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1.
Enzyme Microb Technol ; 150: 109893, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34489046

RESUMO

In this study, a GH26 endo-mannanase (Man26A) from an Aspergillus niger ATCC 10864 strain, with a molecular mass of 47.8 kDa, was cloned in a yBBH1 vector and expressed in Saccharomyces cerevisiae Y294 strain cells. Upon fractionation by ultra-filtration, the substrate specificity and substrate degradation pattern of the endo-mannanase (Man26A) were investigated using ivory nut linear mannan and two galactomannan substrates with varying amounts of galactosyl substitutions, guar gum and locust bean gum. Man26A exhibited substrate specificity in the order: locust bean gum ≥ ivory nut mannan > guar gum; however, the enzyme generated more manno-oligosaccharides (MOS) from the galactomannans than from linear mannan during extended periods of mannan hydrolysis. MOS with a DP of 2-4 were the major products from mannan substrate hydrolysis, while guar gum also generated higher DP length MOS. All the Man26A generated MOS significantly improved the growth (approximately 3-fold) of the probiotic bacterial strains Streptococcus thermophilus and Bacillus subtilis in M9 minimal medium. Ivory nut mannan and locust bean gum derived MOS did not influence the auto-aggregation ability of the bacteria, while the guar gum derived MOS led to a 50 % reduction in bacterial auto-aggregation. On the other hand, all the MOS significantly improved bacterial biofilm formation (approximately 3-fold). This study suggests that the prebiotic characteristics exhibited by MOS may be dependent on their primary structure, i.e. galactose substitution and DP. Furthermore, the data suggests that the enzyme-generated MOS may be useful as potent additives to dietary foods.


Assuntos
Aspergillus niger , Prebióticos , Aspergillus niger/genética , Hidrólise , Mananas , Oligossacarídeos , beta-Manosidase/genética
2.
BMC Genomics ; 22(1): 679, 2021 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-34548025

RESUMO

BACKGROUND: Aspergillus niger is a ubiquitous filamentous fungus widely employed as a cell factory thanks to its abilities to produce a wide range of organic acids and enzymes. Its genome was one of the first Aspergillus genomes to be sequenced in 2007, due to its economic importance and its role as model organism to study fungal fermentation. Nowadays, the genome sequences of more than 20 A. niger strains are available. These, however, do not include the neotype strain CBS 554.65. RESULTS: The genome of CBS 554.65 was sequenced with PacBio. A high-quality nuclear genome sequence consisting of 17 contigs with a N50 value of 4.07 Mbp was obtained. The assembly covered all the 8 centromeric regions of the chromosomes. In addition, a complete circular mitochondrial DNA assembly was obtained. Bioinformatic analyses revealed the presence of a MAT1-2-1 gene in this genome, contrary to the most commonly used A. niger strains, such as ATCC 1015 and CBS 513.88, which contain a MAT1-1-1 gene. A nucleotide alignment showed a different orientation of the MAT1-1 locus of ATCC 1015 compared to the MAT1-2 locus of CBS 554.65, relative to conserved genes flanking the MAT locus. Within 24 newly sequenced isolates of A. niger half of them had a MAT1-1 locus and the other half a MAT1-2 locus. The genomic organization of the MAT1-2 locus in CBS 554.65 is similar to other Aspergillus species. In contrast, the region comprising the MAT1-1 locus is flipped in all sequenced strains of A. niger. CONCLUSIONS: This study, besides providing a high-quality genome sequence of an important A. niger strain, suggests the occurrence of genetic flipping or switching events at the MAT1-1 locus of A. niger. These results provide new insights in the mating system of A. niger and could contribute to the investigation and potential discovery of sexuality in this species long thought to be asexual.


Assuntos
Aspergillus niger , Genes Fúngicos Tipo Acasalamento , Aspergillus niger/genética , Sequência de Bases , Mapeamento Cromossômico , Genômica
3.
Appl Microbiol Biotechnol ; 105(20): 7731-7741, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34568964

RESUMO

Iridoids are widely found from species of Bignoniaceae family and exhibit several biological activities, such as anti-inflammatory, antimicrobial, antioxidant, and antitumor. Specioside is an iridoid found from Tabebuia species, mainly in Tabebuia aurea. Thus, here fungus-mediated biotransformation of the iridoid specioside was investigated by seven fungi. The fungus-mediated biotransformation reactions resulted in a total of nineteen different analogs by fungus Aspergillus niger, Aspergillus flavus, Aspergillus japonicus, Aspergillus terreus, Aspergillus niveus, Penicillium crustosum, and Thermoascus aurantiacus. Non-glycosylated specioside was the main metabolite observed. The other analogs were yielded from ester hydrolysis, hydroxylation, methylation, and hydrogenation reactions. The non-glycosylated specioside and coumaric acid were yielded by all fungi-mediated biotransformation. Thus, fungus applied in this study showed the ability to perform hydroxylation and glycosidic, as well as ester hydrolysis reactions from glycosylated iridoid. KEY POINTS: • The biotransformation of specioside by seven fungi yielded nineteen analogs. • The non-glycosylated specioside was the main analog obtained. • Ester hydrolysis, hydroxylation, methylation, and hydrogenation reactions were observe.


Assuntos
Aspergillus niger , Iridoides , Aspergillus , Biotransformação , Glucosídeos Iridoides , Penicillium
4.
Molecules ; 26(17)2021 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-34500567

RESUMO

Cinnamomum camphora L. is grown as an ornamental plant, used as raw material for furniture, as a source of camphor, and its essential oil can be used as an important source for perfume as well as alternative medicine. A comparative investigation of essential oil compositions and antimicrobial activities of different tissues of C. camphora was carried out. The essential oils were extracted by hydrodistillation with a Clevenger apparatus and their compositions were evaluated through gas chromatography-mass spectrometry (GC-MS), enantiomeric composition by chiral GC-MS, and antimicrobial properties were assayed by measuring minimum inhibitory concentrations (MICs). Different plant tissues had different extraction yields, with the leaf having the highest yield. GC-MS analysis revealed the presence of 18, 75, 87, 67, 67, and 74 compounds in leaf, branch, wood, root, leaf/branch, and leaf/branch/wood, respectively. The significance of combining tissues is to enable extraction of commercial quality essential oils without the need to separate them. The oxygenated monoterpene camphor was the major component in all tissues of C. camphora except for safrole in the root. With chiral GC-MS, the enantiomeric distributions of 12, 12, 13, 14, and 14 chiral compounds in branch, wood, root, leaf/branch, and leaf/branch/wood, respectively, were determined. The variation in composition and enantiomeric distribution in the different tissues of C. camphora may be attributed to the different defense requirements of these tissues. The wood essential oil showed effective antibacterial activity against Serratia marcescens with an MIC of 39.1 µg/mL. Similarly, the mixture of leaf/branch/wood essential oils displayed good antifungal activity against Aspergillus niger and Aspergillus fumigatus while the leaf essential oil was notably active against Trichophyton rubrum. C. camphora essential oils showed variable antimicrobial activities against dermal and pulmonary-borne microbes.


Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Cinnamomum camphora/química , Óleos Voláteis/química , Óleos Voláteis/farmacologia , Antifúngicos/química , Antifúngicos/farmacologia , Arthrodermataceae/efeitos dos fármacos , Aspergillus niger/efeitos dos fármacos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Testes de Sensibilidade Microbiana/métodos , Monoterpenos/química , Monoterpenos/farmacologia , Folhas de Planta/química , Óleos Vegetais/química , Óleos Vegetais/farmacologia , Raízes de Plantas/química
5.
Appl Microbiol Biotechnol ; 105(16-17): 6477-6488, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34424384

RESUMO

Co-existence of toxic metals causes complex toxicity to microorganisms during bioremediation in water and soil. This study investigated the immobilization of Pb2+ and Cd2+ by fungus Aspergillus niger, which has been widely applied to environmental remediation. Five treatments were set, i.e., CK (no toxic metals), Pb2+ only, Cd2+ only, Pb2+/Cd2+ = 1:1(molar ratio), and Pb2+/Cd2+ = 2:1. Cadmium induced strong toxicity to the fungus, and maintained the high toxicity during incubation. However, as Pb/Cd ratio increased from 0 to 2, the removal rates of Cd2+ by A. niger were raised from 30 to 50%. The elevated activities of pyruvate dehydrogenase (PDH) and citrate synthetase (CS) enzymes confirmed that Pb addition could stimulate the growth of A. niger. For instance, citric acid concentrations and CS activities were 463.22 mg/L and 78.37 nmol/min/g, respectively, during 3-day incubation as Pb/Cd = 1. However, these two values were as low as ~ 50 with addition of only Cd. It was hence assumed that appropriate co-existence of Pb2+ enhanced microbial activity by promoting TCA cycle of the fungus. Moreover, the SEM analysis and geochemical modeling demonstrated that Pb2+ cations were more easily adsorbed and mineralized on A. niger with respect to Cd2+. Therefore, instead of intensifying metal toxicity, the addition of appropriate Pb actually weakened Cd toxicity to the fungus. This study sheds a bright future on application of A. niger to the remediation of polluted water with co-existence of Pb and Cd. KEY POINTS: • Cd2+ significantly inhibited P consumption, suggesting its high toxicity to A. niger. • Pb2+ stimulated the growth of A. niger by promoting TCA cycle in the cells. • Cd2+ removal by A. niger were improved with co-existence of Pb2+.


Assuntos
Aspergillus niger , Cádmio , Bioacumulação , Biodegradação Ambiental , Cádmio/análise , Cádmio/toxicidade , Chumbo/toxicidade
6.
J Microbiol ; 59(9): 819-826, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34382148

RESUMO

Phosphate solubilizing fungi (PSF) have been widely applied to dissolve insoluble phosphates (IPs). However, the PSF usually demonstrates a different phosphate solubilizing capacity for various IPs. This study explored the mechanisms of Aspergillus niger for the dissolution of ferric phosphate (FePO4, Fe-P), and tricalcium phosphate (Ca3[PO4]2, Ca-P) regarding the tricarboxylic acid (TCA) cycle. Aspergillus niger has higher phosphorus (P) content released from Ca-P, reached the maximum value of 861 mg/L after seven days of incubation, compared with the 169 mg/L from Fe-P. Oxalic acid promoted the release of P from Ca-P through the formation of calcium oxalate. The presence of Fe-P can stimulate A. niger to secrete large amounts of citric acid, confirmed by the enhancement of citrate synthase (CS) activity. However, citric acid only promotes 0.5% of P released from Fe-P. Meanwhile, although oxalic acid still dominates the release of P from Fe-P, its abundance was significantly declined. In contrast, oxalic acid also shows a higher P release ratio in Ca-P than citric acid, i.e., 36% vs. 22%. This study points to the future usage of A. niger to dissolve IPs in soil required to enhance oxalic acid secretion.


Assuntos
Aspergillus niger/metabolismo , Fosfatos de Cálcio/metabolismo , Compostos Férricos/metabolismo , Aspergillus niger/genética , Fosfatos de Cálcio/química , Citrato (si)-Sintase/genética , Citrato (si)-Sintase/metabolismo , Ácido Cítrico/metabolismo , Compostos Férricos/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Ácido Oxálico/metabolismo , Solo/química
7.
Molecules ; 26(16)2021 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-34443650

RESUMO

A chemical investigation into endozoic fungus Aspergillus niger L14 derived from the marine sponge of Reniera japonica collected off Xinghai Bay (China) resulted in the isolation of two dimeric naphtho-γ-pyrones, fonsecinone A (1) and isoaurasperone A (2). Through a combination of ECD spectra and X-ray diffraction analysis, the chiral axes of compounds 1 and 2 were unambiguously determined as Rα-configurations. Bioassay results indicated that these substances exhibited remarkably inhibitory effects on human pathogens Helicobacter pylori G27 and 159 with MIC values of ≤4 µg/mL, which are similar to those of the positive control, ampicillin sodium. To the best of our knowledge, this is the first report on absolute configuration of 1 and crystallographic data of 2, as well as their potent anti-H. pylori activities.


Assuntos
Antibacterianos/metabolismo , Antibacterianos/farmacologia , Aspergillus niger/metabolismo , Helicobacter pylori/efeitos dos fármacos , Poríferos/metabolismo , Ampicilina/farmacologia , Animais , Testes de Sensibilidade Microbiana , Pironas/metabolismo , Pironas/farmacologia
8.
Molecules ; 26(16)2021 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-34443666

RESUMO

The assertion made by Wu et al. that aromaticity may have considerable implications for molecular design motivated us to use nucleus-independent chemical shifts (NICS) as an aromaticity criterion to evaluate the antifungal activity of two series of indol-4-ones. A linear regression analysis of NICS and antifungal activity showed that both tested variables were significantly related (p < 0.05); when aromaticity increased, the antifungal activity decreased for series I and increased for series II. To verify the validity of the obtained equations, a new set of 44 benzofuran-4-ones was designed by replacing the nitrogen atom of the five-membered ring with oxygen in indol-4-ones. The NICS(0) and NICS(1) of benzofuran-4-ones were calculated and used to predict their biological activities using the previous equations. A set of 10 benzofuran-4-ones was synthesized and tested in eight human pathogenic fungi, showing the validity of the equations. The minimum inhibitory concentration (MIC) in yeasts was 31.25 µg·mL-1 for Candida glabrata, Candida krusei and Candida guilliermondii with compounds 15-32, 15-15 and 15-1. The MIC for filamentous fungi was 1.95 µg·mL-1 for Aspergillus niger for compounds 15-1, 15-33 and 15-34. The results obtained support the use of NICS in the molecular design of compounds with antifungal activity.


Assuntos
Antifúngicos/farmacologia , Benzofuranos/farmacologia , Fungos/efeitos dos fármacos , Antifúngicos/química , Aspergillus niger/efeitos dos fármacos , Aspergillus niger/patogenicidade , Benzofuranos/química , Candida/efeitos dos fármacos , Candida/patogenicidade , Humanos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Pichia/efeitos dos fármacos , Pichia/patogenicidade , Hidrocarbonetos Policíclicos Aromáticos/química , Hidrocarbonetos Policíclicos Aromáticos/farmacologia
9.
Environ Sci Pollut Res Int ; 28(33): 44622-44637, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34215982

RESUMO

In the twenty-first century, the increasing demand for electrical and electronic equipment (EEE) has caused its quick update and the shortening of its service life span. As a consequence, a large number of waste electrical and electronic equipment (WEEE) needs to be processed and recycled. As an environmentally friendly method, biometallurgy has received extensive attention in the disposal of WEEE in recent years. Aspergillus niger is an acid-producing fungus with a potential applicability to improve metals' recycling efficiency. This review article describes the latest statistical status of WEEE and presents the latest progress of various metallurgical methods involved in WEEE recycling for metal recovery. Moreover, based on the summary and comparison towards studies have been reported for bioleaching metals from WEEE by A. niger, the bioleaching mechanisms and the bioleaching methods are explained, as well as the effects of process parameters on the performance of the bioleaching process are also discussed. Some insights and perspectives are provided for A. niger to be applied to industrial processing scale.


Assuntos
Resíduo Eletrônico , Aspergillus niger , Resíduo Eletrônico/análise , Eletrônica , Metais , Reciclagem
10.
Enzyme Microb Technol ; 149: 109833, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34311878

RESUMO

Endoglucanase and xylanase are critical enzymes for liquefaction and enzyme hydrolysis of high solids lignocellulosic biomass to facilitate its transport and production of desired derived products. Here is reported how combinations of different spore concentrations and pH influence microbial morphology, and how this may be used to direct expression and secretion of enzymes by Aspergillus niger. While xylanase production is not affected by A. niger morphology changes, endoglucanase production is enhanced under conditions of lower stress and by morphology that results in pellets. ß-glucosidase production is enhanced under dispersed morphology, which results in up to fourfold increase of this enzyme production under the tested experimental conditions. A morphologic scale (Y) is proposed based on a form factor that considers the size and frequency of each morphology class, and that points to conditions that result in high selectivity for either endoglucanase or ß-glucosidase production. An equation proposed to relate enzyme activity to morphology provides a useful tool for tuning enzyme production of A. niger, where morphology is a first indication of relative enzyme activities in a fermentation broth.


Assuntos
Celulase , Celulose , Aspergillus niger/genética , Aspergillus niger/metabolismo , Celulase/genética , Celulose/metabolismo , Fermentação , Hidrólise
11.
Appl Microbiol Biotechnol ; 105(13): 5553-5564, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34236481

RESUMO

Aspergillus niger is a filamentous fungus well known for its ability to produce a wide variety of pectinolytic enzymes, which have many applications in the industry. The transcriptional activator GaaR is induced by 2-keto-3-deoxy-L-galactonate, a compound derived from D-galacturonic acid, and plays a major role in the regulation of pectinolytic genes. The requirement for inducer molecules can be a limiting factor for the production of enzymes. Therefore, the generation of chimeric transcription factors able to activate the expression of pectinolytic genes by using underutilized agricultural residues would be highly valuable for industrial applications. In this study, we used the CRISPR/Cas9 system to generate three chimeric GaaR-XlnR transcription factors expressed by the xlnR promoter by swapping the N-terminal region of the xylanolytic regulator XlnR to that of the GaaR in A. niger. As a test case, we constructed a PpgaX-hph reporter strain to evaluate the alteration of transcription factor specificity in the chimeric mutants. Our results showed that the chimeric GaaR-XlnR transcription factor was induced in the presence of D-xylose. Additionally, we generated a constitutively active GaaR-XlnR V756F version of the most efficient chimeric transcription factor to better assess its activity. Proteomics analysis confirmed the production of several pectinolytic enzymes by ΔgaaR mutants carrying the chimeric transcription factor. This correlates with the improved release of D-galacturonic acid from pectin by the GaaR-XlnR V756F mutant, as well as by the increased L-arabinose release from the pectin side chains by both chimeric mutants under inducing condition, which is required for efficient degradation of pectin. KEY POINTS: • Chimeric transcription factors were generated by on-site mutations using CRISPR/Cas9. • PpgaX-hph reporter strain allowed for the screening of functional GaaR-XlnR mutants. • Chimeric GaaR-XlnR induced pectinolytic activities in the presence of D-xylose.


Assuntos
Aspergillus niger , Fatores de Transcrição , Aspergillus niger/genética , Aspergillus niger/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Regulação Fúngica da Expressão Gênica , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Xilose
12.
Appl Microbiol Biotechnol ; 105(13): 5529-5539, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34254155

RESUMO

Aspergillus niger is widely used for the efficient production of organic acids and enzyme preparations. However, this organism lacks basic genetic elements for dynamic control, especially inducible promoters that can respond to specific environmental signals. Since these are desirable for better adaptation of fermentation to large-scale industrial production, herein, we have identified the two first hypoxia-inducible promoters in A. niger, PsrbB and PfhbA. Their performance under high or low oxygen conditions was monitored using two reporter proteins, green fluorescent protein (EGFP) and ß-glucuronidase (GUS). For comparison, basal expression of the general strong promoter PgpdA was lower than PsrbB but higher than PfhbA. However, under hypoxia, both promoters showed higher expression than under hyperoxia, and these values were also higher than those observed for PgpdA. For PsrbB, strength under hypoxia was ~2-3 times higher than under hyperoxia (for PfhbA, 3-9 times higher) and ~2.5-5 times higher than for PgpdA (for PfhbA, 2-3 times higher). Promoter truncation analysis showed that the PsrbB fragment -1024 to -588 bp is the core region that determines hypoxia response. KEY POINTS: The first identification of two hypoxia-inducible promoters in A. niger is a promising tool for modulation of target genes under hypoxia. Two reporter genes revealed a different activity and responsiveness to hypoxia of PfhbA and PsrbB promoters, which is relevant for the development of dynamic metabolic regulation of A. niger fermentation. PsrbB promoter truncation and bioinformatics analysis is the foundation for further research.


Assuntos
Aspergillus niger , Hipóxia , Aspergillus niger/genética , Genes Reporter , Proteínas de Fluorescência Verde/genética , Humanos , Regiões Promotoras Genéticas
13.
Chest ; 160(1): e39-e44, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34246387

RESUMO

CASE PRESENTATION: A 65-year-old man presented with shortness of breath, gradually worsening for the previous 2 weeks, associated with dry cough, sore throat, and diarrhea. He denied fever, chills, chest pain, abdominal pain, nausea, or vomiting. He did not have any sick contacts or travel history outside of Michigan. His medical history included hypertension, diabetes mellitus, chronic kidney disease, morbid obesity, paroxysmal atrial fibrillation, and tobacco use. He was taking amiodarone, carvedilol, furosemide, pregabalin, and insulin. The patient appeared to be in mild respiratory distress. He was afebrile and had saturation at 93% on 3 L of oxygen, heart rate of 105 beats/min, BP of 145/99 mm Hg, and respiratory rate of 18 breaths/min. On auscultation, there were crackles on bilateral lung bases and chronic bilateral leg swelling with hyperpigmented changes. His WBC count was 6.0 K/cumm (3.5 to 10.6 K/cumm) with absolute lymphocyte count 0.7 K/cumm (1.0 to 3.8 K/cumm); serum creatinine was 2.81 mg/dL (0.7 to 1.3 mg/dL). He had elevated inflammatory markers (serum ferritin, C-reactive protein, lactate dehydrogenase, D-dimer, and creatinine phosphokinase). Chest radiography showed bilateral pulmonary opacities that were suggestive of multifocal pneumonia (Fig 1). Nasopharyngeal swab for SARS-CoV-2 was positive. Therapy was started with ceftriaxone, doxycycline, hydroxychloroquine, and methylprednisolone 1 mg/kg IV for 3 days. By day 3 of hospitalization, he required endotracheal intubation, vasopressor support, and continuous renal replacement. Blood cultures were negative; respiratory cultures revealed only normal oral flora, so antibiotic therapy was discontinued. On day 10, WBC count increased to 28 K/cumm, and chest radiography showed persistent bilateral opacities with left lower lobe consolidation. Repeat respiratory cultures grew Pseudomonas aeruginosa (Table 1). Antibiotic therapy with IV meropenem was started. His condition steadily improved; eventually by day 20, he was off vasopressors and was extubated. However, on day 23, he experienced significant hemoptysis that required reintubation and vasopressor support.


Assuntos
Aspergillus niger/isolamento & purificação , COVID-19 , Hemoptise , Aspergilose Pulmonar Invasiva , Pseudomonas aeruginosa/isolamento & purificação , SARS-CoV-2/isolamento & purificação , Superinfecção , Voriconazol/administração & dosagem , Idoso , Antifúngicos/administração & dosagem , COVID-19/complicações , COVID-19/diagnóstico , COVID-19/fisiopatologia , COVID-19/terapia , Deterioração Clínica , Estado Terminal/terapia , Procedimentos Clínicos , Diagnóstico Diferencial , Hemoptise/diagnóstico , Hemoptise/etiologia , Hemoptise/terapia , Humanos , Aspergilose Pulmonar Invasiva/complicações , Aspergilose Pulmonar Invasiva/diagnóstico , Aspergilose Pulmonar Invasiva/fisiopatologia , Pulmão/diagnóstico por imagem , Pulmão/fisiopatologia , Masculino , Radiografia Torácica/métodos , Respiração Artificial/métodos , Superinfecção/diagnóstico , Superinfecção/microbiologia , Superinfecção/fisiopatologia , Superinfecção/terapia , Tomografia Computadorizada por Raios X/métodos , Resultado do Tratamento
14.
J Chromatogr A ; 1653: 462388, 2021 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-34280789

RESUMO

In this study, an enzyme immobilization method for the effective biotransformation of ginsenoside Rb1 to impart activity and stability was developed. Using a hydrolase enzyme model, ß-glucosidase from Aspergillus niger, immobilization within chemically affinity-linked amino-based silica provided an immobilization efficiency 5.86-fold higher than that of free enzyme. Compared with the free enzyme, the immobilized enzyme functioned optimally at a wider pH range and had higher thermostability. The optimum pH for the free and immobilized enzymes was 5.5. The optimal reaction temperature of the immobilized enzyme was 45 °C, which was 5 °C higher than that of the free enzyme. The Michaelis constant (Km) values before and after immobilization were 0.482 mmol•L-1 and 0.387 mmol•L-1, respectively. The catalytic rate (Kcat) for the immobilized and free enzymes was 22.269 mmol•L-1and 8.800 mmol•L-1, respectively, and the catalytic efficiency (Kcat/Km) activity of the immobilized enzyme was 3.30-fold higher than that of the free enzyme. The immobilized enzyme could preserve 97 % of the activity after 45 cycles of repeated use. The high catalytic activity and significant operational stability are beneficial for industrial applications.


Assuntos
Aspergillus niger , Ginsenosídeos , Dióxido de Silício , beta-Glucosidase , Aspergillus niger/metabolismo , Biotransformação , Estabilidade Enzimática , Enzimas Imobilizadas/metabolismo , Ginsenosídeos/química , Ginsenosídeos/metabolismo , Concentração de Íons de Hidrogênio , Dióxido de Silício/química , Temperatura , beta-Glucosidase/metabolismo
15.
Bioresour Technol ; 337: 125462, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34320742

RESUMO

The role and mechanism of elagitannase is misunderstood because it exhibited different activities due to the low purity or complexity of substrates, and there is no available information about the biochemical, physicochemical and molecular characteristics of the enzyme. This study was aimed to obtain enzymatic extracts by Aspergillus niger GH1 in solid-state fermentation, using dextrose and ellagitannins as inducers of ellagitannase. Protein and bioinformatic analysis were performed to identify the protein sequence expressed in terms of culture conditions. The presence of ellagitannins increased ellagitannase activity 1143-fold compared to dextrose. The higher ellagitannase activity was found at 18 h of culture (1143.30 U g-1PE). Three groups of proteins were identified in both cultures: ß-glucosidase, phospholipase C, and triacylglycerol lipase. However, only phospholipase C was overexpressed with ellagitannins as inducers, showing the most spontaneous reaction with punicalagin (ΔG -8.56). These results suggest that phospholipase could be involved in ellagitannins biosynthesis.


Assuntos
Ácido Elágico , Taninos Hidrolisáveis , Aspergillus niger/metabolismo , Fermentação , Taninos Hidrolisáveis/metabolismo
16.
Anal Bioanal Chem ; 413(17): 4407-4416, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34081166

RESUMO

A novel copper-based metal-organic framework (Cu-MOF) with a large specific surface area and high porosity was synthesized. The Cu-MOF was a good peroxidase-mimicking enzyme and showed a high affinity with hydrogen peroxide in a wide pH range. The catalytic mechanism of Cu-MOF has been studied further based on comparing the characteristic of the Cu-MOF with some isomorphic MOFs. The catalytic activity center of Cu-MOF was determined to be the cupric ion rather than the ligand, which effectively promoted the generation of free radicals and electron transfer in the reaction progress. The high affinity of Cu-MOF to hydrogen peroxide proved it as an ideal catalyst for the chemiluminescence (CL) reaction involving hydrogen peroxide. Therefore, the CL method with high sensitivity could be established for detecting various substrates. A double-enzyme CL glucose biosensing platform was constructed for the determination of serum glucose employing the peroxidase-mimicking properties of Cu-MOF as well as glucose oxidase (GOx).


Assuntos
Técnicas Biossensoriais/métodos , Glicemia/análise , Cobre/química , Estruturas Metalorgânicas/química , Aspergillus niger/enzimologia , Catálise , Glucose Oxidase/química , Humanos , Peróxido de Hidrogênio/química , Limite de Detecção , Medições Luminescentes/métodos , Modelos Moleculares , Peroxidase/química
17.
Microb Biotechnol ; 14(4): 1683-1698, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34114741

RESUMO

Fungi produce a wide range of enzymes that allow them to grow on diverse plant biomass. Wheat bran is a low-cost substrate with high potential for biotechnological applications. It mainly contains cellulose and (arabino)xylan, as well as starch, proteins, lipids and lignin to a lesser extent. In this study, we dissected the regulatory network governing wheat bran degradation in Aspergillus niger to assess the relative contribution of the regulators to the utilization of this plant biomass substrate. Deletion of genes encoding transcription factors involved in (hemi-)cellulose utilization (XlnR, AraR, ClrA and ClrB) individually and in combination significantly reduced production of polysaccharide-degrading enzymes, but retained substantial growth on wheat bran. Proteomic analysis suggested the ability of A. niger to grow on other carbon components, such as starch, which was confirmed by the additional deletion of the amylolytic regulator AmyR. Growth was further reduced but not impaired, indicating that other minor components provide sufficient energy for residual growth, displaying the flexibility of A. niger, and likely other fungi, in carbon utilization. Better understanding of the complexity and flexibility of fungal regulatory networks will facilitate the generation of more efficient fungal cell factories that use plant biomass as a substrate.


Assuntos
Aspergillus niger , Regulação Fúngica da Expressão Gênica , Aspergillus niger/genética , Aspergillus niger/metabolismo , Biomassa , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Polissacarídeos , Proteômica
18.
Microb Biotechnol ; 14(4): 1747-1756, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34115922

RESUMO

There are a need for novel, economical and efficient metal processing technologies to improve critical metal sustainability, particularly for cobalt and nickel which have extensive applications in low-carbon energy technologies. Fungal metal biorecovery processes show potential in this regard and the products of recovery are also industrially significant. Here we present a basis for selective biorecovery of Co and Ni oxalates and phosphates using reactive spent Aspergillus niger culture filtrate containing mycogenic oxalate and phosphate solubilized from struvite. Selective precipitation of oxalates was achieved by adjusting phosphate-laden filtrates to pH 2.5 prior to precipitation. Co recovery at pH 2.5 was high with a maximum of ~96% achieved, while ~60% Ni recovery was achieved, yielding microscale polyhedral biominerals. Co and Ni phosphates were precipitated at pH 7.5, following prior oxalate removal, resulting in near-total Co recovery (>99%), while Ni phosphate yields were also high with a recovery maximum of 83.0%.


Assuntos
Cobalto , Níquel , Aspergillus niger/genética , Biomineralização , Fosfatos
19.
Ultrason Sonochem ; 76: 105636, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34192660

RESUMO

For the first time, this study addresses the intensification of supercritical carbon dioxide (SC-CO2) treatments using high-power ultrasound (HPU) for the inactivation of fungal (Aspergillus niger) and bacterial (Clostridium butyricum) spores in oil-in-water emulsions. The inactivation kinetics were analyzed at different pressures (100, 350 and 550 bar) and temperatures (50, 60, 70, 80, 85 °C), depending on the microorganism, and compared to the conventional thermal treatment. The inactivation kinetics were satisfactorily described using the Weibull model. Experimental results showed that SC-CO2 enhanced the inactivation level of both spores when compared to thermal treatments. Bacterial spores (C.butyricum) were found to be more resistant to SC-CO2 + HPU, than fungal (A.niger) ones, as also observed in the thermal and SC-CO2 treatments. The application of HPU intensified the SC-CO2 inactivation of C.butyricum spores, e.g. shortening the total inactivation time from 10 to 3 min at 85 °C. However, HPU did not affect the SC-CO2 inactivation of A.niger spores. The study into the effect of a combined SC-CO2 + HPU treatment has to be necessarily extended to other fungal and bacterial spores, and future studies should elucidate the impact of HPU application on the emulsion's stability.


Assuntos
Dióxido de Carbono/farmacologia , Lipídeos/química , Viabilidade Microbiana/efeitos dos fármacos , Esporos Bacterianos/efeitos dos fármacos , Esporos Fúngicos/efeitos dos fármacos , Ondas Ultrassônicas , Aspergillus niger/efeitos dos fármacos , Aspergillus niger/fisiologia , Clostridium butyricum/efeitos dos fármacos , Clostridium butyricum/fisiologia , Emulsões , Esporos Bacterianos/fisiologia , Esporos Fúngicos/fisiologia
20.
Sci Total Environ ; 790: 148151, 2021 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-34111782

RESUMO

Using Aspergillus niger (A. niger) to produce low-concentration organic acids is challenging for dissolving In3O2 from waste LCD (liquid crystal display) panels with high toxicity. In this study, three bioleaching approaches from the general and the optimized fermentation systems were investigated respectively to compare indium recovery effects and firstly clarified its bioleaching mechanism. The indium bioleaching efficiency can be improved from 12.3% to 100% by fermentation method optimization. Carboxy groups from organic acids and proteins were the critical substances to release H+ for leaching indium mainly competed with iron via reactions analysis. The effective components increased after optimizing, including the dissociative H+ concentration, the effective carboxyl groups for leaching metal oxides, and the output of oxalic acid. A. niger biomass prevented the contact between H+ and In3O2 and adsorbed In3+ adverse to indium recovery. The bioleaching effects of fermentation broth for indium can be further promoted by controlling bioleaching process parameters.


Assuntos
Aspergillus niger , Cristais Líquidos , Fermentação , Índio , Ácido Oxálico
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