Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.596
Filtrar
1.
Eur J Med Chem ; 184: 111749, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31589992

RESUMO

Fructose-1,6-bisphosphatase (FBPase) is an essential enzyme of GNG pathway. Significant advances demonstrate the FBPase plays a critical role in treatment of diabetes. Numerous FBPase inhibitors were developed by targeting AMP site, nevertheless, none of these inhibitors has exhibited suitable potency and druggability. Herein, a new allosteric site (C128) on FBPase was discovered, and several nitrostyrene compounds exhibiting potent FBPase inhibitions were found covalently bind to C128 site on FBPase. Mutagenesis suggest that C128 is the only cysteine that can influence FBPase inhibition, the N125-S124-S123 pathway was most likely involved in allosteric signaling transmission between C128 and active site. However, these nitrostyrenes may bind with multiple cysteine besides C128 in FBPase. To improve pocket selectivity, a series of novel compounds (14a-14n) were re-designed rationally by integrating fragment-based covalent virtual screening and machine-learning-based synthetic complexity evaluation. As expected, the mass spectrometry validated that the proportion of title compounds binding to the C128 in FBPase was significantly higher than that of nitrostyrenes. Notably, under physiological and pathological conditions, the treatment of compounds 14b, 14c, 14i or 14n led to potent inhibition of glucose production, as well as decreased triglyceride and total cholesterol levels in mouse primary hepatocytes. We highlight a novel paradigm that molecular targeting C128 site on FBPase can have potent hypoglycemic effect.


Assuntos
Descoberta de Drogas , Inibidores Enzimáticos/farmacologia , Frutose-Bifosfatase/antagonistas & inibidores , Hipoglicemiantes/farmacologia , Sítio Alostérico/efeitos dos fármacos , Animais , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Frutose-Bifosfatase/metabolismo , Glucose/antagonistas & inibidores , Glucose/biossíntese , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Hipoglicemiantes/síntese química , Hipoglicemiantes/química , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Simulação de Dinâmica Molecular , Estrutura Molecular , Ratos , Relação Estrutura-Atividade
2.
Nat Commun ; 10(1): 4049, 2019 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-31492867

RESUMO

Food production in green crops is severely limited by low activity and poor specificity of D-ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) in natural photosynthesis (NPS). This work presents a scientific solution to overcome this problem by immobilizing RuBisCO into a microfluidic reactor, which demonstrates a continuous production of glucose precursor at 13.8 µmol g-1 RuBisCO min-1 from CO2 and ribulose-1,5-bisphosphate. Experiments show that the RuBisCO immobilization significantly enhances enzyme stabilities (7.2 folds in storage stability, 6.7 folds in thermal stability), and also improves the reusability (90.4% activity retained after 5 cycles of reuse and 78.5% after 10 cycles). This work mimics the NPS pathway with scalable microreactors for continuous synthesis of glucose precursor using very small amount of RuBisCO. Although still far from industrial production, this work demonstrates artificial synthesis of basic food materials by replicating the light-independent reactions of NPS, which may hold the key to food crisis relief and future space colonization.


Assuntos
Enzimas Imobilizadas/metabolismo , Glucose/biossíntese , Microfluídica/métodos , Fotossíntese , Ribulose-Bifosfato Carboxilase/metabolismo , Dióxido de Carbono/metabolismo , Produtos Agrícolas/metabolismo , Estabilidade Enzimática , Glucose/química , Folhas de Planta/metabolismo , Reprodutibilidade dos Testes , Ribulosefosfatos/metabolismo , Temperatura
3.
Mol Genet Genomics ; 294(6): 1375-1383, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31214765

RESUMO

Forkhead box O (FoxO) is a downstream transcription factor of the insulin-signaling pathway, which plays vital roles in the growth and metabolism of organisms. In this study, BmFoxO was overexpressed in BmE cells, in which proliferation was inhibited and apoptosis was increased. The transgenic vector overexpressing BmFoxO was constructed, and the transgenic silkworm line A4FoxO was generated via embryonic microinjection. The body size of A4FoxO silkworm was smaller than that of non-transgenic silkworm (WT). The quantitative polymerase chain reaction results revealed that the insulin pathway was enhanced and the growth-related TOR pathway was suppressed. Furthermore, the translation of proteins in the fat body of A4FoxO silkworm was inhibited. The expression level of genes involved in the glucose synthesis and lipolysis pathways was increased, whereas that of genes involved in fat synthesis was decreased. Oil red O staining revealed that the amount of lipid droplets was reduced in A4FoxO silkworms compared with WT. Further analysis showed that the content of triglyceride and glycogen was significantly decreased in fat body, but the content of glucose and trehalose was increased in the hemolymph of A4FoxO silkworms. These results suggest that the enhanced expression of BmFoxO disturbs glycolipid metabolism and affects silkworm growth.


Assuntos
Bombyx/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Glucose/biossíntese , Proteínas de Insetos/metabolismo , Lipólise , Animais , Animais Geneticamente Modificados/genética , Animais Geneticamente Modificados/metabolismo , Bombyx/embriologia , Bombyx/genética , Bombyx/crescimento & desenvolvimento , Linhagem Celular , Proliferação de Células , Corpo Adiposo/metabolismo , Fatores de Transcrição Forkhead/genética , Proteínas de Insetos/genética , Larva/crescimento & desenvolvimento , Metabolismo dos Lipídeos/genética , Lipólise/genética , Açúcares/metabolismo , Triglicerídeos/metabolismo
4.
Lipids ; 54(6-7): 369-379, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31124166

RESUMO

Dysregulated hepatic gluconeogenesis is a hallmark of insulin resistance and type 2 diabetes mellitus (T2DM). Although existing drugs have been proven to improve gluconeogenesis, achieving this objective with functional food is of interest, especially using conjugated linoleic acid (CLA) found in dairy products. Both cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12) isomers of CLA were tested in human (HepG2) and rat (H4IIE) hepatocytes for their potential effects on gluconeogenesis. The hepatocytes exposed for 24 h with 20 µM of c9,t11-CLA had attenuated the gluconeogenesis in both HepG2 and H4IIE by 62.5% and 80.1%, respectively. In contrast, t10,c12-CLA had no effect. Of note, in HepG2 cells, the exposure of c9,t11-CLA decreased the transcription of gluconeogenic enzymes, cytosolic phosphoenolpyruvate carboxykinase (PCK1) by 87.7%, and glucose-6-phosphatase catalytic subunit (G6PC) by 38.0%, while t10,c12-CLA increased the expression of G6PC, suggesting the isomer-specific effects of CLA on hepatic glucose production. In HepG2, the peroxisome proliferator-activated receptor (PPAR) agonist, rosiglitazone, reduced the glucose production by 72.9%. However, co-administration of c9,t11-CLA and rosiglitazone neither exacerbated nor attenuated the efficacy of rosiglitazone to inhibit glucose production; meanwhile, t10,c12-CLA abrogated the efficacy of rosiglitazone. Paradoxically, PPARγ antagonist GW 9662 also led to 70.2% reduction of glucose production and near undetectable PCK1 expression by abrogating CLA actions. Together, while the precise mechanisms by which CLA isomers modulate hepatic gluconeogenesis directly or via PPAR warrant further investigation, our findings establish that c9,t11-CLA suppresses gluconeogenesis by decreasing PEPCK on hepatocytes.


Assuntos
Glucose/biossíntese , Hepatócitos/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/antagonistas & inibidores , Ácidos Linoleicos Conjugados/farmacologia , Fosfoenolpiruvato Carboxiquinase (GTP)/antagonistas & inibidores , Animais , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Perfilação da Expressão Gênica , Gluconeogênese/efeitos dos fármacos , Gluconeogênese/genética , Células Hep G2 , Hepatócitos/química , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Ácidos Linoleicos Conjugados/química , Fosfoenolpiruvato Carboxiquinase (GTP)/genética , Fosfoenolpiruvato Carboxiquinase (GTP)/metabolismo , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Estereoisomerismo , Relação Estrutura-Atividade
5.
Eur J Pharm Sci ; 134: 7-19, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30978382

RESUMO

This paper describes the improved integrated minimal model for healthy subjects and patients with type 2 diabetes and the work leading up to this model. The original integrated minimal model characterizes simultaneously glucose and insulin following intravenous glucose tolerance test (IVGTT) in healthy subjects and provides apart from estimates of indices for insulin sensitivity (Si) and glucose effectiveness (SG), also full simulation capabilities. However, this model was developed using IVGTT data of total glucose and consequently, the model cannot separate hepatic glucose production from glucose disposal. By fitting the original integrated minimal model to IVGTT data of labelled and total glucose, we show that all parameter estimates of the glucose sub-model were significantly different between the fits, in particular, SG, which was ~3 fold higher with total, compared to labelled glucose. In addition, the time profiles of hepatic glucose production, obtained from the model, were unphysiological in most subjects. To correct these flaws, we developed the improved integrated minimal model based on the non-integrated, two-compartment minimal model. The improved integrated minimal model showed physiologically plausible dynamic time profiles of hepatic glucose production and all parameter estimates were compatible with those reported in original publication of the non-integrated minimal model. The integrated minimal model offers the benefits of the original integrated minimal model with simulation capabilities, in presence of endogenous insulin, combined with the benefits of the non-integrated minimal model, which accurately estimates the clinical indices of insulin sensitivity and glucose effectiveness. In addition, the improved integrated minimal model describes, apart from healthy subjects, also patients with type 2 diabetes.


Assuntos
Glicemia/biossíntese , Glicemia/metabolismo , Insulina/sangue , Diabetes Mellitus Tipo 2 , Glucose/biossíntese , Glucose/metabolismo , Teste de Tolerância a Glucose , Voluntários Saudáveis , Humanos , Resistência à Insulina , Fígado , Matemática , Modelos Biológicos
6.
Biomolecules ; 9(4)2019 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-30925658

RESUMO

Developing an optimum pretreatment condition to enhance glucose recovery assessed the potential of Chloris barbata, which is a common invasive weed in Thailand, as a feedstock for bioethanol production. Chloris barbata was exposed to autoclave-assisted alkaline pretreatment by using different sodium hydroxide (NaOH) concentrations (1% to 4%) and heat intensities (110 °C to 130 °C) that were dissipated from autoclaving. The optimum condition for pretreatment was determined to be 2% NaOH at 110 °C for 60 min. At this condition, maximum hydrolysis efficiency (90.0%) and glucose recovery (30.7%), as compared to those of raw C. barbata (15.15% and 6.20%, respectively), were observed. Evaluation of glucose production from 1000 g of C. barbata based on material balance analysis revealed an estimated yield of 304 g after pretreatment at the optimum condition when compared to that of raw C. barbata (61 g), an increase of five-fold. Structural analysis by the scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed the disruption of the intact structure of C. barbata and an increase in the cellulose crystallinity index (CrI), respectively. The results from this study demonstrate the efficiency of using C. barbata as a potential feedstock for bioethanol production.


Assuntos
Glucose/biossíntese , Poaceae/efeitos dos fármacos , Hidróxido de Sódio/farmacologia , Hidrólise , Poaceae/metabolismo , Hidróxido de Sódio/química , Soluções , Tailândia
7.
Methods Mol Biol ; 1957: 365-384, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30919366

RESUMO

Type II diabetes is one of the most serious worldwide public health problems, and its hallmark is insulin resistance, obesity associated with chronic inflammation, and defective islet ß-cell function. ß-Arrestins play important roles in diabetes pathogenesis through scaffolding insulin-induced AKT activation in the liver, suppressing peroxisome proliferator-activated receptor-γ-mediated adipogenesis and inflammatory responses in adipose tissue and through promoting GLP-1-induced insulin secretion in the islet. The current chapter provides detailed protocols for both in vitro and in vivo studies of the function of ß-arrestins associated with type II diabetes.


Assuntos
Biologia Molecular/métodos , beta-Arrestinas/metabolismo , Adipócitos/metabolismo , Animais , Células da Medula Óssea/citologia , Células Cultivadas , Regulação da Expressão Gênica , Glucose/biossíntese , Hepatócitos/metabolismo , Resistência à Insulina , Secreção de Insulina , Células Secretoras de Insulina/metabolismo , Macrófagos/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transdução de Sinais , Coloração e Rotulagem
8.
Bioresour Technol ; 283: 67-75, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30901590

RESUMO

A process strategy to aid in optimal enzymatic hydrolysis through the addition of polyethylene glycol (PEG6000) was tested for separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). Pretreated wheat straw at 30% solids (w/w) loading was enzymatically hydrolyzed with 0, 0.5, 1, 1.5, 2 and 2.5% of PEG6000 through SHF and SSF. During SHF, bioethanol concentration of 107.5 g/L (2.5% PEG6000) was achieved. SSF ethanol concentration were about 113 g/L at 1.5% PEG6000 addition. A technoeconomic feasibility showed a return on investment (ROI) of 8.13% using 0.5% PEG6000 for SHF (96 h) and 12.25% ROI for SSF control (72 h). Life cycle assessment for the various scenarios indicated higher environmental gains for best cases of SSF over SHF. The study shows the SSF approach (0% PEG6000; 72 h) facilitates higher process efficiencies; technoeconomic gains and high environmental sustainability for future scale-up and commercial realization.


Assuntos
Biocombustíveis , Etanol/metabolismo , Fermentação , Glucose/biossíntese , Triticum/metabolismo , Hidrólise , Polietilenoglicóis/metabolismo
9.
Bioresour Technol ; 282: 245-253, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30870690

RESUMO

Current research aimed to increase mixotrophic biomass from various organic carbon sources by exploring best light conditions. Three substrates glucose, acetic acid and glycerol were studied for their effects on mixotrophic microalgae cultivation under four light conditions. Light irradiance exhibited variability in growth response and photosynthetic efficiency based on type of substrates used in mixotrophic growth. Each substrate showed variability in light requirements for their effective assimilations. From growth responses, glucose and acetic acid respectively exhibited heterotrophic and mixotrophic (better growth in light) natures. Continuous light-deficient condition was adequate for effective mixotrophic growth as well as energy saving for glucose. However, light-sufficient condition required for effective acetic acid supported mixotrophic growth. Mixotrophic benefits from glycerol and its uptake by Chlorella protothecoides was negligible in all light conditions. Investigation of heterotrophic biomass contribution by various substrates in overall mixotrophic yield, glucose offered maximum approx. 43% contribution.


Assuntos
Clorófitas/metabolismo , Microalgas/metabolismo , Biomassa , Chlorella/crescimento & desenvolvimento , Chlorella/metabolismo , Chlorella/efeitos da radiação , Clorófitas/crescimento & desenvolvimento , Clorófitas/efeitos da radiação , Glucose/biossíntese , Processos Heterotróficos , Microalgas/crescimento & desenvolvimento , Microalgas/efeitos da radiação , Fotossíntese
10.
Nat Commun ; 10(1): 714, 2019 02 12.
Artigo em Inglês | MEDLINE | ID: mdl-30755615

RESUMO

Glucose homeostasis is partly controlled by the energy sensor mechanistic target of rapamycin (mTOR) in the muscle and liver. However, whether mTOR in the small intestine affects glucose homeostasis in vivo remains unknown. Here, we first report that delivery of rapamycin or an adenovirus encoding the dominant negative acting mTOR-mutated protein into the upper small intestine is sufficient to inhibit small intestinal mTOR signaling and lower glucose production in rodents with high fat diet-induced insulin resistance. Second, we found that molecular activation of small intestinal mTOR blunts the glucose-lowering effect of the oral anti-diabetic agent metformin, while inhibiting small intestinal mTOR alone lowers plasma glucose levels by inhibiting glucose production in rodents with diabetes as well. Thus, these findings illustrate that inhibiting upper small intestinal mTOR is sufficient and necessary to lower glucose production and enhance glucose homeostasis, and thereby unveil a previously unappreciated glucose-lowering effect of small intestinal mTOR.


Assuntos
Glicemia/metabolismo , Glucose/biossíntese , Intestino Delgado/metabolismo , Serina-Treonina Quinases TOR/antagonistas & inibidores , Adenoviridae/genética , Animais , Dieta Hiperlipídica , Homeostase , Resistência à Insulina , Intestino Delgado/efeitos dos fármacos , Masculino , Metformina/farmacologia , Ratos , Ratos Sprague-Dawley , Transdução de Sinais , Sirolimo/farmacologia , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/metabolismo
11.
Bioresour Technol ; 280: 447-458, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30777703

RESUMO

This review analyses the relevant studies which focused on hydrogen synthesis by dark fermentation of galactose from macroalgal biomass by discussing the inoculum-related pretreatments, batch fermentation and inhibition, continuous fermentation systems, bioreactor designs for continuous operation and ionic liquid-assisted catalysis. The potential for process development is also revisited and the challenges towards suppressing glucose dominance over a galactose-based hydrogen production system are presented. The key challenges in the pretreatment process aiming to achieve a maximum recovery of upgradable (fermentable) sugars from the hydrolysates and promoting the concomitant detoxification of the hydrolysates have also been highlighted. The research avenues for bioprocess intensification connected to enhance selective sugar recovery and effective detoxification constitute the critical steps to develop future red macroalgae-derived galactose-based robust biohydrogen production system.


Assuntos
Biomassa , Fermentação , Galactose/metabolismo , Hidrogênio/metabolismo , Alga Marinha/metabolismo , Glucose/biossíntese
12.
Bioresour Technol ; 279: 124-131, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30716604

RESUMO

Corn stover pretreatment by MgO-ethanol was investigated to improve sugar recovery by reducing sugar degradation and enhance enzymatic hydrolysis by improving delignification and reducing inhibitor formation. Results showed MgO as an effective additive and Lewis base, functioned to neutralize the acids released from hemicellulose during pretreatment, reduce monosaccharide degradation and inhibitor formation, and enhance delignification. The optimal pretreatment conditions were 50% ethanol, 0.08 mol/L MgO, and 10% solid loading at 190 °C for 40 min. Under optimal conditions, 98% glucose and 92% xylose were recovered with 89% glucan and 71% xylan recoveries and 60% lignin removal. A total sugar yield of 63% on a received biomass basis after enzymatic hydrolysis was obtained with 78% glucose and 41% xylose yields. The resulting biomass slurry was near-neutral and free of furfural and 5-hydroxymethylfurfural. Thus, the process to isolate high-purity value-added lignin and recover sugars from biomass liquor can be largely simplified.


Assuntos
Zea mays/metabolismo , Biomassa , Etanol/metabolismo , Furaldeído/metabolismo , Glucose/biossíntese , Hidrólise , Lignina/metabolismo , Óxido de Magnésio/farmacologia , Polissacarídeos/metabolismo , Xilose/biossíntese
13.
Braz J Microbiol ; 50(2): 395-404, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30637642

RESUMO

The present work refers to a process involving the use of dilute nitric acid pretreatment and enzymatic hydrolysis for the transformation of rice straw into simple sugars. Acid pre-treated rice straw was separated into the pulp and supernatant through centrifugation and filtration. The two fractions are then converted into simple sugars by combined action of microbes producing cellulase and laccase enzymes. These microbes were isolated from soil samples which were collected from different locations with varying altitudes, expected to harbour microbes with high-hydrolysing activity. The nitric acid pretreatment was carried out at 30 °C, 200 rpm for 72 h. After 72 h, the culture supernatants were analysed for the presence of glucose with the help of HPLC. The supernatant fraction separated after the acid pre-treated rice straw produced highest amount of glucose (205 mg/g of rice straw) upon subsequent hydrolysis with synergistic action of cellulase and laccase-producing microbes.


Assuntos
Celulase/metabolismo , Glucose/biossíntese , Lacase/metabolismo , Lignina/metabolismo , Ácido Nítrico/farmacologia , Oryza/metabolismo , Saccharomyces cerevisiae/metabolismo , Bacillus/enzimologia , Etanol/metabolismo , Hidrólise , Índia , Micrococcaceae/enzimologia , Oryza/microbiologia
14.
Cell Commun Signal ; 17(1): 8, 2019 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-30683114

RESUMO

BACKGROUND: Ghrelin modulates many physiological processes. However, the effects of intestinal ghrelin on hepatic glucose production (HGP) are still unclear. The current study was to explore the roles of intestinal ghrelin on glucose homeostasis and insulin signaling in the liver. METHODS: The system of intraduodenal infusion and intracerebral microinfusion into the nucleus of the solitary tract (NTS) in the normal chow-diet rats and pancreatic-euglycemic clamp procedure (PEC) combined with [3-3H] glucose as a tracer were used to analyze the effect of intestinal ghrelin. Intraduodenal co-infusion of ghrelin, tetracaine and Activated Protein Kinase (AMPK) activator (AICAR), or pharmacologic and molecular inhibitor of N-methyl-D-aspartate receptors within the dorsal vagal complex, or hepatic vagotomy in rats were used to explore the possible mechanism of the effect of intestinal ghrelin on HGP. RESULTS: Our results demonstrated that gut infusion of ghrelin inhibited duodenal AMP-dependent protein kinase (AMPK) signal pathways, increased HGP and expression of gluconeogenic enzymes, and decreased insulin signaling in the liver of the rat. Intraduodenal co-infusion of ghrelin receptor antagonist [D-Lys3]-GHRP-6 and AMPK agonist with ghrelin diminished gut ghrelin-induced increase in HGP and decrease in glucose infusion rate (GIR) and hepatic insulin signaling. The effects of gut ghrelin were also negated by co-infusion with tetracaine, or MK801, an N-methyl-D-aspartate (NMDA) receptor inhibitor, and adenovirus expressing the shRNA of NR1 subunit of NMDA receptors (Ad-shNR1) within the dorsal vagal complex, and hepatic vagotomy in rats. When ghrelin and lipids were co-infused into the duodenum, the roles of gut lipids in increasing the rate of glucose infusion (GIR) and lowering HGP were reversed. CONCLUSIONS: The current study provided evidence that intestinal ghrelin has an effect on HGP and identified a neural glucoregulatory function of gut ghrelin signaling.


Assuntos
Encéfalo/metabolismo , Trato Gastrointestinal/metabolismo , Grelina/farmacologia , Glucose/biossíntese , Insulina/metabolismo , Fígado/metabolismo , Transdução de Sinais , Adenilato Quinase/antagonistas & inibidores , Adenilato Quinase/metabolismo , Animais , Duodeno/efeitos dos fármacos , Duodeno/metabolismo , Jejum , Trato Gastrointestinal/efeitos dos fármacos , Homeostase , Mucosa Intestinal/metabolismo , Fígado/efeitos dos fármacos , Fígado/enzimologia , Masculino , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacos
15.
Bioresour Technol ; 278: 82-91, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30684727

RESUMO

The main aim of this study was to optimize pretreatment strategies of Miscanthus × giganteus for biosuccinic acid production. A successful pretreatment with organosolv method (80% w/w of glycerol, 1.25% of H2SO4), prevented sugars conversion to furfurals and organic acids, and thereby resulted in high sugar recovery (glucan > 98%, xylan > 91%) and biomass delignification (60%). Pretreated biomass was subjected to hydrolysis with various cellulolytic enzyme cocktails (Viscozyme® L, Carezyme 1000L®, ß-Glucanase, Cellic® CTec2, Cellic® HTec2). The most effective enzymes mixture composed of Cellic® CTec2 (10% w/w), ß-Glucanase (5% w/w) and Cellic® HTec2 (1% w/w) resulted in high glucose (93.1%) and xylose (69.2%) yields after glycerol-based pretreatment. Succinic acid yield of 75-82% was obtained after hydrolysates fermentation, using Actinobacillus succinogenes 130Z. Finally a successful downstream concept for succinic acid purification was proposed. The succinic acid recovery with high purity (>98%) was developed.


Assuntos
Actinobacillus/metabolismo , Poaceae/metabolismo , Ácido Succínico/metabolismo , Biomassa , Fermentação , Glucose/biossíntese , Hidrólise , Especificidade por Substrato , Xilose/biossíntese
16.
Bioresour Technol ; 275: 402-409, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30605827

RESUMO

Lignocellulosic biomass is a feedstock with the potential to be converted into value-added bioproducts. The use of enzymatic hydrolysis allows the cleavage of lignocellulose into their monomeric units, but there are some drawbacks that make its use in industrial biocatalysis unfeasible. In the present study, we describe the hydrolysis of brewer's spent grain (BSG) with an enzymatic cocktail produced by Aspergillus niger CECT 2700 and its comparison with commercial enzymes. In addition, it was determined whether pretreating the BSG (non-pressurized alkaline hydrolysis or treatment with cholinium glycinate ionic liquid) is necessary. Results show that both pretreatments enhanced xylose release (10.55 ±â€¯0.07 g/L and 8.14 ±â€¯0.13 g/L respectively), meanwhile the hydrolysis of raw BSG with the enzymatic cocktail produced solutions containing high levels of glucose (18.45 ±â€¯1.66 g/L) and xylose (6.38 ±â€¯0.26 g/L).


Assuntos
Grão Comestível/metabolismo , Fermentação , Glucose/biossíntese , Xilose/biossíntese , Biocatálise , Biomassa , Hidrólise , Lignina/metabolismo
17.
J Biosci Bioeng ; 127(3): 340-344, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30237013

RESUMO

Efficient cellulosic biomass saccharification technologies are required to meet biorefinery standards. Biological simultaneous enzyme production and saccharification (BSES), which is glucose production from cellulosic biomass by Clostridium thermocellum, can be a reliable cellulose saccharification technology for biorefineries. However, the current BSES processes require purified ß-glucosidase supplementation. In this study, recombinant bacteria expressing the ß-glucosidase gene were developed and directly applied to BSES. The engineered Escherichia coli expressing the thermostable ß-glucosidase gene from Thermoanaerobacter brockii exhibited 0.5 U/ml of ß-glucosidase activities. The signal peptide sequence of lytF gene from Bacillus subtilis was the most appropriate for the ß-glucosidase secretion from Brevibacillus choshinensis, and the broth exhibited 0.74 U/ml of ß-glucosidase activities. The engineered E. coli and B. choshinensis expressing the thermostable ß-glucosidase gene produced 47.4 g/L glucose and 49.4 g/L glucose, respectively. Glucose was produced by the hydrolysis of 100 g/L Avicel cellulose for 10 days through BSES, and the product yield was similar to that obtained through BSES with purified ß-glucosidase supplementation. Our findings indicate that the direct supplementation of ß-glucosidase using bacterial cells expressing ß-glucosidase gene or their broth was applicable to BSES, suggesting the potential of this process as a cost-effective approach to cellulose saccharification.


Assuntos
Bactérias/genética , Bactérias/metabolismo , Celulose/metabolismo , DNA Recombinante/genética , Glucose/biossíntese , beta-Glucosidase/biossíntese , beta-Glucosidase/genética , Celulase/biossíntese , Celulase/metabolismo , Expressão Gênica , Hidrólise , beta-Glucosidase/metabolismo
18.
Int J Biol Macromol ; 135: 1252-1260, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-30447367

RESUMO

Current research deals with immobilization of amyloglucosidase through carrier-free approach using cross-linking strategy. Cross-linked amyloglucosidase aggregates (CLAAs) with aggregation yield of 94% were prepared in 04 h by incorporating 40% ammonium sulfate and 1.5% glutaraldehyde in enzyme solution. CLAAs were characterized by optimizing various conditions including reaction time, pH, temperature and substrate concentration. It was noticed that after cross-linking no change in optimum reaction time and substrate concentration was observed however, a 5-degree shift in optimum temperature from 60 °C to 65 °C was obtained as compared to soluble amyloglucosidase. Activation energy (Ea) of amyloglucosidase as calculated from Arrhenius plot was 5.5 kcal mol-1 and 5.2 kcal mol-1 for soluble and cross-linked aggregates, respectively. Stability studies revealed that CLAAs can be used at higher temperatures for longer time period than soluble amyloglucosidase. Furthermore, data of recycling studies showed that CLAAs can be efficiently reused for 20 cycles with the retention of 63% of its initial activity. Due to the continuous reusability of CLAAs, the product formation is also increased 8 times from 5.71 mg ml-1 (soluble enzyme) to 46.548 mg ml-1 (CLAAs). Findings of this research show that carrier-free strategy is more effective for continuous hydrolysis of starch and production of glucose.


Assuntos
Aspergillus fumigatus/enzimologia , Glucana 1,4-alfa-Glucosidase/química , Glucose/biossíntese , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Amido/química , Amido/ultraestrutura , Temperatura
19.
Bioresour Technol ; 274: 281-286, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30529333

RESUMO

In this study, ball milling and ionic liquid pretreatments were utilized to alter cellulose structure prior to fast pyrolysis and enzymatic hydrolysis. The variations in the products distribution of cellulose fast pyrolysis, and their dependence on the structure of cellulose, and the temperature of fast pyrolysis were illustrated. Fast pyrolysis of pretreated cellulose yielded more levoglucosan than crystalline cellulose (14.7%) at 300 °C. Nevertheless, the levoglucosan achieved higher yield (64.3%) from crystalline cellulose at 400 °C. At last, a comparison between fast pyrolysis and enzymatic hydrolysis for cellulose saccharifaction was made. Fast pyrolysis was a promising alternative to liberate levoglucosan from cellulose. Further investigation and development were required to maximize the levoglucosan production.


Assuntos
Celulose/metabolismo , Glucose/análogos & derivados , Biomassa , Fermentação , Glucose/biossíntese , Hidrólise , Pirólise , Temperatura , Fatores de Tempo
20.
Curr Diabetes Rev ; 15(4): 328-339, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30306875

RESUMO

BACKGROUND: Both insulin deficiency and insulin resistance due to glucagon secretion cause fasting and postprandial hyperglycemia in patients with diabetes. INTRODUCTION: Metformin enhances insulin sensitivity, being used to prevent and treat diabetes, although its mechanism of action remains elusive. RESULTS: Patients with diabetes fail to store glucose as hepatic glycogen via the direct pathway (glycogen synthesis from dietary glucose during the post-prandial period) and via the indirect pathway (glycogen synthesis from "de novo" synthesized glucose) owing to insulin deficiency and glucagoninduced insulin resistance. Depletion of the hepatic glycogen deposit activates gluconeogenesis to replenish the storage via the indirect pathway. Unlike healthy subjects, patients with diabetes experience glycogen cycling due to enhanced gluconeogenesis and failure to store glucose as glycogen. These defects raise hepatic glucose output causing both fasting and post-prandial hyperglycemia. Metformin reduces post-prandial plasma glucose, suggesting that the drug facilitates glucose storage as hepatic glycogen after meals. Replenishment of glycogen store attenuates the accelerated rate of gluconeogenesis and reduces both glycogen cycling and hepatic glucose output. Metformin also reduces fasting hyperglycemia due to declining hepatic glucose production. In addition, metformin reduces plasma insulin concentration in subjects with impaired glucose tolerance and diabetes and decreases the amount of insulin required for metabolic control in patients with diabetes, reflecting improvement of insulin activity. Accordingly, metformin preserves ß-cell function in patients with type 2 diabetes. CONCLUSION: Several mechanisms have been proposed to explain the metabolic effects of metformin, but evidence is not conclusive and the molecular basis of metformin action remains unknown.


Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Glucose/antagonistas & inibidores , Hipoglicemiantes/uso terapêutico , Metformina/uso terapêutico , Gluconeogênese , Glucose/biossíntese , Glicogênio/metabolismo , Humanos , Resistência à Insulina , Fígado/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA