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PubMed2000

A glucoamylase::GFP gene fusion to study protein secretion by individual hyphae of Aspergillus niger.

Although Aspergillus niger is used as a host for heterologous protein production, yields are generally lower than those obtained for homologous proteins. Mechanisms of protein secretion and the secretory pathway in filamentous fungi are poorly characterised, although there is evidence to suggest that secretion occurs by a mechanism similar to that in other eukaryotes, but with proteins destined for secretion being directed to the hyphal tip. We report on a method using a glucoamylase: GFP gene fusion which allows us for the first time to monitor, in vivo, protein secretion in A. niger at the single hyphal level. A synthetic green fluorescent protein (sGFP(S65T)) was fused to truncated A. niger glucoamylase (GLA:499). Southern blot analysis of transformants confirmed that the gene fusion had successfully integrated into the A. niger genome. Confocal and fluorescence microscopy revealed that the GLA::GFP fusion protein is fluorescent in A. niger and appears to be directed to the hyphal tip. In young mycelia, hyphal cell wall fluorescence is apparent and immunogold labelling of GFP confirmed that GFP was partially localised within the hyphal cell wall. Using Western blotting, extracellular GLA::GFP was detected only in culture filtrates of young mycelia grown in a soya milk medium. The actin inhibitor latrunculin B was used to disrupt the secretion process, and its effects on the distribution of GLA::GFP were monitored.

Actins↗
PubMed2003

Characterisation of the gptA gene, encoding UDP N-acetylglucosamine: dolichol phosphate N-acetylglucosaminylphosphoryl transferase, from the filamentous fungus, Aspergillus niger.

The production of asparagine (N)-linked oligosaccharides is of vital importance in the formation of glycosylated proteins in eukaryotes and is mediated by the dolichol pathway. As part of studies to allow manipulation of this pathway, the gene coding for the production of the enzyme UDP N-acetylglucosamine: dolichol phosphate N-acetylglucosaminylphosphoryl transferase (GPT), catalysing the first step in the assembly of dolichol-linked oligosaccharides, was cloned from the filamentous fungus Aspergillus niger. Degenerate-PCR was used to amplify a 470-bp fragment of the gene, which was labelled as a probe to obtain a full-length clone from a genomic library of A. niger. This contained a 1557-bp open reading frame encoding a highly hydrophobic protein of 468 amino acids with a predicted molecular weight of 51.4 kDa. The gene contained two intron sequences and putative dolichol recognition sites (PDRSs) were present in the deduced amino acid sequence. Comparison with other eukaryotic GPTs revealed the A. niger GPT to share 45-47% identity with yeasts (Saccharomyces cerevisiae and Schizosaccharomyces pombe) and 41-42% identity with mammals (mouse, hamster, human). Nested-PCR of a cDNA library was used to confirm the position of an intron. A complete cDNA clone of A. niger gpt was obtained by employing a recombinant PCR approach. This was used to rescue a conditional lethal mutant of S. cerevisiae carrying a dysfunctional gpt gene by heterologous expression, confirming that the gpt genes from A. niger and S. cerevisiae are functionally equivalent.

Amino Acid Sequence↗
PubMed2002

The Aspergillus niger faeB gene encodes a second feruloyl esterase involved in pectin and xylan degradation and is specifically induced in the presence of aromatic compounds.

The faeB gene encoding a second feruloyl esterase from Aspergillus niger has been cloned and characterized. It consists of an open reading frame of 1644 bp containing one intron. The gene encodes a protein of 521 amino acids that has sequence similarity to that of an Aspergillus oryzae tannase. However, the encoded enzyme, feruloyl esterase B (FAEB), does not have tannase activity. Comparison of the physical characteristics and substrate specificity of FAEB with those of a cinnamoyl esterase from A. niger [Kroon, Faulds and Williamson (1996) Biotechnol. Appl. Biochem. 23, 255-262] suggests that they are in fact the same enzyme. The expression of faeB is specifically induced in the presence of certain aromatic compounds, but not in the presence of other constituents present in plant-cell-wall polysaccharides such as arabinoxylan or pectin. The expression profile of faeB in the presence of aromatic compounds was compared with the expression of A. niger faeA, encoding feruloyl esterase A (FAEA), and A. niger bphA, the gene encoding a benzoate-p-hydroxylase. All three genes have different subsets of aromatic compounds that induce their expression, indicating the presence of different transcription activating systems in A. niger that respond to aromatic compounds. Comparison of the activity of FAEA and FAEB on sugar-beet pectin and wheat arabinoxylan demonstrated that they are both involved in the degradation of both polysaccharides, but have opposite preferences for these substrates. FAEA is more active than FAEB towards wheat arabinoxylan, whereas FAEB is more active than FAEA towards sugar-beet pectin.

Amino Acid Sequence↗
PubMed1998

Metabolism of carbofuran by Aspergillus niger and Fusarium graminearum.

Metabolism of carbofuran in pure liquid cultures of A. niger and F. graminearum was investigated. Carbofuran and its metabolites were analyzed by HPLC and TLC. The average recoveries of carbofuran, 3-hydroxycarbofuran, 3-ketocarbofuran, and 3-ketocarbofuran phenol from fungi media were found to be 88.65, 86.19, 75.48, and 80.48%, while their detection limits were 0.035, 0.031, 0.015 and 0.140 ppm, respectively. The data showed that A. niger was capable of degrading carbofuran more faster than F. graminearum. Carbofuran disappeared biexponentially from the liquid culture media of both fungi. The terminal half-life values of carbofuran were 10.4 and 12 days in the media of A. niger and F. graminearum, respectively. The amounts of carbofuran reached 15.56 and 19.71% of the applied dose after 21 days in case of A. niger and F. graminearum, respectively. Carbofuran was biotransformed to 3-hydroxycarbofuran, 3-ketocarbofuran, and 3-ketocarbofuran phenol. The percentages of the major metabolite, 3-hydroxycarbofuran were 47.72 and 7.77% in case of A. niger and F. graminearum after 21 days, respectively.

Aspergillus niger↗
PubMed1995

Cloning and characterization of the NADPH cytochrome P450 oxidoreductase gene from the filamentous fungus Aspergillus niger.

In this paper, we describe the cloning and molecular characterization of the Aspergillus niger cytochrome P450 reductase (CPR) gene, cprA. Attempts to clone the cprA gene by heterologous hybridization techniques were unsuccessful. Using the polymerase chain reaction (PCR) with degenerate primers based on conserved regions found in cpr genes from other organisms, we were able to isolate a fragment that contained part of the gene. With the aid of this fragment, a genomic fragment containing the entire coding region and 5' and 3' untranslated ends of the cprA gene was isolated and sequenced. The cprA gene was introduced in multiple copies in A. niger strain N402 using the amdS transformation system. One of the resulting transformants, AB2-2, showed a 14-fold increase in CPR activity, indicating that the cloned cprA gene is functional. We analyzed the induction of cprA gene expression by several generally used cytochrome P450 inducers but did not find any induction of cprA gene expression. However, A. niger cprA gene expression could be induced by benzoic acid, which is the substrate of the highly inducible A. niger cytochrome P450 gene, bphA (cyp53). On the basis of a comparison of the deduced protein sequence of the A. niger cprA gene with CPR proteins isolated from other organisms, the structure-function relationship of some conserved regions is discussed.

Amidohydrolases↗
PubMed2002

Evaluation of the Quality Assurance Project and BASICS Joint Project in Niger.

OBJECTIVE: The 1998 evaluation sought to assess the Quality Assurance Project (QAP) in Niger since 1993 and the degree of quality assurance institutionalization in the Tahoua Department, and to summarize lessons from introducing the Integrated Management of Childhood Illness (IMCI) guidelines in a quality management (QM) environment. DESIGN: This evaluation collected data from interviews with staff and managers, from focus groups conducted in the communities, and from medical records. The data were then compared with three sources of evaluation criteria. A pre-project assessment provided a baseline across certain impact indicators for tracking progress. Other measures were derived from the objectives and indicators from the QAP/Tahoua project plan, the joint QAP/BASICS (Basic Support for Institutionalizing Child Survival Project) project plan, and from an additional US Agency for International Development (USAID) objective that the joint project be a model for West Africa. SETTING: The evaluation took place in the two departments of Niger in which the joint project was carried out: Tahoua and Dosso. The QA Project launched a pilot program in Niger in 1993 to strengthen newly decentralized regional and district management, and to improve the quality of primary health care in Tahoua. The principal QA Project approach was QM. The BASICS Project became active in Niger in 1995, helping to improve child health services. In 1997, the projects merged in Niger to form the joint QAP/BASICS Project. The Ministry of Public Health (MPH) planned to implement IMCI in 1998, and wished to determine whether QM facilitated the introduction of IMCI. RESULTS: The evaluation team found that QM had been effectively implemented in Tahoua and that there were related improvements in health program indicators. The team also found that the joint project had met most of its objectives and that QM facilitated the introduction of IMCI. A follow-up evaluation 2 years later found continued practice of QM by Nigerien health care providers. CONCLUSION: Several factors contributed to the success of the Tahoua QA program and the joint project: teamwork, focus on patients, clarity of roles through standards, and synergy between the QA Project and the BASICS Project.

Child Health Services↗
PubMed1994

Arabinase gene expression in Aspergillus niger: indications for coordinated regulation.

Aspergillus niger secretes three glycosylated glycosyl hydrolases which are involved in degradation of the plant cell wall polysaccharide L-arabinan: alpha-L-arabinofuranosidases (ABF) A and B, and endo-1,5-alpha-L-arabinase (ABN) A. The nucleotide sequence of the previously cloned gene encoding ABF A (abfA) from A. niger was determined. The coding region contains seven introns. Mature ABF A comprises 603 amino acids with a molecular mass of 65.4 kDa as deduced from the nucleotide sequence. The secreted enzyme is N-glycosylated. The primary structures of the three A. niger arabinases characterized lack similarity. Regulation of arabinase expression upon induction by sugar beet pulp and by L-arabitol was studied as a function of time. This was done in wild-type A. niger as well as in transformants carrying multiple copies of either one of the ABF-encoding genes. Each arabinase gene responded differently upon a mycelial transfer to L-arabitol-containing medium. Extra copies of abfA or abfB led to a decreased expression level of ABN A, though the repression elicited by abfB is stronger and more persistent than that effected by abfA. Multiple copies of both abf genes influence expression of the other ABF similarly, but to a far less pronounced degree than they affect ABN A synthesis. Four putative promoter elements, shared by all three arabinase genes, could be involved in coordination of L-arabinan degradation by A. niger.

Amino Acid Sequence↗
PubMed2006

Database mining and transcriptional analysis of genes encoding inulin-modifying enzymes of Aspergillus niger.

As a soil fungus, Aspergillus niger can metabolize a wide variety of carbon sources, employing sets of enzymes able to degrade plant-derived polysaccharides. In this study the genome sequence of A. niger strain CBS 513.88 was surveyed, to analyse the gene/enzyme network involved in utilization of the plant storage polymer inulin, and of sucrose, the substrate for inulin synthesis in plants. In addition to three known activities, encoded by the genes suc1 (invertase activity; designated sucA), inuE (exo-inulinase activity) and inuA/inuB (endo-inulinase activity), two new putative invertase-like proteins were identified. These two putative proteins lack N-terminal signal sequences and therefore are expected to be intracellular enzymes. One of these two genes, designated sucB, is expressed at a low level, and its expression is up-regulated when A. niger is grown on sucrose- or inulin-containing media. Transcriptional analysis of the genes encoding the sucrose- (sucA) and inulin-hydrolysing enzymes (inuA and inuE) indicated that they are similarly regulated and all strongly induced on sucrose and inulin. Analysis of a DeltacreA mutant strain of A. niger revealed that expression of the extracellular inulinolytic enzymes is under control of the catabolite repressor CreA. Expression of the inulinolytic enzymes was not induced by fructose, not even in the DeltacreA background, indicating that fructose did not act as an inducer. Evidence is provided that sucrose, or a sucrose-derived intermediate, but not fructose, acts as an inducer for the expression of inulinolytic genes in A. niger.

Aspergillus niger↗
PubMed2006

Bioconversion of grape must into modulated gluconic acid production by Aspergillus niger ORS-4.410.

AIMS: Analysis of regulators for modulated gluconic acid production under surface fermentation (SF) condition using grape must as the cheap carbohydrate source, by mutant Aspergillus niger ORS-4.410. Replacement of conventional fermentation condition by solid-state surface fermentation (SSF) for semi-continuous production of gluconic acid by pseudo-immobilization of A. niger ORS-4.410. METHODS AND RESULTS: Grape must after rectification was utilized for gluconic acid production in batch fermentation in SF and SSF processes using mutant strain of A. niger ORS-4.410. Use of rectified grape must led to the improved levels of gluconic acid production (80-85 g l(-1)) in the fermentation medium containing 0.075% (NH4)2HPO4; 0.1% KH2PO4 and 0.015% MgSO4.7H2O at an initial pH 6.6 (+/-0.1) under surface fermentation. Gluconic acid production was modulated by incorporating the 2% soybean oil, 2% starch and 1% H2O2 in fermentation medium at continuously high aeration rate (2.0 l min(-1)). Interestingly, 95.8% yield of gluconic acid was obtained when A. niger ORS-4.410 was pseudo-immobilized on cellulose fibres (bagasse) under SSF. Four consecutive fermentation cycles were achieved with a conversion rate of 0.752-0.804 g g(-1) of substrate into gluconic acid under SSF. CONCLUSIONS: Use of additives modulated the gluconic acid production under SF condition. Semi-continuous production of gluconic acid was achieved with pseudo-immobilized mycelia of A. niger ORS-4.410 having a promising yield (95.8%) under SSF condition. SIGNIFICANCE AND IMPACT OF THE STUDY: The bioconversion of grape must into modulated gluconic acid production under SSF conditions can further be employed in fermentation industries by replacing the conventional carbohydrate sources and expensive, energy consuming fermentation processes.

Aspergillus niger↗
PubMed1992

The polygalacturonases of Aspergillus niger are encoded by a family of diverged genes.

Aspergillus niger produces several polygalacturonases that, with other enzymes, are involved in the degradation of pectin. One of the two previously characterized genes coding for the abundant polygalacturonases I and II (PGI and PGII) found in a commercial pectinase preparation was used as a probe to isolate five more genes by screening a genomic DNA library in phage lambda EMBL4 using conditions of moderate stringency. The products of these genes were detected in the culture medium of Aspergillus nidulans transformants on the basis of activity measurements and Western-blot analysis using a polyclonal antibody raised against PGI. These transformants were, with one exception, constructed using phage DNA. A. nidulans transformants secreted high amounts of PGI and PGII in comparison to the previously characterized A. niger transformants and a novel polygalacturonase (PGC) was produced at high levels by A. nidulans transformed with the subcloned pgaC gene. This gene was sequenced and the protein-coding region was found to be interrupted by three introns; the different intron/exon organization of the three sequenced A. niger polygalacturonase genes can be explained by the gain or loss of two single introns. The pgaC gene encodes a putative 383-amino-acid prepro-protein that is cleaved after a pair of basic amino acids and shows approximately 60% amino acid sequence similarity to the other polygalacturonases in the mature protein. The N-terminal amino acid sequences of the A. niger polygalacturonases display characteristic amino acid insertions or deletions that are also observed in polygalacturonases of phytopathogenic fungi. In the upstream regions of the A. niger polygalacturonase genes, a sequence of ten conserved nucleotides comprising a CCAAT sequence was found, which is likely to represent a binding site for a regulatory protein as it shows a high similarity to the yeast CYC1 upstream activation site recognized by the HAP2/3/4 activation complex.

Amino Acid Sequence↗
PubMed2004

Identification of genes associated with morphology in Aspergillus niger by using suppression subtractive hybridization.

The morphology of citric acid production strains of Aspergillus niger is sensitive to a variety of factors, including the concentration of manganese (Mn(2+)). Upon increasing the Mn(2+) concentration in A. niger (ATCC 11414) cultures to 14 ppb or higher, the morphology switches from pelleted to filamentous, accompanied by a rapid decline in citric acid production. The molecular mechanisms through which Mn(2+) exerts effects on morphology and citric acid production in A. niger cultures have not been well defined, but our use of suppression subtractive hybridization has identified 22 genes responsive to Mn(2+). Fifteen genes were differentially expressed when A. niger was grown in media containing 1,000 ppb of Mn(2+) (filamentous form), and seven genes were expressed in 10 ppb of Mn(2+) (pelleted form). Of the 15 filament-associated genes, seven are novel and eight share 47 to 100% identity with genes from other organisms. Five of the pellet-associated genes are novel, and the other two genes encode a pepsin-type protease and polyubiquitin. All 10 genes with deduced functions are either involved in amino acid metabolism-protein catabolism or cell regulatory processes. Northern blot analysis showed that the transcripts of all 22 genes were rapidly enhanced or suppressed by Mn(2+). Steady-state mRNA levels of six selected filament-associated genes remained high during 5 days of culture in a filamentous state and remained low under pelleted growth conditions. The opposite behavior was observed for four selected pellet-associated genes. The full-length cDNA of the filament-associated clone, Brsa-25, was isolated. Antisense expression of Brsa-25 permitted pelleted growth and increased citrate production at concentrations of Mn(2+) that were higher than the parent strain could tolerate. These results suggest the involvement of the newly isolated genes in the regulation of A. niger morphology.

Amino Acid Sequence↗
PubMed1983

Factors influencing the inhibition of aflatoxin production in corn by Aspergillus niger.

Aspergillus niger, a mold commonly associated with Aspergillus flavus in damaged corn, interferes with the production of aflatoxin when grown with A. flavus on autoclaved corn. The pH of corn-meal disks was adjusted using NaOH-HCl, citric acid-sodium citrate, or a water extract of A. niger fermented corn. Aflatoxin formation was completely inhibited below pH 2.8-3.0, irrespective of the system used for pH adjustment. When grown in association with A. flavus NRRL 6432 on autoclaved corn kernels, A. niger NRRL 6411 lowered substrate pH sufficiently to suppress aflatoxin production. The biodegradation of aflatoxin B1 or its conversion to aflatoxin B2a were eliminated as potential mechanisms by which A. niger reduces aflatoxin contamination. A water extract of corn kernels fermented with A. niger caused an additional inhibition of aflatoxin formation apart from the effects of pH.

Aflatoxin B1↗
PubMed2006

Monitoring the referral system through benchmarking in rural Niger: an evaluation of the functional relation between health centres and the district hospital.

BACKGROUND: The main objective of this study is to establish a benchmark for referral rates in rural Niger so as to allow interpretation of routine referral data to assess the performance of the referral system in Niger. METHODS: Strict and controlled application of existing clinical decision trees in a sample of rural health centres allowed the estimation of the corresponding need for and characteristics of curative referrals in rural Niger. Compliance of referral was monitored as well. Need was matched against actual referral in 11 rural districts. The referral patterns were registered so as to get an idea on the types of pathology referred. RESULTS: The referral rate benchmark was set at 2.5 % of patients consulting at the health centre for curative reasons. Niger's rural districts have a referral rate of less than half this benchmark. Acceptability of referrals is low for the population and is adding to the deficient referral system in Niger. Mortality because of under-referral is highest among young children. CONCLUSION: Referral patterns show that the present programme approach to deliver health care leaves a large amount of unmet need for which only comprehensive first and second line health services can provide a proper answer. On the other hand, the benchmark suggests that well functioning health centres can take care of the vast majority of problems patients present with.

Adolescent↗
PubMed1998

Substrate specificities of alpha-L-arabinofuranosidases produced by two species of Aspergillus niger.

Precise substrate specificities of alpha-L-arabinofuranosidases from Aspergillus niger 5-16 and Aspergillus niger (Megazyme) were investigated. Both enzymes hydrolyzed arabinan and debranched-arabinan at almost the same rate. The alpha-L-Arabinofuranosidase from A. niger (Megazyme) preferentially released arabinosyl side-chains of arabinan. The enzyme tore off both arabinoses attached to O-alpha-L-arabinofuranosyl-(1-->3)-O-beta-D-xylopyranosyl-(1--> 4)-D-xylopyranose and O-beta-D-xylopyranosyl-(1-->4)-[O-alpha-L- arabinofuranosyl-(1-->3)]-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose, but did not tear off xylosyl-arabinose from O-beta-D-xylopyranosyl-(1-->2)-O-alpha-L-arabinofuranosyl-(1-->3) -O-beta-D-xylopyranosyl-(1-->4)-O-beta-D-xylopyranosyl-(1-->4)-D- xylopyranose. The enzyme from A. niger (Megazyme) hydrolyzed methyl 2-O-, methyl 3-O- and methyl 5-O-alpha-L-arabinofuranosyl-alpha-L-arabinofuranosides to arabinose and methyl alpha-L-arabinofuranoside in the order of (1-->5)->(1-->2)->(1-->3)-linkages. On the other hand, alpha-L-arabinofuranosidase from A. niger 5-16 successively liberated the arabinose of arabinan from non-reducing terminals. The enzyme hydrolyzed in the order of (1-->2- > (1-->3)- > (1-->5)-linkages. Both of the enzymes hydrolyzed the (1-->3)-linkage more than the (1-->5)-linkage of methyl 3,5-di-O-alpha-L-arabinofuranosyl-alpha-L-arabinofuranoside.

Arabinonucleosides↗
PubMed2000

Metabolic fate of glutamate and evaluation of flux through the 4-aminobutyrate (GABA) shunt in Aspergillus niger.

Accumulation of GABA and a concurrent block in the Krebs cycle suggest a functional GABA bypass in the acidogenic Aspergillus niger. Apart from the demonstration of enzyme machinery required, a direct measurement of flux through this glutamate decarboxylation loop was attempted. The distribution of carbon from glucose and glutamate was studied using A. niger mycelia grown on different media. The uptake and incorporation of (14)C label into organic acids and amino acids was followed by paper chromatography. Flow of label from glucose into citrate, glutamate and GABA increased in cells harvested at later stages of acidogenic growth. Very little citrate was derived from glutamate while ten times more label reached GABA from labeled glutamate. Radioactivity from L-[U-(14)C]glutamate and not from L-[1-(14)C]glutamate was recovered in GABA. This demonstrated that alpha-decarboxylation of L-glutamate was the source of GABA. Unless grown on GABA, A. niger mycelia did not take up externally supplied GABA. A direct measure of GABA shunt flux was thus not feasible. Therefore a combination of metabolite balance technique and the kinetic approach was applied to evaluate flux from glutamate to succinate in normal and acidogenic A. niger. The flux relative to TCA cycle was estimated by using uptake rate for radiolabeled glutamate, rate of accumulation of certain metabolites and the reactions of GABA metabolism. The analysis indicated that GABA shunt is operative in A. niger and its operation is enhanced during acidogenic growth of the fungus. This is the first report of an estimation of the flux through GABA shunt in a fungus.

Aspergillus niger↗
PubMed2000

A discussion of anti-Aspergillus niger glucose oxidase monoclonal antibody reactivity to red blood cells of several species.

We observed that mouse spleen cells from rosettes with autologous red blood cells (RBCs) and that rosette-formation was suppressed by anti-Aspergillus niger glucose oxidase monoclonal antibody (mAb). In the present study, we investigated whether RBCs of species besides mice have the structure recognized by anti-A. niger glucose oxidase mAb by using rosette-formation and complement-mediated hemolysis. Lysates of monkey and human RBCs did not suppress rosette-formation whereas autologous (mouse), rat and sheep RBC lysates partially suppressed rosette-formation. Those lysates exerted their suppressive activity after they had been treated at 56 degrees C for 30 min. A. niger glucose oxidase also suppressed rosette-formation with or without treatment at 56 degrees C for 30 min. Alternatively, anti-A. niger glucose oxidase mAb lysed mouse, rat and sheep RBCs but not human RBCs with complement. These findings suggest that the cell surfaces of mouse, rat and sheep RBCs have a structure which can be recognized by anti-A. niger glucose oxidase mAb while the cell surfaces of monkey and human RBCs do not.

Animals↗
PubMed2001

[Cloning and expression of Aspergillus niger glucose oxidase gene in methylotrophic yeast].

The DNA fragment encoding A. niger glucose oxidase was amplified by PCR using A. niger genomic DNA as template, and was cloned into vector of pPIC9 for expression in Pichia pastoris. When transformed into methylotrophic yeast Pichia pastoris GS115, The constructed plasmid pPICGOD1 directed the synthesis and secretion of functionally active GOD. After induction in MM medium for 4 days, the GOD activity in the medium reached 30-40 u/mL. SDS-PAGE revealed that recombinant yeast GOD was expressed up to 60%-70% of the total soluble protein, and the secreted GOD could be purified to electrophoretic homogeneity with one purification step using Q Sepharose Fast Flow ion exchange chromatography. The recombinant yeast GOD had very high catalytic activity, showed about 1.6-fold increase of specific activity over the commercial A. niger GOD. Kinetic analysis clearly demonstrated that recombinant yeast GOD showed similar substrate affinity for glucose to A. niger GOD, but the turnover number of the GOD from yeast was determined to be much higher than that of A. niger GOD. In addition, the linear range of glucose electrode made with recombinant yeast GOD was efficiently widened due to the high catalytic activity of yeast GOD.

Aspergillus niger↗
PubMed2006

[Glucoamylase enhancement regulated by blue light in Aspergillus niger].

Regulation of glucoamylase production in photoinduced A. niger under blue light were investigated. The results showed that continuous illumination of blue light was effective in promotion of conidiation, leading to more glucoamylase production due to the need of sporulation in A. niger. It was clear that 36h-old mycelium grown in dark was in the developmental stage of formation of conidiophore stalk and was most sensitive to BL A. niger cultures exhibited some competence stage to respond to blue light over a period of 36 h when early conidiophore stalk formed in darkness, and photoinduction at this critical period resulted in relatively higher yield of glucoamylase. The fluence-response data generated with blue light indicated that the optimum fluence required for the photomorphogenetic response in A. niger was no less than 450 (mol/m2 x s) to saturate the photoinduction system. The amount of glucoamylase gene (G1) transcripts accumulated during illumination with blue light was more than that in total darkness, whereas the threshold for G1 induction during illumination with increased gradient light was higher than that exposed directly to light of constant fluence, indicating the existence of a light adaptation mechanism for glucoamyalse production in response to blue light. Nevertheless, both high and low light were able to promote glucoamylase producing. Furthermore, suppression subtractive hybridization experiment revealed that some respiratory chain redox enzymes in mitochondria including alternative oxidase as well as sulfhydryl oxidase participated the photoresponse in A. niger and consequently influenced the metabolism. The results support a possibility of designing strategies to improve glucoamylase yield by application of blue light.

Aspergillus niger↗