptive laboratory evolution. The evolved strain, which was obtained from 16 rounds of subcultures, showed a 2.5-fold higher specific growth rate than the wild-type strain in the presence of furan aldehydes and slightly higher lipid production in rice straw hydrolysate. The results discussed in this study provide insights into the production of lipid production by oleaginous yeast utilizing agrowastes as feedstock to obtain drop-in biofuels and contribute to feasible strategies to address climate crises.
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Valorization of CO 2 to β-farnesene in Rhodobacter sphaeroides. BIORESOURCE TECHNOLOGY 2022; 363:127955. [PMID: 36115510 DOI: 10.1016/j.biortech.2022.127955] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/06/2022] [Accepted: 09/08/2022] [Indexed: 06/15/2023]
Abstract
The valorization of CO2 into valuable products is a sustainable strategy to help overcome the climate crisis. In particular, biological conversion is attractive as it can produce long-chain hydrocarbons such as terpenoids. This study reports the high yield of β-farnesene production from CO2 by expressing heterologous β-farnesene synthase (FS) into Rhodobacter sphaeroides. To increase the expression of FS, a strong active promoter and a ribosome binding site (RBS) were engineered. Moreover, β-farnesene production was improved further through the supply of exogenous antioxidants and additional nutrients. Finally, β-farnesene was produced from CO2 at a titer of 44.53 mg/L and yield of 234.08 mg/g, values that were correspondingly 23 times and 46 times higher than those from the initial production of β-farnesene. Altogether, the results here suggest that the autotrophic production of β-farnesene can provide a starting point for achieving a circular carbon economy.
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Lytic polysaccharide monooxygenase (LPMO)-derived saccharification of lignocellulosic biomass. BIORESOURCE TECHNOLOGY 2022; 359:127501. [PMID: 35753567 DOI: 10.1016/j.biortech.2022.127501] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 06/14/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
Given that traditional biorefineries have been based on microbial fermentation to produce useful fuels, materials, and chemicals as metabolites, saccharification is an important step to obtain fermentable sugars from biomass. It is well-known that glycosidic hydrolases (GHs) are responsible for the saccharification of recalcitrant polysaccharides through hydrolysis, but the discovery of lytic polysaccharide monooxygenase (LPMO), which is a kind of oxidative enzyme involved in cleaving polysaccharides and boosting GH performance, has profoundly changed the understanding of enzyme-based saccharification. This review briefly introduces the classification, structural information, and catalytic mechanism of LPMOs. In addition to recombinant expression strategies, synergistic effects with GH are comprehensively discussed. Challenges and perspectives for LPMO-based saccharification on a large scale are also briefly mentioned. Ultimately, this review can provide insights for constructing an economically viable lignocellulose-based biorefinery system and a closed-carbon loop to cope with climate change.
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Recombinant expression and characterization of formate dehydrogenase from Clostridium ljungdahlii (ClFDH) as CO2 reductase for converting CO2 to formate. J CO2 UTIL 2022. [DOI: 10.1016/j.jcou.2021.101876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Newly explored formate dehydrogenases from Clostridium species catalyze carbon dioxide to formate. BIORESOURCE TECHNOLOGY 2022; 348:126832. [PMID: 35149183 DOI: 10.1016/j.biortech.2022.126832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 02/03/2022] [Accepted: 02/04/2022] [Indexed: 06/14/2023]
Abstract
With concerns over global warming and climate change, many efforts have been devoted to mitigate atmospheric CO2 level. As a CO2 utilization strategy, formate dehydrogenase (FDH) from Clostridium species were explored to discover O2-tolerant and efficient FDHs that can catalyze CO2 to formate (i.e. CO2 reductase). With FDH from Clostridium ljungdahlii (ClFDH) that plays as a CO2 reductase previously reported as the reference, FDH from C.autoethanogenum (CaFDH), C. coskatii (CcFDH), and C. ragsdalei (CrFDH) were newly discovered via genome-mining. The FDHs were expressed in Escherichia coli and the recombinant FDHs successfully catalyzed CO2 reduction with a specific activity of 15 U g-1-CaFDH, 17 U g-1-CcFDH, and 8.7 U g-1-CrFDH. Interestingly, all FDHs newly discovered retain their catalytic activity under aerobic condition, although Clostridium species are strict anaerobe. The results discussed herein can contribute to biocatalytic CO2 utilization.
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Paradigm shift in algal biomass refinery and its challenges. BIORESOURCE TECHNOLOGY 2022; 346:126358. [PMID: 34800638 DOI: 10.1016/j.biortech.2021.126358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 11/10/2021] [Accepted: 11/11/2021] [Indexed: 06/13/2023]
Abstract
Microalgae have been studied and tested for over 70 years. However, biodiesel, the prime target of the algal industry, has suffered from low competitiveness and current steps toward banning the internal combustion engine all over the world. Meanwhile, interest in reducing CO2 emissions has grown as the world has witnessed disasters caused by global warming. In this situation, in order to maximize the benefits of the microalgal industry and surmount current limitations, new breakthroughs are being sought. First, drop-in fuel, mandatory for the aviation and maritime industries, has been discussed as a new product. Second, methods to secure stable and feasible outdoor cultivation focusing on CO2 sequestration were investigated. Lastly, the need for an integrated refinery process to simultaneously produce multiple products has been discussed. While the merits of microalgae industry remain valid, further investigations into these new frontiers would put algal industry at the core of future bio-based economy.
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Effect of manganese peroxidase on the decomposition of cellulosic components: Direct cellulolytic activity and synergistic effect with cellulase. BIORESOURCE TECHNOLOGY 2022; 343:126138. [PMID: 34678456 DOI: 10.1016/j.biortech.2021.126138] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 10/09/2021] [Accepted: 10/12/2021] [Indexed: 06/13/2023]
Abstract
Herein, it was unearthed that manganese peroxidase (MnP) from Phanerochaete chrysosporium, a lignin-degrading enzyme, is capable of not only directly decomposing cellulosic components but also boosting cellulase activity. MnP decomposes various cellulosic substrates (carboxymethyl cellulose, cellobiose [CMC], and Avicel®) and produces reducing sugars rather than oxidized sugars such as lactone and ketoaldolase. MnP with MnII in acetate buffer evolves the MnIII-acetate complex functioning as a strong oxidant, and the non-specificity of MnIII-acetate enables cellulose-decomposition. The catalytic mechanism was proposed by analyzing catalytic products derived from MnP-treated cellopentaose. Notably, MnP also boosts cellulase activity on CMC and Avicel®, even considering the cellulolytic activity of MnP itself. To the best of the authors' knowledge, this is the first report demonstrating a previously unknown fungal MnP activity in cellulose-decomposition in addition to a known delignification activity. Consequently, the results provide a promising insight for further investigation of the versatility of lignin-degrading biocatalysts.
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Recent progress and challenges in microbial polyhydroxybutyrate (PHB) production from CO 2 as a sustainable feedstock: A state-of-the-art review. BIORESOURCE TECHNOLOGY 2021; 339:125616. [PMID: 34304096 DOI: 10.1016/j.biortech.2021.125616] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/14/2021] [Accepted: 07/16/2021] [Indexed: 05/05/2023]
Abstract
The recalcitrance of petroleum-based plastics causes severe environmental problems and has accelerated research into production of biodegradable polymers from inexpensive and sustainable feedstocks. Various microorganisms are capable of producing Polyhydroxybutyrate (PHB), a representative biodegradable polymer, under nutrient-limited conditions, among which CO2-utilizing microorganisms are of primary interest. Herein, we discuss recent progress on bacterial strains including proteobacteria, purple non-sulfur bacteria, and cyanobacteria in terms of CO2-containing carbon sources, PHB-production capability, and genetic modification. In addition, this review introduces recent technical approaches used to improve PHB production from CO2 such as two-stage bioprocesses and bioelectrochemical systems. Challenges and future perspectives for the development of economically feasible PHB production are also discussed. Finally, this review might provide insights into the construction of a closed-carbon-loop to cope with climate change.
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Improving the catalytic performance of xylanase from Bacillus circulans through structure-based rational design. BIORESOURCE TECHNOLOGY 2021; 340:125737. [PMID: 34426235 DOI: 10.1016/j.biortech.2021.125737] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 08/03/2021] [Accepted: 08/05/2021] [Indexed: 06/13/2023]
Abstract
Endo-1,4-β-xylanase is one of the most important enzymes employed in biorefineries for obtaining fermentable sugars from hemicellulosic components. Herein, we aimed to improve the catalytic performance of Bacillus circulans xylanase (Bcx) using a structure-guided rational design. A systematic analysis of flexible motions revealed that the R49 component of Bcx (i) constrains the global conformational changes essential for substrate binding and (ii) is involved in modulating flexible motion. Site-saturated mutagenesis of the R49 residue led to the engineering of the active mutants with the trade-off between flexibility and rigidity. The most active mutant R49N improved the catalytic performance, including its catalytic efficiency (7.51-fold), conformational stability (0.7 °C improvement), and production of xylose oligomers (2.18-fold higher xylobiose and 1.72-fold higher xylotriose). The results discussed herein can be applied to enhance the catalytic performance of industrially important enzymes by controlling flexibility.
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Improving the organic solvent resistance of lipase a from Bacillus subtilis in water-ethanol solvent through rational surface engineering. BIORESOURCE TECHNOLOGY 2021; 337:125394. [PMID: 34134054 DOI: 10.1016/j.biortech.2021.125394] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/04/2021] [Accepted: 06/06/2021] [Indexed: 06/12/2023]
Abstract
Given that lipase is an enzyme applicable in various industrial fields and water-miscible organic solvents are important reaction media for developing industrial-scale biocatalysis, a structure-based strategy was explored to stabilize lipase A from Bacillus subtilis in a water-ethanol cosolvent. Site-directed mutagenesis of ethanol-interacting sites resulted in 4 mutants, i.e., Ser16Gly, Ala38Gly, Ala38Thr, and Leu108Asn, which were stable in 50% ethanol and had up to 1.8-fold higher stability than the wild-type. In addition, Leu108Asn was more thermostable at 45 °C than the wild type. The results discussed in this study not only provide insights into strategies for enzyme engineering to improve organic solvent resistance but also suggest perspectives on pioneering routes for constructing enzyme-based biorefineries to produce value-added fuels and chemicals.
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Chemoenzymatic valorization of agricultural wastes into 4-hydroxyvaleric acid via levulinic acid. BIORESOURCE TECHNOLOGY 2021; 337:125479. [PMID: 34320759 DOI: 10.1016/j.biortech.2021.125479] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 06/23/2021] [Accepted: 06/26/2021] [Indexed: 06/13/2023]
Abstract
Given that (i) levulinic acid (LA) is one of the most significant platform chemicals derived from biomass and (ii) 4-hydroxyvaleric acid (4-HV) is a potential LA derivative, the aim of this study is to achieve chemoenzymatic valorization of LA, which was obtained from agricultural wastes, to 4-HV. The thermochemical process utilized agricultural wastes (i.e., rice straw and corncob) as feedstocks and successfully produced LA, ranging from 25.1 to 65.4 mM. Additionally, formate was co-produced and used as a hydrogen source for the enzymatic hydrogenation of LA. Finally, engineered 3-hydroxybutyrate dehydrogenase from Alcaligenes faecalis (eHBDH) was applicable for catalyzing the conversion of agricultural wastes-driven LA, resulting in a maximum concentration of 11.32 mM 4-HV with a conversion rate of 48.2%. To the best of our knowledge, this is the first report describing the production of 4-HV from actual biomass, and the results might provide insights into the valorization of agricultural wastes.
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Recent developments and key barriers to microbial CO 2 electrobiorefinery. BIORESOURCE TECHNOLOGY 2021; 320:124350. [PMID: 33186841 DOI: 10.1016/j.biortech.2020.124350] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 10/25/2020] [Accepted: 10/27/2020] [Indexed: 06/11/2023]
Abstract
The electrochemical conversion of CO2 can include renewable surplus electricity storage and CO2 utilisation. This review focuses on the microbial CO2 electrobiorefinery based on microbial electrosynthesis (MES) which merges electrochemical and microbial conversion to produce biofuels and higher-value chemicals. In this review, recent developments are discussed about bioelectrochemical conversion of CO2 into biofuels and chemicals in MES via microbial CO2-fixation and electricity utilisation reactions. In addition, this review examines technical approaches to overcome the current limitations of MES including the following: engineering of the biocathode, application of electron mediators, and reactor optimisation, among others. An in-depth discussion of strategies for the CO2 electrobiorefinery is presented, including the integration of the biocathode with inorganic catalysts, screening of novel electroactive microorganisms, and metabolic engineering to improve target productivity from CO2.
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Recent progress in formate dehydrogenase (FDH) as a non-photosynthetic CO2 utilizing enzyme: A short review. J CO2 UTIL 2020. [DOI: 10.1016/j.jcou.2020.101353] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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064 Attitude of Women Nurse Practitioners for Embarrassing Female Sexual and Urinary Symptoms in Korea. J Sex Med 2020. [DOI: 10.1016/j.jsxm.2020.04.300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Elevated conversion of CO 2 to versatile formate by a newly discovered formate dehydrogenase from Rhodobacter aestuarii. BIORESOURCE TECHNOLOGY 2020; 305:123155. [PMID: 32178996 DOI: 10.1016/j.biortech.2020.123155] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/02/2020] [Accepted: 03/04/2020] [Indexed: 06/10/2023]
Abstract
Due to climate change, recent research interests have increased towards CO2 utilization as a strategy to mitigate the atmospheric CO2 level. Herein, we aimed to explore formate dehydrogenases (FDHs) from chemoautotroph to discover an efficient and O2-tolerant biocatalyst for catalyzing the CO2 reduction to a versatile formate. Through genome-mining and phylogenetic analysis, the FDH from Rhodobacter aestuarii (RaFDH) was newly discovered as a promising O2-tolernat CO2 reductase and was successfully expressed in Escherichia coli. In this study, the optimum conditions and turnover rates of RaFDH were examined for CO2 reduction and formate oxidation. In particular, the RaFDH-driven CO2 reduction far surpassed the formate oxidation with a turnover rate of 48.3 and 15.6 min-1, respectively. The outstanding superiority of RaFDH towards CO2 reduction can be applicable for constructing a feasible electroenzymatic system that produce a versatile formate from CO2 as a cheap, abundant, and renewable resource.
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199 Attitude of Women Nurses for Embarrassing Female Sexual and Urinary Symptoms in Korea. J Sex Med 2020. [DOI: 10.1016/j.jsxm.2019.11.196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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A perspective on the biotechnological applications of the versatile tyrosinase. BIORESOURCE TECHNOLOGY 2019; 289:121730. [PMID: 31279520 DOI: 10.1016/j.biortech.2019.121730] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 06/09/2023]
Abstract
Tyrosinase (E.C. 1.14.18. 1) is a type of Cu-containing oxidoreductase which has bifunctional activity for various phenolic substrates: ortho-hydroxylation of monophenols to diphenols (a cresolase activity) and oxidation of diphenols to quinones (a catecholase activity). Based on the broad substrate spectrum, tyrosinase has been used in bioremediation of phenolic pollutants, constructing biosensors for identifying phenolic compounds, and L-DOPA synthesis. Furthermore, not only tyrosinase has been used to produce useful polyphenol derivatives, but also it is recently revealed that the promiscuous activity of tyrosinase is closely related with delignification in the biorefinery. Accordingly, tyrosinase might be a potential biocatalyst for industrial applications (e.g., electroenzymatic L-DOPA production, but its long-term stability and reusability should be further explored. In this review, we emphasize the versatility of tyrosinase, which includes conventional applications, and suggest new perspectives as an industrial biocatalyst (e.g., electroenzymatic L-DOPA production). Especially, this review focuses on and comprehensively discusses recent innovative studies.
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22
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418 The relationship between premature ejaculation and lower urinary tract symptoms in mid to old men. J Sex Med 2018. [DOI: 10.1016/j.jsxm.2018.04.324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Value of unenhanced MRI with diffusion-weighted imaging for detection of primary small (≤20 mm) solid pancreatic tumours and prediction of pancreatic ductal adenocarcinoma. Clin Radiol 2017; 72:1076-1084. [DOI: 10.1016/j.crad.2017.07.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 06/27/2017] [Accepted: 07/12/2017] [Indexed: 02/07/2023]
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Perspectives for biocatalytic lignin utilization: cleaving 4- O-5 and C α-C β bonds in dimeric lignin model compounds catalyzed by a promiscuous activity of tyrosinase. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:212. [PMID: 28912833 PMCID: PMC5594458 DOI: 10.1186/s13068-017-0900-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 09/05/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND In the biorefinery utilizing lignocellulosic biomasses, lignin decomposition to value-added phenolic derivatives is a key issue, and recently biocatalytic delignification is emerging owing to its superior selectivity, low energy consumption, and unparalleled sustainability. However, besides heme-containing peroxidases and laccases, information about lignolytic biocatalysts is still limited till date. RESULTS Herein, we report a promiscuous activity of tyrosinase which is closely associated with delignification requiring high redox potentials (>1.4 V vs. normal hydrogen electrode [NHE]). The promiscuous activity of tyrosinase not only oxidizes veratryl alcohol, a commonly used nonphenolic substrate for assaying ligninolytic activity, to veratraldehyde but also cleaves the 4-O-5 and Cα-Cβ bonds in 4-phenoxyphenol and guaiacyl glycerol-β-guaiacyl ether (GGE) that are dimeric lignin model compounds. Cyclic voltammograms additionally verified that the promiscuous activity oxidizes lignin-related high redox potential substrates. CONCLUSION These results might be applicable for extending the versatility of tyrosinase toward biocatalytic delignification as well as suggesting a new perspective for sustainable lignin utilization. Furthermore, the results provide insight for exploring the previously unknown promiscuous activities of biocatalysts much more diverse than ever thought before, thereby innovatively expanding the applicable area of biocatalysis.
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Expression and characterization of Pantoea CO dehydrogenase to utilize CO-containing industrial waste gas for expanding the versatility of CO dehydrogenase. Sci Rep 2017; 7:44323. [PMID: 28290544 PMCID: PMC5349547 DOI: 10.1038/srep44323] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/06/2017] [Indexed: 12/02/2022] Open
Abstract
Although aerobic CO dehydrogenases (CODHs) might be applicable in various fields, their practical applications have been hampered by low activity and no heterologous expression. We, for the first time, could functionally express recombinant PsCODH in E. coli and obtained a highly concentrated recombinant enzyme using an easy and convenient method. Its electron acceptor spectra, optimum conditions (pH 6.5 and 30 °C), and kinetic parameters (kcat of 12.97 s−1, Km of 0.065 mM, and specific activity of 0.86 Umg−1) were examined. Blast furnace gas (BFG) containing 20% CO, which is a waste gas from the steel-making process, was tested as a substrate for PsCODH. Even with BFG, the recombinant PsCODH retained 88.2% and 108.4% activity compared with those of pure CO and 20% CO, respectively. The results provide not only a promising strategy to utilize CO-containing industrial waste gases as cheap, abundant, and renewable resources but also significant information for further studies about cascade reactions producing value-added chemicals via CO2 as an intermediate produced by a CODH-based CO-utilization system, which would ultimately expand the versatility of CODH.
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Selective determination of dopamine with an amperometric biosensor using electrochemically pretreated and activated carbon/tyrosinase/Nafion®-modified glassy carbon electrode. BIOTECHNOL BIOPROC E 2016. [DOI: 10.1007/s12257-016-0382-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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An extended KRAS mutation test for the detection of 28 common mutations in FFPET and plasma specimens. Ann Oncol 2016. [DOI: 10.1093/annonc/mdw363.42] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Highly sensitive and selective dopamine detection by an amperometric biosensor based on tyrosinase/MWNT/GCE. KOREAN J CHEM ENG 2016. [DOI: 10.1007/s11814-016-0207-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Surgery for lumbar disc herniation: Analysis of 500 consecutive patients treated in an interdisciplinary spine centre. J Clin Neurosci 2016; 27:40-3. [PMID: 26778355 DOI: 10.1016/j.jocn.2015.08.038] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 08/18/2015] [Accepted: 08/21/2015] [Indexed: 11/25/2022]
Abstract
Surgical removal of a symptomatic herniated lumbar disc is performed either with or without the support of a microscope. Up to the time of writing, the literature has reported similar clinical outcomes for the two procedures. Five hundred consecutive patients, operated upon for primary single-level lumbar disc herniation in our University Spine Center between 2003-2011, with (n=275), or without (n=225), the aid of a microscope were included. Data were retrospectively analyzed, comparing the primary endpoint of clinical outcome and the secondary endpoints of complications, surgical time and length of hospitalization. Clinical outcomes and reoperation rates were comparable in both groups. Surgical time was significantly shorter with a mean time of 47minutes without use of the microscope compared to the mean time of 87minutes (p<0.001) with the use of the microscope. Mean length of hospitalization was shorter in those operated with the microscope (5.3days) compared to those without (6.1days, p=0.004). There was no difference in rates of complications. Microdiscectomy versus open sequestrectomy and discectomy for surgical treatment of lumbar disc herniation is associated with similar clinical outcomes and reoperation rates. Open sequestrectomy is associated with shorter operation times. Microdiscectomy is associated with shorter hospitalization stays.
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Novel NAD-independent d-lactate dehydrogenases from Acetobacter aceti and Acidocella species MX-AZ02 as potential candidates for in vitro biocatalytic pyruvate production. Biochem Eng J 2016. [DOI: 10.1016/j.bej.2015.10.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Environmental Exposure to Phthalates may Affect Bone Mineral Density in Older Women. Int J Epidemiol 2015. [DOI: 10.1093/ije/dyv096.225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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High sensitivity of contact-heat evoked potentials in “snake-eye” appearance myelopathy. Clin Neurophysiol 2015; 126:1994-2003. [DOI: 10.1016/j.clinph.2014.12.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Revised: 11/30/2014] [Accepted: 12/10/2014] [Indexed: 12/12/2022]
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Higher fibrinogen concentrations for reduction of transfusion requirements during major paediatric surgery: A prospective randomised controlled trial. Br J Anaesth 2015; 115:234-43. [PMID: 25982134 DOI: 10.1093/bja/aev136] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2015] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Hypofibrinogenaemia is one of the main reasons for development of perioperative coagulopathy during major paediatric surgery. The aim of this study was to assess whether prophylactic maintenance of higher fibrinogen concentrations through administration of fibrinogen concentrate would decrease the volume of transfused red blood cell (RBCs). METHODS In this prospective, randomised, clinical trial, patients aged 6 months to 17 yr undergoing craniosynostosis and scoliosis surgery received fibrinogen concentrate (30 mg kg(-1)) at two predefined intraoperative fibrinogen concentrations [ROTEM(®) FIBTEM maximum clot firmness (MCF) of <8 mm (conventional) or <13 mm (early substitution)]. Total volume of transfused RBCs was recorded over 24 h after start of surgery. RESULTS Thirty children who underwent craniosynostosis surgery and 19 children who underwent scoliosis surgery were treated per protocol. During craniosynostosis surgery, children in the early substitution group received significantly less RBCs (median, 28 ml kg(-1); IQR, 21 to 50 ml kg(-1)) compared with the conventional fibrinogen trigger of <8 mm (median, 56 ml kg(-1); IQR, 28 to 62 ml kg(-1)) (P=0.03). Calculated blood loss as per cent of estimated total blood volume decreased from a median of 160% (IQR, 110-190%) to a median of 90% (IQR, 78-110%) (P=0.017). No significant changes were observed in the scoliosis surgery population. No bleeding events requiring surgical intervention, postoperative transfusions of RBCs, or treatment-related adverse events were observed. CONCLUSIONS Intraoperative administration of fibrinogen concentrate using a FIBTEM MCF trigger level of <13 mm can be successfully used to significantly decrease bleeding, and transfusion requirements in the setting of craniosynostosis surgery, but not scoliosis. CLINICAL TRIAL REGISTRY NUMBER ClinicalTrials.gov NCT01487837.
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Electrochemical detoxification of phenolic compounds in lignocellulosic hydrolysate for Clostridium fermentation. BIORESOURCE TECHNOLOGY 2015; 187:228-234. [PMID: 25863199 DOI: 10.1016/j.biortech.2015.03.129] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 03/26/2015] [Accepted: 03/27/2015] [Indexed: 05/23/2023]
Abstract
Lignocellulosic biomass is being preferred as a feedstock in the biorefinery, but lignocellulosic hydrolysate usually contains inhibitors against microbial fermentation. Among these inhibitors, phenolics are highly toxic to butyric acid-producing and butanol-producing Clostridium even at a low concentration. Herein, we developed an electrochemical polymerization method to detoxify phenolic compounds in lignocellulosic hydrolysate for efficient Clostridium fermentation. After the electrochemical detoxification for 10h, 78%, 77%, 82%, and 94% of p-coumaric acid, ferulic acid, vanillin, and syringaldehyde were removed, respectively. Furthermore, 71% of total phenolics in rice straw hydrolysate were removed without any sugar-loss. Whereas the cell growth and metabolite production of Clostridium tyrobutyricum and Clostridium beijerinckii were completely inhibited in un-detoxified hydrolysate, those in detoxifying rice straw hydrolysate were recovered to 70-100% of the control cultures. The electrochemical detoxification method described herein provides an efficient strategy for producing butanol and butyric acid through Clostridium fermentation with lignocellulosic hydrolysate.
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Korean Medication Algorithm for Bipolar Disorder 2014. Eur Psychiatry 2015. [DOI: 10.1016/s0924-9338(15)30920-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Overview on the biotechnological production of L-DOPA. Appl Microbiol Biotechnol 2014; 99:575-84. [PMID: 25432672 DOI: 10.1007/s00253-014-6215-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Revised: 11/03/2014] [Accepted: 11/04/2014] [Indexed: 10/24/2022]
Abstract
L-DOPA (3,4-dihydroxyphenyl-L-alanine) has been widely used as a drug for Parkinson's disease caused by deficiency of the neurotransmitter dopamine. Since Monsanto developed the commercial process for L-DOPA synthesis for the first time, most of currently supplied L-DOPA has been produced by the asymmetric method, especially asymmetric hydrogenation. However, the asymmetric synthesis shows critical limitations such as a poor conversion rate and a low enantioselectivity. Accordingly, alternative biotechnological approaches have been researched for overcoming the shortcomings: microbial fermentation using microorganisms with tyrosinase, tyrosine phenol-lyase, or p-hydroxyphenylacetate 3-hydroxylase activity and enzymatic conversion by immobilized tyrosinase. Actually, Ajinomoto Co. Ltd commercialized Erwinia herbicola fermentation to produce L-DOPA from catechol. In addition, the electroenzymatic conversion system was recently introduced as a newly emerging scheme. In this review, we aim to not only overview the biotechnological L-DOPA production methods, but also to briefly compare and analyze their advantages and drawbacks. Furthermore, we suggest the future potential of biotechnological L-DOPA production as an industrial process.
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Semiautomatic superimposition improves radiological assessment of curve flexibility in scoliosis. Eur Radiol 2014; 25:860-4. [PMID: 25231133 DOI: 10.1007/s00330-014-3433-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Revised: 08/20/2014] [Accepted: 09/03/2014] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Assessment of scoliotic curve flexibility and stiffness is essential for planning surgical treatment in adolescent idiopathic scoliosis (AIS). Measurement of curve flexibility is currently insufficiently precise. The purpose of this study was to introduce and validate a novel method of superimposing radiographs for more reliable measurement of curve flexibility. MATERIAL AND METHODS Two independent radiologists measured Cobb angles separately on standard anterior-posterior (AP) (n = 48) and supine bending radiographs (n = 48), in patients with AIS, who were randomly included from a surgical database. The same readers repeated the measurements after the bending radiographs were semi-automatically superimposed on the AP radiographs by fusing the caudad end vertebra. Curve flexibility was calculated. Inter-reader agreement between the two independent readers was calculated using interclass correlation coefficient (ICC). RESULTS A moderate inter-reader agreement was achieved in the upper curve (ICC = 0.57) and a good agreement in the lower curve (ICC = 0.72) with the standard method of assessing curve flexibility. With the use of the semiautomatic superimposition, however, almost perfect agreement was achieved for both the upper and the lower curves flexibilities (ICC = 0.93 and 0.97, respectively). CONCLUSION The introduced semi-automatic superimposition technique for measurement of scoliotic curve flexibility in AIS is more precise and reliable than the current standard method.
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Decompression Surgery for Lumbar Spinal Canal Stenosis in Octogenarians; Single Center Experience of 121 Consecutive Cases. J Neurol Surg A Cent Eur Neurosurg 2014. [DOI: 10.1055/s-0034-1383766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Storage of apheresis platelet concentrates after manual replacement of >95% of plasma with PAS 5. Vox Sang 2014; 107:247-53. [DOI: 10.1111/vox.12157] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 04/08/2014] [Accepted: 04/09/2014] [Indexed: 12/01/2022]
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A Pleomorphic Carcinoma of the Lung with Small Intestinal Metastasis Producing Multiple Cytokines. Ann Oncol 2013. [DOI: 10.1093/annonc/mdt460.137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Red cell storage in E-Sol 5 and Adsol additive solutions: paired comparison using mixed and non-mixed study designs. Vox Sang 2013; 106:322-9. [DOI: 10.1111/vox.12108] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 09/30/2013] [Accepted: 10/04/2013] [Indexed: 11/30/2022]
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Abduction extension cervical nerve root stress test: anatomical basis and clinical relevance. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2013; 22:1522-1525. [PMID: 23412084 PMCID: PMC3698357 DOI: 10.1007/s00586-013-2689-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Revised: 11/28/2012] [Accepted: 01/25/2013] [Indexed: 06/01/2023]
Abstract
PURPOSE While the Lasègue straight leg raising test is an established test for lumbar nerve root compression, an established equivalent for cervical nerve root compression is missing. The aim of this bi-modal study was to find the most effective way to stretch the cervical nerve roots anatomically in cadavers and to assess its value in the clinical setting. METHODS Three positional maneuvers of the upper limb were tested on three cadavers to determine the displacement by stretch of the nerve roots C5, C6 and C7. The maneuver which was most efficient in nerve root displacement was applied in 24 patients with confirmed symptomatic cervical nerve root compression (cases) and 65 controls to assess the clinical value of the test. RESULTS The most efficient way to displace the cervical nerve roots by stretch was to apply dorsal pressure on the humeral head with the shoulder in 80° of abduction and 30° of extension, with slight elbow flexion while the head is facing the contralateral side. This maneuver produced 4-5 mm of nerve root displacement in cadavers. This test aggravated radicular symptoms in 79% of the patients with cervical nerve root compression and was negative in 98% of the controls. CONCLUSION The described abduction extension test with posterior push on the humeral head creates a fulcrum over which the brachial plexus can be displaced to create stress on cervical nerve roots. This simple test is easy to perform clinically and aggravates radicular symptoms in most of the patients with cervical nerve root compression while it is negative in nearly all of the controls.
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Conservation des globules rouges en solution additive Erythro-Sol 5 dans des poches avec ou sans plastifiant DEHP. Transfus Clin Biol 2013. [DOI: 10.1016/j.tracli.2013.03.247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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La collecte de concentrés de globules rouges d’aphérèse représente une alternative au traitement du sang total dans des délais très courts tout en assurant une qualité optimale. Transfus Clin Biol 2013. [DOI: 10.1016/j.tracli.2013.03.151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Flow Visualization of the Rubber Compounding Cycle in an Internal Mixer based on Elastomer Blends. INT POLYM PROC 2013. [DOI: 10.3139/217.890023] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
A flow visualization study of the blending of elastomers and the subsequent mixing of carbon black and oil in an internal mixer is described. The elastomers studied were natural rubber, cis-polybutadiene and a solution styrene-butadiene copolymer. Studies were made of addition to the mixer of mini bales of earch rubber pigmented with different colors and their subsequent homogenization. Subsequently we investigated the blending of bales of the different rubbers and determined the homogenication times. Similar investigations were made of the addition of carbon black and oil black homogenization times and oil absorption times were determine. These are correlated with the rheological properties of the elastomers.
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Abstract
Abstract
The flow in a pin-barrel extruder has been analyzed based on a Newtonian fluid model. A numerical simulation based on the FAN method of Tadmor and his coworkers and an analytical model were used. The calculations show that the introduction of slices into screw flights and pins make the apparatus a much poorer screw pump. It would appear that the machine is though an effective continuous (distributive) mixing device.
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Flow Visualization Parallel and Perpendicular to the Rotor Axes for Elastomers and Molten Plastics in an Internal Mixer. INT POLYM PROC 2013. [DOI: 10.3139/217.870179] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Basic studies of flow visualization for elastomers and plastics in an internal mixer are described. A modified laboratory mixer with transparent front and trasverse windows was used to observe parallel and perpendicular motions. Shearing, stretching and tearing motions were observed especially for elastomers. Various rotor designs were used. These indicate different flow fields along the rotor axes, and the interchange of materials between rotors. We describe the different flow fields observed for elastomers and plastics creasted by various rotor designs.
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Abstract
Abstract
A mathematical model is developed for simulation of flow in an internal mixer with two counter rotating non-intermeshing rotors is presented. The model presumes rotors with a screw flight which is separated into two sections. The mixing chamber is taken to be fully filled and rotor curvature neglected in analogy to screw extruder analyses. Lubrication theory is used and the fluid presumed Newtonian. The flow patterns within the mixing chamber are computed. The conditions under which rotor designs lead to global circulation patterns within the mixing chamber and good distributive mixing are considered. We also investigated the extent of fluid motion over rotor tips which should lead to dispersive mixing.
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Flow Visualization and Performance of a Non-Intermeshing Counter-Rotating Twin Screw Extruder. INT POLYM PROC 2013. [DOI: 10.3139/217.880165] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
A laboratory modular twin screw extruder with transverse and tangential apex windows for flow visualization is described. The machine is operated as a tengential twin screw extruder with right- and left-handed screw elements. Screw characteristic curves, Q-Δ p, were measured and compared for polyethylene in matched and staggered flight screw configurations with right-handed screw elements. Configurations with matched screw elements are better pumps. We have introduced left-handed screw elements into each screw configuration. This reduces the total pressure developed. Again matched screw element configurations are better pumps. Pressure profiles are measured along the length of the extruder. For right-handed screws, the pressure rises monotonically. Left-handed screw elements produce regions of decreasing pressure. Flow visualization investigations allow us to locate the position and follow the mechanism of the melting process. Using colored markers, we were able to see that in most (but not all cases) there was no inter-screw transfer of material.
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The role of external defects in chemical sensing of graphene field-effect transistors. NANO LETTERS 2013; 13:1962-8. [PMID: 23586702 DOI: 10.1021/nl304734g] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A fundamental understanding of chemical sensing mechanisms in graphene-based chemical field-effect transistors (chemFETs) is essential for the development of next generation chemical sensors. Here we explore the hidden sensing modalities responsible for tailoring the gas detection ability of pristine graphene sensors by exposing graphene chemFETs to electron donor and acceptor trace gas vapors. We uncover that the sensitivity (in terms of modulation in electrical conductivity) of pristine graphene chemFETs is not necessarily intrinsic to graphene, but rather it is facilitated by external defects in the insulating substrate, which can modulate the electronic properties of graphene. We disclose a mixing effect caused by partial overlap of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of adsorbed gas molecules to explain graphene's ability to detect adsorbed molecules. Our results open a new design space, suggesting that control of external defects in supporting substrates can lead to tunable graphene chemical sensors, which could be developed without compromising the intrinsic electrical and structural properties of graphene.
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