Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 66.648
Filtrar
1.
J Agric Food Chem ; 67(38): 10791-10799, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31497956

RESUMO

Very weak signals of fragment ions of nosiheptide could be observed using liquid chromatography-tandem mass spectrometry. The preparation of 4-hydroxymethyl-3-methyl-1H-indole-2-carboxylic acid (HMIA), a specific fragment of nosiheptide, by alkaline hydrolysis is described. HMIA showed a good mass spectrometric signal in negative electrospray ionization mode. In the new method, the nosiheptide residue in muscle tissue was hydrolyzed with sodium hydroxide aqueous solution; this was followed by cleanup using mixed mode cartridges. Identification and quantification of nosiheptide were carried out by analyzing HMIA in hydrolysate of muscles. Nosiheptide showed a good linear relationship (r > 0.996) in the calibration range of 2-500 µg/kg, and a low limit of quantification of 2 µg/kg was obtained in swine, chicken, and fish muscles. Recoveries of nosiheptide from spiked muscle samples were 85-108% with relative standard deviations less than 10%. The proposed method was successfully applied for the detection of the nosiheptide residue in medicated animal tissues samples.


Assuntos
Antibacterianos/química , Cromatografia Líquida de Alta Pressão/métodos , Resíduos de Drogas/química , Contaminação de Alimentos/análise , Carne/análise , Espectrometria de Massas em Tandem/métodos , Álcalis/química , Animais , Galinhas , Peixes , Hidrólise , Limite de Detecção , Músculos/química , Suínos , Tiazóis/química
2.
J Agric Food Chem ; 67(38): 10744-10755, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31525900

RESUMO

We previously reported that ß-glucosidase BGL1 at low concentration (15 µg mL-1) from Coprinopsis cinerea exhibited hydrolytic activity only toward laminarioligosaccharides but not toward cellooligosaccharides and gentiobiose. This study shows that BGL1 at high concentration (200 µg mL-1) also hydrolyzed cellobiose and gentiobiose, which accounted for only 0.83 and 2.05% of its activity toward laminaribiose, respectively. Interestingly, BGL1 at low concentration (1.5 µg mL-1) showed transglycosylation but BGL1 at high concentration (200 µg mL-1) did not. BGL1 utilizes only laminarioligosaccharides but not glucose, gentiobiose, and cellobiose to synthesize the higher oligosaccharides. BGL1 transferred one glucosyl residue from substrate laminarioligosaccharide to another laminarioligosaccharide as an acceptor in a ß(1 → 3) or ß(1 → 6) fashion to produce higher laminarioligosaccharides or 3-O-ß-d-gentiobiosyl-d-laminarioligosaccharides. The BGL1-digested laminaritriose exhibited approximately 90% enhancement in the anti-oxidant activity compared to that of untreated laminaritriose, implying a potential application of BGL1-based transglycosylation for the production of high value-added rare oligosaccharides.


Assuntos
Agaricales/enzimologia , Dissacarídeos/metabolismo , Proteínas Fúngicas/química , Oligossacarídeos/metabolismo , beta-Glucosidase/química , Agaricales/química , Agaricales/genética , Sequência de Aminoácidos , Dissacarídeos/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Glicosilação , Hidrólise , Cinética , Estrutura Molecular , Oligossacarídeos/química , Especificidade por Substrato , beta-Glucosidase/genética , beta-Glucosidase/metabolismo
3.
Microb Cell Fact ; 18(1): 159, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31542050

RESUMO

BACKGROUND: Xylanases randomly cleave the internal ß-1,4-glycosidic bonds in the xylan backbone and are grouped into different families in the carbohydrate-active enzyme (CAZy) database. Although multiple xylanases are detected in single strains of many filamentous fungi, no study has been reported on the composition, synergistic effect, and mode of action in a complete set of xylanases secreted by the same microorganism. RESULTS: All three xylanases secreted by Penicillium chrysogenum P33 were expressed and characterized. The enzymes Xyl1 and Xyl3 belong to the GH10 family and Xyl3 contains a CBM1 domain at its C-terminal, whereas Xyl2 belongs to the GH11 family. The optimal temperature/pH values were 35 °C/6.0, 50 °C/5.0 and 55 °C/6.0 for Xyl1, Xyl2, and Xyl3, respectively. The three xylanases exhibited synergistic effects, with the maximum synergy observed between Xyl3 and Xyl2, which are from different families. The synergy between xylanases could also improve the hydrolysis of cellulase (C), with the maximum amount of reducing sugars (5.68 mg/mL) observed using the combination of C + Xyl2 + Xyl3. Although the enzymatic activity of Xyl1 toward xylan was low, it was shown to be capable of hydrolyzing xylooligosaccharides into xylose. Xyl2 was shown to hydrolyze xylan to long-chain xylooligosaccharides, whereas Xyl3 hydrolyzed xylan to xylooligosaccharides with a lower degree of polymerization. CONCLUSIONS: Synergistic effect exists among different xylanases, and it was higher between xylanases from different families. The cooperation of hydrolysis modes comprised the primary mechanism for the observed synergy between different xylanases. This study demonstrated, for the first time, that the hydrolysates of GH11 xylanases can be further hydrolyzed by GH10 xylanases, but not vice versa.


Assuntos
Endo-1,4-beta-Xilanases/metabolismo , Proteínas Fúngicas/metabolismo , Penicillium chrysogenum/enzimologia , Polissacarídeos/metabolismo , Biocatálise , Endo-1,4-beta-Xilanases/química , Endo-1,4-beta-Xilanases/genética , Estabilidade Enzimática , Proteínas Fúngicas/química , Proteínas Fúngicas/genética , Glucuronatos/metabolismo , Temperatura Alta , Hidrólise , Família Multigênica , Oligossacarídeos/metabolismo , Penicillium chrysogenum/química , Penicillium chrysogenum/genética , Domínios Proteicos , Xilanos/metabolismo
4.
Bioresour Technol ; 293: 122055, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31472409

RESUMO

In this work, amphiphilic surfactant was obtained using dehydroabietic acid from pine rosin and then pre-adsorbed with acid-pretreated bamboo residues (AP-BR) to block the residual lignin adsorption site, which is expected to improve its enzymatic digestibility. Results from cryogenic-transmission electron microscopy (Cryo-TEM) indicated amphiphilic surfactant with PEG with polymerization degree of 34 (D-34) aggregated to form worm-like micelles, which improved enzymatic hydrolysis yield of AP-BR from 24.3% to 71.9% by pre-adsorbing with 0.8 g/L. Amphiphilic surfactants pre-adsorbed on AP-BR could reduce hydrophobicity of AP-BR, adsorption affinity and adsorption capacity of lignin for cellulase from 0.51 L/g to 0.48-0.32 L/g, from 2.9 mL/mg to 1.8-1.4 mL/mg, and from 122.3 mg/g to 101.9-21.4 mg/g, respectively. These changed properties showed compelling positive contributions (R2 > 0.9) for free enzymes in the supernatants and sequently for final enzymatic hydrolysis yield, which was caused by blocking non-productively hydrophobic adsorption between lignin and cellulase.


Assuntos
Celulase , Adsorção , Diterpenos de Abietano , Hidrólise , Lignina , Tensoativos
5.
Bioresour Technol ; 293: 122016, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31473375

RESUMO

Pretreatment is a key step in the energy utilization of lignocellulosic biomass. Different types of pretreatments (ultrafine grinding pretreatment, alkaline hydroxide peroxide pretreatment, dilute acid pretreatment, and ammonia fiber expansion pretreatment) were conducted on corn stover. The lignocellulosic composition, microstructural parameters, and glucose yield of differently pretreated corn stover were characterized and compared. Then qualitative and quantitative correlation analyses of the parameters were carried out to explore the correlations among the composition, microstructure properties, and enzymatic hydrolysis efficacy of corn stover after different types of pretreatments and identify the main properties affecting enzymatic hydrolysis. Qualitative correlation analysis found that cellulose content, specific surface area, pore volume, enzyme-accessible pore volume, and surface area of cellulose had significant positive correlations with glucose yield. The results of quantitative correlation analysis were GY = 15.01 × cellulose content-339.05, GY = 13.06 × SSA + 172.35, GY = 7226.27 × PV + 129.14, GY = 8628.61 × EAPV + 125.61, and GY = 1.18 × SAC-287.21.


Assuntos
Celulose , Zea mays , Biomassa , Carboidratos , Hidrólise
6.
Bioresour Technol ; 293: 121929, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31476565

RESUMO

In the present study, was investigated an environmentally friendly method for pretreating lignocellulosic rice straw (RS) by using 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as an ionic liquid (IL) and 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO4) as an acidic-IL (Acidic-IL) under microwave irradiation (microwave-[Bmim]Cl and microwave-[Bmim]HSO4). The conversion of lignocellulosic biomass into simple sugars requires both efficient pretreatment and hydrolysis enzymes to produce biofuels and specialty chemicals. Therefore, the applied [Bmim]Cl, [Bmim]HSO4, microwave-[Bmim]Cl, and microwave-[Bmim]HSO4 to improve hydrolysis yields. Structural analyses of the pretreated solids were performed to understand the synergistic effects of [Bmim]Cl, and [Bmim]HSO4 pretreatment under microwave irradiation (microwave-[Bmim]Cl and microwave-[Bmim]HSO4) on the efficiencies of enzymatic hydrolyses. The results of a chemical composition analysis of untreated and all pretreated RS samples by using the difference pretreatment methods showed that significant lignin removal was achieved using microwave-[Bmim]Cl (57.02 ±â€¯1.24%), followed by [Bmim]Cl only (41.01 ±â€¯2.67%), microwave-[Bmim]HSO4 (20.77 ±â€¯1.79%), and [Bmim]HSO4-only (16.88 ±â€¯1.14%). The highest glucan yield and xylan conversion achieved through the enzymatic saccharification of microwave-[Bmim]Cl-regenerated cellulose was consistent with the observations obtained from a structural analysis, which indicated a more disrupted, amorphous structure, with lowered crystallinity index (CrI) and lateral order index (LOI) of cellulose polymers. Thus results demonstrated that the pretreatment of lignocellulosic biomass with [Bmim]Cl under microwave irradiation has potential as an alternative method for pretreating lignocellulosic materials.


Assuntos
Líquidos Iônicos , Oryza , Biomassa , Hidrólise , Lignina , Micro-Ondas
7.
Bioresour Technol ; 293: 122036, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31479857

RESUMO

To improve the neutral DES (choline chloride/glycerol) pretreatment performance, three environmentally friendly heteropoly acids (phosphotungstic, phosphomolybdic and silicotungstic acids) were used as catalysts. Pretreatment with silicotungstic acid at 120 °C for 3 h resulted in 97.3% of enzymatic digestibility at an enzyme loading of 15FPU/g substrate, which was approximately eight times more than that of raw samples. More importantly, 80% of glucose yield was obtained within 12 h. Simultaneously, 81.8% of ethanol yield was achieved in the SSSF process. The efficient conversion was ascribed to the significant delignification (89.5%), which resulted in the exposure of more accessible specific surface area. This was attributed to that the proton (H+) from heteropoly acids could significantly contribute to the lignin degradation. Intriguingly, trace acetic acid (0.39 g/L) and HMF (0.21-0.95 g/L) in the pretreatment liquor were produced without any significant deleterious effects. These discoveries provide new insights for efficient biomass conversion under mild conditions.


Assuntos
Etanol , Lignina , Biomassa , Fermentação , Hidrólise , Solventes
8.
Bioresour Technol ; 293: 122074, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31491652

RESUMO

Effect of pH on waste activated sludge (WAS) hydrolysis and decomposition treating with lysozyme and rhamnolipid combined (Ly + RL) was investigated in this study. Results showed that Ly + RL system could significantly improve the release of soluble organic matters at the optimal RL dosage of 0.3 g/gSS and lysozyme dosage of 0.15 g/gSS. Alkali conditions showed better effect than that of acid on the release of soluble organics, improvement of WAS biodegradability and reduction of big floc size within Ly + RL treatment system and the optimal pH was 10. And 9591.6 mg/L soluble chemical oxygen demand (SCOD), 1612.0 mg/L protein and 1211.6 mg/L polysaccharide were released at pH10 after 12 h co-digestion. 83.7% bacteria and 92.2% archaea were decomposed at pH10. Class Gammaproteobacteria (82.4%) was the predominant bacteria after treated by Ly + RL system, and the treated WAS was beneficial for the subsequent organics bio-degradation and volatile fatty acids accumulation.


Assuntos
Muramidase , Esgotos , Glicolipídeos , Concentração de Íons de Hidrogênio , Hidrólise , Eliminação de Resíduos Líquidos
9.
Bioresour Technol ; 292: 122077, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31477347

RESUMO

In this work, alkaline hydrogen peroxide (AHP) solution with 1 wt% H2O2 was electrogenerated by oxygen reduction with a current efficiency of 75.2% in a home-made gas diffusion electrode-based electrochemical cell and used for rice straw pretreatment (0.1 g H2O2/g rice straw, 10% (w/v) biomass loading, 55 °C, 2 h). Results showed that the AHP pretreatment removed 97.56% of the initial lignin, 85.75% of the initial hemicellulose, and only 0.56% of the initial cellulose, and the specific surface area and porosity of the AHP pretreated rice straw (AHP-RS) were greatly increased. Saccharification results showed that after 48 h of enzymatic hydrolysis AHP-RS achieved a 3.2-fold increase in reducing sugar concentration compared to the untreated rice straw (5.81 and 1.81 g L-1), highlighting the potential use of this AHP solution for lignocellulose pretreatment.


Assuntos
Celulase , Oryza , Celulose , Peróxido de Hidrogênio , Hidrólise , Lignina
10.
Bioresour Technol ; 292: 122058, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31488335

RESUMO

Anaerobic digestion (AD) and pyrolysis are two promising technologies used worldwide for waste biomass treatment. Interests on intensification techniques of AD has been increasing to obtain sufficient and sustainable methane production with stable digester performance. For instance, considerable attention has been devoted to the coupling of AD with biochar, which is produced by biomass thermochemical conversion. This manuscript presents a comprehensive review about recent achievements in enhancing AD efficiency with the utilization of biochar. The key roles of biochar include enhancing and equilibrating hydrolysis, acidogenesis-acetogenesis, and methanogenesis, as well as alleviating inhibitor stress were summarized. Biochar can promote biomethane process mainly by serving as a provision for bioelectrical connections between fermentative bacteria and methanogens, a support for microbial colonies, and a reinforcer for buffer capacity. Through an overview of the early applications, this paper aims to pinpoint the potential mechanism and future explorative directions of biochar enhancing AD performance.


Assuntos
Carvão Vegetal , Metano , Anaerobiose , Biomassa , Hidrólise
11.
Chem Biol Interact ; 311: 108796, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31421116

RESUMO

Lambda-cyhalothrin (LCT) is a broad-spectrum pesticide widely used in agriculture throughout the world. This pesticide is considered a potential contaminant of surface and underground water as well as food, posing a risk to ecosystems and humans. In this sense, we decided to evaluate the activity of enzymes belonging to the purinergic system, which is linked with regulation of extracellular nucleotides and nucleosides, such as adenosine triphosphate (ATP) and adenosine (Ado) molecules involved in the regulation of inflammatory response. However, there are no data concerning the effects of LCT exposure on the purinergic system, where extracellular nucleotides act as signaling molecules. The aim of this study was to evaluate nucleotide hydrolysis by E-NTPDase (ecto-nucleoside triphosphate diphosphohydrolase), Ecto-NPP (ecto-nucleotide pyrophosphatase/phosphodiesterase), ecto-5'-nucleotidase and ecto-adenosine deaminase (E-ADA) in platelets and liver of adult rats on days 7, 30, 45 and 60 after daily gavage with 6.2 and 31.1 mg/kg bw of LCT. Gene expression patterns of NTPDases1-3 and 5'-nucleotidase were also determined in those tissues. In parallel, lambda-cyhalothrin metabolites [3-(2-chloro-3,3,3- trifluoroprop-1-enyl)-2,2-dimethyl-cyclopropane carboxylic acid (CFMP), 4-hydroxyphenoxybenzoic acid (4-OH-3-PBA), and 3-phenoxybenzoic acid (3-PBA)] were measured in plasma. Results showed that exposure rats to LCT caused a significant increase in the assessed enzymes activities. Gene expression pattern of ectonucleotidases further revealed a significant increase in E-NTPDase1, E-NTPDase2, and E-NTPDase3 mRNA levels after LCT administration at all times. A dose-dependent increase in LCT metabolite levels was also observed but there no significant variations in levels from weeks to week, suggesting steady-steady equilibrium. Correlation analyses revealed that LCT metabolites in the liver and plasma were positively correlated with the adenine nucleotides hydrolyzing enzyme, E-ADA and E-NPP activities in platelets and liver of rats exposed to lambda-cyhalothin. Our results show that LCT and its metabolites may affect purinergic enzymatic cascade and cause alterations in energy metabolism.


Assuntos
Plaquetas/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Fígado/efeitos dos fármacos , Nitrilos/farmacologia , Nucleotidases/genética , Nucleosídeos de Purina/metabolismo , Piretrinas/farmacologia , Adenosina Desaminase/genética , Adenosina Desaminase/metabolismo , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Animais , Plaquetas/enzimologia , Plaquetas/metabolismo , Cromatografia Líquida de Alta Pressão , Hidrólise , Fígado/enzimologia , Fígado/metabolismo , Masculino , Espectrometria de Massas , Nitrilos/sangue , Nitrilos/metabolismo , Nucleotidases/metabolismo , Piretrinas/sangue , Piretrinas/metabolismo , Pirofosfatases/genética , Pirofosfatases/metabolismo , Ratos , Ratos Wistar
12.
Bioresour Technol ; 291: 121839, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376673

RESUMO

Inorganic salt treatment is a novel, high-yield, and environmentally friendly approach for the production of xylo-oligosaccharides from Sugarcane bagasse with degree of polymerization of 2-5. A xylo-oligosaccharides yield of 53.79% was obtained with 0.1 M MgCl2 treatment at 180 °C/10 min, and 41.89% with 0.1 M FeCl2 treatment at 140 °C/30 min. The xylo-oligosaccharides yield from the co-catalysis of 0.05 M FeCl2 + 0.05 M MgCl2 reached 54.68% (29.34% xylobiose and 20.94% xylotriose) at 140 °C/30 min. The co-catalysis not only effectively improved the xylobiose and xylotriose contents but also increased the total yield of xylo-oligosaccharides under mild reaction conditions. Additionally, the glucose yield observed from the solid residue after inorganic salt treatment was 71.62% by enzymatic hydrolysis. Mg2+ and Fe2+ are essential for good human health without separation from the system, therefore, the inorganic salt treatment can be potentially applied in the co-production of xylo-oligosaccharides and glucose.


Assuntos
Celulose/química , Compostos Ferrosos/química , Cloreto de Magnésio/química , Oligossacarídeos/química , Saccharum/química , Catálise , Glucose/química , Hidrólise , Polimerização
13.
Bioresour Technol ; 291: 121844, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31400704

RESUMO

A low-temperature sodium hydroxide (NaOH) pretreatment for sugarcane bagasse (SCB) was obtained via the surface response design in this study. However, a large quantity of water consumption and wastewater generation which have been the common problems for alkaline pretreatment of lignocellulose still exists in this pretreatment. In order to reduce water consumption and wastewater generation, this study attempted to perform enzymatic hydrolysis and fermentation of NaOH-treated SCB without washing process. It showed that after pretreatment and solid-liquid separation, NaOH-treated SCB could be directly hydrolysed by cellulase via pH and solid-liquid adjustment without washing steps, and the maximum enzymatic hydrolysis efficiency could reach to 70.2%. A domesticated Saccharomyces cerevisiae Y2034 which can endure 6-times diluted BL was obtained, and realized 67.5% ethanol yield from the enzymatic hydrolysate of unwashed NaOH-treated SCB. It provided a clue for converting NaOH-treated lignocellulose to ethanol at low water consumption and wastewater generation.


Assuntos
Celulose/química , Etanol/química , Saccharum/química , Hidróxido de Sódio/química , Celulose/metabolismo , Temperatura Baixa , Etanol/metabolismo , Fermentação , Hidrólise , Lignina/química , Lignina/metabolismo , Saccharomyces cerevisiae/metabolismo , Saccharum/metabolismo , Águas Residuárias/química
14.
J Agric Food Chem ; 67(38): 10604-10613, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31466448

RESUMO

The aim of this study was to investigate the dipeptidyl peptidase-IV (DPP-IV) inhibition and metabolic stability of a casein-derived peptide Val-Pro-Tyr-Pro-Gln (VPYPQ) and its fragments as well as their release from casein following hydrolysis. Results showed that VPYPQ was the most potent DPP-IV inhibitory peptide among them with an IC50 value of 41.45 µM. This might be due to its two internal Pro residues at positions 2 and 4. Moreover, VPYPQ was resistant to hydrolysis by gastrointestinal enzymes and was relatively more stable to hydrolysis by DPP-IV and peptidases in plasma compared with its fragments. Additionally, oral administration of VPYPQ at a dose of 90 µmol/kg body weight could reduce the postprandial blood glucose levels in mice. More importantly, VPYPQ could be released efficiently from casein following hydrolysis by a combination of papain and in vitro digestion, reaching up to 3211.15 µg/g. Therefore, VPYPQ was a promising casein-derived DPP-IV inhibitor.


Assuntos
Caseínas/química , Preparações de Ação Retardada/química , Inibidores da Dipeptidil Peptidase IV/química , Peptídeos/química , Animais , Biocatálise , Glicemia/metabolismo , Preparações de Ação Retardada/administração & dosagem , Diabetes Mellitus/tratamento farmacológico , Diabetes Mellitus/metabolismo , Dipeptidil Peptidase 4/química , Dipeptidil Peptidase 4/metabolismo , Inibidores da Dipeptidil Peptidase IV/administração & dosagem , Teste de Tolerância a Glucose , Humanos , Hidrólise , Camundongos , Peptídeo Hidrolases/química , Peptídeo Hidrolases/metabolismo , Peptídeos/administração & dosagem , Ratos , Ratos Sprague-Dawley
15.
J Phys Chem A ; 123(36): 7710-7719, 2019 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-31433182

RESUMO

Maleamate amidohydrolase (NicF) is a key enzyme in vitamin B3 metabolism that catalyzes the hydrolysis of maleamate to produce maleic acid and ammonia. Unlike most members from the amidohydrolase superfamily it does not require a metal ion. Here, we use multiscale computational enzymology to investigate the catalytic mechanism, substrate binding, oxyanion hole, and roles of key active site residues of NicF from Bordetella bronchiseptica. In particular, molecular dynamics (MD) simulations, quantum mechanics/molecular mechanics (QM/MM) and QTAIM methods have been applied. The mechanism of the NicF-catalyzed reaction proceeds by a nucleophilic addition-elimination sequence involving the formation of a thioester enzyme intermediate (IC2 in stage 1) followed by hydrolysis of the thioester bond to form the products (stage 2). Consequently, the formation of IC2 in stage 1 is the rate-limiting step with a barrier of 88.8 kJ·mol-1 relative to the reactant complex, RC. Comparisons with related metal-dependent enzymes, particularly the zinc-dependent nicotinamidase from Streptococcus pneumonia (SpNic), have also been made to further illustrate unique features of the present mechanism. Along with -NH- donor groups of the oxyanion hole (i.e., HN-Thr146, HN-Cys150), the active site ß-hydroxyl of threonine (HO-ßThr146) is concluded to play a role in stabilizing the carbonyl oxygen of maleamate during the mechanism.


Assuntos
Amidoidrolases/química , Amidoidrolases/metabolismo , Biocatálise , Maleatos/metabolismo , Simulação de Dinâmica Molecular , Teoria Quântica , Bordetella bronchiseptica/enzimologia , Hidrólise , Maleatos/química , Estrutura Molecular
16.
Bioresour Technol ; 293: 122035, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31454731

RESUMO

This work studied the association between biomass types and MgO pretreatment using representative agricultural residues (corn stover, sorghum stalk, and wheat straw), energy crops (miscanthus, switchgrass, and big bluestem), and woody biomass (poplar). Differences in biomass chemical components (24.7-40.3% cellulose, 17.4-27.6% hemicellulose, 12.1-22.0% lignin, and 5.1-38.3% extractives) and the amount of acetic acid (1.9-5.3%) affected biomass structure and pretreatment severity. Optimal pretreatment temperature and time were 170 °C and 40 min for wheat straw and switchgrass; 180 °C and 30 min for miscanthus and poplar; and 180 °C and 40 min for corn stover, sorghum stalk, and big bluestem. Big bluestem and poplar have a larger amount of acetic acid and required more MgO loading (0.12 mol/L). Except for sorghum stalk (0.10 mol/L), the rest required less MgO loading (0.08 mol/L). Approximate MgO loading completely neutralized released acetic acid during pretreatment, reducing sugar degradation and eliminating inhibitor formation.


Assuntos
Lignina , Óxido de Magnésio , Biomassa , Hidrólise , Zea mays
17.
Bioresour Technol ; 293: 122015, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31454737

RESUMO

Lignocellulose biomass can be transformed into sustainable chemicals, materials and energy but its natural recalcitrance requires the use of pretreatment to enhance subsequent catalytic steps. Dilute acid pretreatment is one of the most common and efficient ones, however its impact has not yet been investigated simultaneously at nano- and cellular-scales. Poplar samples have been pretreated by dilute acid at different controlled severities, then characterized by combined structural and spectral techniques (scanning electron microscopy, confocal microscopy, autofluorescence, fluorescence lifetime, Raman). Results show that pretreatment favours lignin depolymerization until severity of 2.4-2.5 while at severity of 2.7 lignin seems to repolymerize as revealed by broadening of autofluorescence spectrum and strong decrease in fluorescence lifetime. Importantly, both nano-scale and cellular-scale markers can predict hydrolysis yield of pretreated samples, highlighting some connections in the multiscale recalcitrance of lignocellulose.


Assuntos
Lignina , Populus , Ácidos , Biomassa , Hidrólise , Microscopia Eletrônica de Varredura
18.
Bioresour Technol ; 291: 121813, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376669

RESUMO

The aim of this study is to evaluate the effect of leachate recirculation at a ratio of 0%, 25%, 50% or 75% of collected leachate from the Leach Bed Reactor (LBR) on food waste digestion efficiency and its subsequent methane production in the second phase of a two-phase anaerobic system. Higher hydrolysis-acidogenesis efficiency and lower energy loss were achieved in LBR with higher leachate recirculation ratio. Better biochemical balance between metabolic products and microorganisms in leachate was revealed under 50% leachate recirculation ratio, which leads to the highest hydrogen production yield in LBR resulting the highest methane production yield in the corresponding methanogenic phase which was at least 15% higher than that in other conditions. This provides an easy approach to enhance the hydrolysis efficiency and in the same time a biochemical balanced leachate to enhance methanogenic reaction of a two-phase anaerobic digestion.


Assuntos
Reatores Biológicos , Eliminação de Resíduos , Anaerobiose , Alimentos , Hidrólise , Metano
19.
Bioresour Technol ; 291: 121931, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31382093

RESUMO

This work deals with the development of an improved process for xylitol production from corn cob hydrolysate by biotechnological routes emphasizing the detoxification of corncob acid hydrolysate. The acid hydrolysate obtained by acid hydrolysis of corn cob was concentrated and detoxified by activated charcoal, membrane process and ion exchange resin process. The resultant partially purified corncob hydrolysate was used in fermentation. The fermentation of acid hydrolysate containing 56.5 g/L xylose was carried out in a 14 L fermenter at pH 4.5 for 48 h with 150 rpm stirring rate at 30 °C. A xylitol yield of 62% was achieved from the partially purified acid hydrolysate medium during fermentation using Candida tropicalis MTCC 6192. The purity of xylitol was increased to 92-94% upon downstream processing of carbonation, subsequently ion exchange process and activated charcoal.


Assuntos
Xilitol , Zea mays , Candida tropicalis , Fermentação , Hidrólise , Xilose
20.
Bioresour Technol ; 292: 121915, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31386943

RESUMO

This work studied preparation of rice husk-based solid acid and its application for efficient hydrolysis and saccharification of corncob. Rice husk-based solid acid (RH-SO3H) was prepared by one-step carbonization and sulfonation method. Analysis demonstrated that RH-SO3H exhibited aromatic carbon sheets structure bearing -SO3H, -COOH and -OH groups. The RH-SO3H was then used to hydrolyse and saccharify corncob. Compared with solid acids made from activated carbon and microcrystalline cellulose, the RH-SO3H showed the highest catalytic efficiency with the maximum reducing sugar yield of 486.53 mg/g and xylose of 253.03 mg/g, which was twice and five times higher than that of control, respectively. Its high efficiency was attributed to -OH and -COOH groups functioned synergistically with -SO3H to hydrolyse lignocellulose by adsorbing ß-1,4-glucan in corncob. This study provides a green and effective utilization technology of lignocellulosic biomass.


Assuntos
Oryza , Ácidos , Hidrólise , Xilose , Zea mays
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA