RESUMO
The synthesis of the accurate composition and morphological/structural design of multielement semiconductor materials is considered an effective strategy for obtaining high-performance hybrid photocatalysts. Herein, sulfur vacancy (Vs)-bearing In2S3/CuInS2 microflower heterojunctions (denoted Vs-In2S3/CuInS2) were formed in situ using In2S3 microsphere template-directed synthesis and a metal ion exchange-mediated growth strategy. Photocatalysts with flower-like microspheres can be obtained using hydrothermally synthesized In2S3 microspheres as a template, followed by Ostwald ripening growth during the metal cation exchange of Cu+ and In3+. The optimal heterostructured Vs-In2S3/CuInS2 microflowers exhibited CO and CH4 evolution rates of 80.3 and 11.8 µmol g-1 h-1, respectively, under visible-light irradiation; these values are approximately 4 and 6.8 times higher than those reported for pristine In2S3, respectively. The enhanced photocatalytic performance of the Vs-In2S3/CuInS2 catalysts could be attributed to the synergistic effects of the following factors: (i) the constructed heterojunctions accelerate charge-carrier separation; (ii) the flower-like microspheres exhibit highly uniform morphologies and compositions, which enhance electron transport and light harvesting; and (iii) the vs. may trap excited electrons and, thus, inhibit charge-carrier recombination. This study not only confirms the feasibility of the design of heterostructures on demand, but also presents a simple and efficient strategy to engineer metal sulfide photocatalysts with enhanced photocatalytic performance.
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OBJECTIVES: To research the inherent properties of the co-expression of three types degumming-related enzymes and breed more powerful degumming strains. RESULTS: Six tandem multimers of the pectate lyase gene, the xylanase gene, and the endo-1,4-ß-mannanase gene, which are essential for degumming process, were co-expressed and evaluated in Escherichia coli BL21(DE3). The xyl91 gene had a synergistic effect with endo-1,4-ß-mannanase and pectate lyase from DCE-01, when xyl gene was replaced with xyl91 in the multimer. The recombinant pET-pxm(91x) was selected and transformed into the original degumming strain DCE-01, which led to an enzymatic activity improvement. Furthermore, the weight loss, reducing sugar and COD value of the sample treated with the new engineered strain pET-pxm(91x)/DCE-01 increased to 22.5 %, 460 mg ml-1 and 4.9, respectively. CONCLUSIONS: The co-expression of degumming-related enzyme genes may be applied in industrial tests and represents a novel direction for bio-degumming research.
Assuntos
Plasmídeos/genética , Polissacarídeo-Liases/genética , Xilosidases/genética , Biodegradação Ambiental , Biotecnologia/métodos , Escherichia coli/enzimologia , Escherichia coli/metabolismo , Manosidases/genéticaRESUMO
Xylanases catalyze the hydrolysis of xylan, a major hemicellulose component of cell wall besides cellulose in most plant species. To extract cellulose fibers, it will be invaluable to screen for more effective xylanase-producing microorganisms. In this paper a new strategy for easy screening of xylanase-producing strains from the degumming line was presented. Using this strategy, a weak-acidic, cellulase-free xylanase from Bacillus subtilis has been isolated, purified and characterized. The xylanase showed high specific activity (36,633.4 U/mg), presented stable characteristics and can be separated and purified simply, with molecular weight 23.3 kD, pI 9.63. It reached its optimal activity at pH 5.8 and 60 °C, and retained over 80% of its maximal activity after pre-incubation at temperature 60 °C or pH 4.6 ~ 6.4. Also, a two-step purification procedure based on the combination of ultrafiltration and gel filtration chromatography was introduced and described, achieving 17-fold purification with 68.11% yield.
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Bacillus subtilis/enzimologia , Bacillus subtilis/isolamento & purificação , Microbiologia Ambiental , Xilosidases/isolamento & purificação , Xilosidases/metabolismo , Cromatografia em Gel , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Ponto Isoelétrico , Peso Molecular , Temperatura , Ultrafiltração/métodos , Xilosidases/químicaRESUMO
Designing efficient photocatalysts is vital for the photoreduction of CO2 to produce solar fuels, helping to alleviate issues of fossil fuel depletion and global warming. In this work, a novel ZnCr-LDH/Ti3C2Tx Schottky junction is successfully synthesized using an in situ coprecipitation method. ZnCr-LDH nanoflakes collectively grow on the surface of Ti3C2Tx MXene nanosheets. When using Ti3C2Tx MXene as a cocatalyst in the prepared heterojunction, the light absorption intensity, photo-induced electron separation and migration efficiency increase. As a result, the composite ZnCr-LDH/Ti3C2Tx results in significant improvement in the performance of photocatalytic CO2 reduction under simulated solar irradiation. The optimized sample ZCTC25 has the highest photocatalytic CO2 reduction rates of 122.45 µmol g-1 CO and 19.95 µmol g-1 CH4 (after 6 h of irradiation). These values are approximately 2.65 times higher than those of pristine ZnCr-LDH. The product selectivity towards CO is 86%. This work provides a new method for the construction of novel 2D semiconductor photocatalysts and enriches the application of an unusual type of layered double hydroxides in the photoreduction of CO2.
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Among industrial fiber crops, jute is ranked second to cotton in terms of yield and planting area worldwide. The traditional water retting and chemical semi-degumming methods restrict the development of the jute industry. Jute fiber can be extracted from jute bast through mechanical rolling (preprocessing), culture of bacteria, soaking fermentation (liquor ratio = 10, inoculum size = 1 %, temperature = 35 °C, and time = 15 h), inactivation, washing, and drying. Pectobacterium sp. DCE-01 secretes key degumming enzymes: pectinase, mannase, and xylanase, which match well the main non-cellulosic components of jute bast. Compared with the traditional water retting degumming, the bio-degumming cycle is shortened from more than 10 days to 15 h. The proposed bio-degumming achieved higher efficiency and lower pollution than water retting and chemical semi-degumming.
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ß-mannanase has shown compelling biological functions because of its regulatory roles in metabolism, inflammation, and oxidation. This study separated and purified the ß-mannanase from Bacillus subtilis BE-91, which is a powerful hemicellulose-degrading bacterium using a "two-step" method comprising ultrafiltration and gel chromatography. The purified ß-mannanase (about 28.2 kDa) showed high specific activity (79, 859.2 IU/mg). The optimum temperature and pH were 65°C and 6.0, respectively. Moreover, the enzyme was highly stable at temperatures up to 70°C and pH 4.5-7.0. The ß-mannanase activity was significantly enhanced in the presence of Mn2+, Cu2+, Zn2+, Ca2+, Mg2+, and Al3+ and strongly inhibited by Ba2+ and Pb2+. Km and Vmax values for locust bean gum were 7.14 mg/mL and 107.5 µmol/min/mL versus 1.749 mg/mL and 33.45 µmol/min/mL for Konjac glucomannan, respectively. Therefore, ß-mannanase purified by this work shows stability at high temperatures and in weakly acidic or neutral environments. Based on such data, the ß-mannanase will have potential applications as a dietary supplement in treatment of inflammatory processes.
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Bacillus subtilis/química , Inflamação/tratamento farmacológico , beta-Manosidase/isolamento & purificação , beta-Manosidase/farmacologia , Cromatografia em Gel/métodos , Suplementos Nutricionais , Concentração de Íons de Hidrogênio , Temperatura , Ultrafiltração/métodosRESUMO
A Gram-negative, non-motile, non-spore-forming bacterial strain designated IBFC2009(T) was isolated from soil of a bamboo plantation. The strain could grow at 11 degrees C approximately 39 degrees C, pH 6.0-9.0, and in the presence of 0 approximately 5% NaCl. Based on 16S rRNA gene sequence analysis, Strain IBFC2009(T) belonged to the genus Sphingobacterium and showed the highest sequence similarity of 94.6% (S. composti T5-12(T)) with the type strains within the genus. The major fatty acids were summed feature 3 (iso-C(15:0) 2-OH and/or C(16:1) omega7c, 34.4%), iso-C(15:0) (22.4%), C(16:0) 3-OH (15.2%), and iso-C(17:0) 3-OH (12.8%). The G+C content of the genomic DNA was 41.0 mol%. According to the phenotypic and genotypic characteristics, Strain IBFC2009(T) should represent a novel species of the genus Sphingobacterium, for which the name Sphingobacterium bambusae sp. nov. is proposed. The type strain is IBFC2009(T) (=CCTCC AB 209162(T) =KCTC 22814(T)).