Abstract
Streptomyces sp. TD-1 was identified as Streptomyces alboflavus based on its morphological characteristics, physiological properties, and 16S rDNA gene sequence analysis. The antifungal ...activity of the volatile-producing S. alboflavus TD-1 was investigated. Results showed that volatiles generated by S. alboflavus TD-1 inhibited storage fungi Fusarium moniliforme Sheldon, Aspergillus flavus, Aspergillus ochraceus, Aspergillus niger, and Penicillum citrinum in vitro. GC/MS analysis revealed that 27 kinds of volatile organic compounds were identified from the volatiles of S. alboflavus TD-1 mycelia, among which the most abundant compound was 2-methylisoborneol. Dimethyl disulfide was proved to have antifungal activity against F. moniliforme by fumigation in vitro.
Feruloyl esterase (FAE)-encoding genes
AnfaeA
and
AnfaeB
were isolated from
Aspergillus niger
0913. For overexpression of the two genes in
Trichoderma reesei
, constitutive and inductive expression ...plasmids were constructed based on parental plasmid pAg1-H3. The constructed plasmids contained
AnfaeA
or
AnfaeB
gene under the control of glyceraldehyde-3-phosphate dehydrogenase A gene (
gpd
A) promoter (from
A. nidulans
) or cellobiohydrolases I (
cbh
I) gene promoter (from
T. reesei
), and
cbh
I terminator from
T. reesei
. The target plasmids were transferred into
T. reesei
D-86271 (Rut-C30) by
Agrobacterium tumefaciens-
mediated transformation (ATMT), respectively. A high level of feruloyl esterase was produced by the recombinant fungal strains under solid-state fermentation, and the
cbh
I promoter was more efficient than the
gpd
A promoter in the expression of
AnfaeA
. The optimum temperatures and pH values were 50 °C and 5.0 for AnFAEA, and 35 °C and 6.0 for AnFAEB. The maximum production levels were 20.69 U/gsd for AnFAEA and 15.08 U/gsd for AnFAEB. The recombinant fungal enzyme systems could release 62.9% (for AnFAEA) and 52.2% (for AnFAEB) of total ferulic acids from de-starched wheat bran, which was higher than the 46.3% releasing efficiency of
A. niger
0913. The supplement of xylanase from
T. longibrachiatum
in the enzymatic hydrolysis led to a small increment of the ferulic acids release.
AmyR is commonly considered a regulator of starch degradation whose activity is induced by the presence of maltose, the disaccharide building block of starch. In this study, we demonstrate that the ...role of AmyR extends beyond starch degradation. Enzyme activity assays, genes expression analysis and growth profiling on
d
-glucose- and
d
-galactose-containing oligo- and polysaccharides showed that AmyR regulates the expression of some of the
Aspergillus niger
genes encoding α- and β-glucosidases, α- and β- galactosidases, as well as genes encoding α-amlyases and glucoamylases. In addition, we provide evidence that
d
-glucose or a metabolic product thereof may be the inducer of the AmyR system in
A. niger
and not maltose, as is commonly assumed.
In the tricarboxylic acid (TCA) cycle, NADP
+
-specific isocitrate dehydrogenase (NADP
+
-ICDH) catalyzes oxidative decarboxylation of isocitric acid to form α-ketoglutaric acid with NADP
+
as a ...cofactor. We constructed an NADP
+
-ICDH gene (icdA)-overexpressing strain (OPI-1) using Aspergillus niger WU-2223L as a host and examined the effects of increase in NADP
+
-ICDH activity on citric acid production. Under citric acid-producing conditions with glucose as the carbon source, the amounts of citric acid produced and glucose consumed by OPI-1 for the 12-d cultivation period decreased by 18.7 and 10.5%, respectively, compared with those by WU-2223L. These results indicate that the amount of citric acid produced by A. niger can be altered with the NADP
+
-ICDH activity. Therefore, NADP
+
-ICDH is an important regulator of citric acid production in the TCA cycle of A. niger. Thus, we propose that the icdA gene is a potentially valuable tool for modulating citric acid production by metabolic engineering.
We revealed that NADP
+
-specific isocitrate dehydrogenase (NADP
+
-ICDH) is an important regulator of citric acid production in Aspergillus niger by constructing NADP
+
-ICDH gene (icdA)-overexpressing strain (OPI-1) using strain WU-2223L as a host.
Grape and wine production in South America represents about 6.6% and 10% respectively of the world grape and wine production. The available information on the ochratoxigenic mycoflora and ochratoxin ...A (OTA) presence in wine grapes, wines, grape juices and dried vine fruits is limited. Surveys have been carried out in Argentina and Brazil which showed that
Aspergillus niger aggregate are predominant in the Argentinean varieties while from the Brazilian varieties the species
A. niger,
Aspergillus ochraceus and
Aspergillus carbonarius were isolated. A mycobiota survey from wine grapes in Argentina showed that while
Alternaria alternata was predominant,
Aspergillus section
Nigri species were isolated from 60% of samples. About 41% of black Aspergilli isolates produced OTA with levels ranging from 2 to 24.5 ng mL
−
1
. In another study, about 83% of
A. carbonarius isolates from dried vine fruits produced OTA, with levels ranging from 2 to 5200 ng mL
−
1
. A survey of grape juices and wines of Brazilian, Argentinean and Chilean origin were found to contain very low levels of OTA. Studies are in progress in Latin America on the ecophysiology of ochratoxigenic fungi and OTA occurrence to reduce the impact of this toxin in the food chain.
•Tet-on system in Aspergillus terreus developed.•pgnA, a nonribosomal peptide synthetase like gene identified and characterized in A. terreus.•Overexpression of pgnA led to the production of the ...secondary metabolite, phenguignardic acid.
Genome sequencing of the fungus Aspergillus terreus uncovered a number of silent core structural biosynthetic genes encoding enzymes presumed to be involved in the production of cryptic secondary metabolites. There are five nonribosomal peptide synthetase (NRPS)-like genes with the predicted A-T-TE domain architecture within the A. terreus genome. Among the five genes, only the product of pgnA remains unknown. The Tet-on system is an inducible, tunable and metabolism-independent expression system originally developed for Aspergillus niger. Here we report the adoption of the Tet-on system as an effective gene activation tool in A. terreus. Application of this system in A. terreus allowed us to uncover the product of the cryptic NRPS-like gene, pgnA. Furthermore expression of pgnA in the heterologous Aspergillus nidulans host suggested that the pgnA gene alone is necessary for phenguignardic acid (1) biosynthesis.
Bacterial-fungal interactions influence microbial community performance of most ecosystems and elicit specific microbial behaviours, including stimulating specialised metabolite production. Here, we ...use a co-culture experimental evolution approach to investigate bacterial adaptation to the presence of a fungus, using a simple model of bacterial-fungal interactions encompassing the bacterium Bacillus subtilis and the fungus Aspergillus niger. We find in one evolving population that B. subtilis was selected for enhanced production of the lipopeptide surfactin and accelerated surface spreading ability, leading to inhibition of fungal expansion and acidification of the environment. These phenotypes were explained by specific mutations in the DegS-DegU two-component system. In the presence of surfactin, fungal hyphae exhibited bulging cells with delocalised secretory vesicles possibly provoking an RlmA-dependent cell wall stress. Thus, our results indicate that the presence of the fungus selects for increased surfactin production, which inhibits fungal growth and facilitates the competitive success of the bacterium.
Many different organic compounds may be converted by microbial biotransformation to high-value products for the chemical and pharmaceutical industries. This review summarizes the use of strains of ...Aspergillus niger, a well-known filamentous fungus used in numerous biotechnological processes, for biochemical transformations of organic compounds. The substrates transformed include monocyclic, bicyclic, and polycyclic aromatic hydrocarbons; azaarenes, epoxides, chlorinated hydrocarbons, and other aliphatic and aromatic compounds. The types of reactions performed by A. niger, although not unique to this species, are extremely diverse. They include hydroxylation, oxidation of various functional groups, reduction of double bonds, demethylation, sulfation, epoxide hydrolysis, dechlorination, ring cleavage, and conjugation. Some of the products may be useful as new investigational drugs or chemical intermediates.
The genome of the white rot fungus Pycnoporus cinnabarinus includes a large number of genes encoding enzymes implicated in lignin degradation. Among these, three genes are predicted to encode glyoxal ...oxidase, an enzyme previously isolated from Phanerochaete chrysosporium The glyoxal oxidase of P. chrysosporium is physiologically coupled to lignin-oxidizing peroxidases via generation of extracellular H2O2 and utilizes an array of aldehydes and α-hydroxycarbonyls as the substrates. Two of the predicted glyoxal oxidases of P. cinnabarinus, GLOX1 (PciGLOX1) and GLOX2 (PciGLOX2), were heterologously produced in Aspergillus niger strain D15#26 (pyrG negative) and purified using immobilized metal ion affinity chromatography, yielding 59 and 5 mg of protein for PciGLOX1 and PciGLOX2, respectively. Both proteins were approximately 60 kDa in size and N-glycosylated. The optimum temperature for the activity of these enzymes was 50°C, and the optimum pH was 6. The enzymes retained most of their activity after incubation at 50°C for 4 h. The highest relative activity and the highest catalytic efficiency of both enzymes occurred with glyoxylic acid as the substrate. The two P. cinnabarinus enzymes generally exhibited similar substrate preferences, but PciGLOX2 showed a broader substrate specificity and was significantly more active on 3-phenylpropionaldehyde.
This study addresses the poorly understood role of how fungal peroxidases obtain an in situ supply of hydrogen peroxide to enable them to oxidize a variety of organic and inorganic compounds. This cooperative activity is intrinsic in the living organism to control the amount of toxic H2O2 in its environment, thus providing a feed-on-demand scenario, and can be used biotechnologically to supply a cheap source of peroxide for the peroxidase reaction. The secretion of multiple glyoxal oxidases by filamentous fungi as part of a lignocellulolytic mechanism suggests a controlled system, especially as these enzymes utilize fungal metabolites as the substrates. Two glyoxal oxidases have been isolated and characterized to date, and the differentiation of the substrate specificity of the two enzymes produced by Pycnoporus cinnabarinus illustrates the alternative mechanisms existing in a single fungus, together with the utilization of these enzymes to prepare platform chemicals for industry.
Commercial plant essential oils obtained from 11 Myrtaceae plant species were tested for their fumigant antifungal activity against Aspergillus ochraceus, A. flavus, and A. niger. Essential oils ...extracted from Leptospermum petersonii at air concentrations of 56 × 10(-3) mg/mL and 28 × 10(-3) mg/mL completely inhibited the growth of the three Aspergillus species. However, at an air concentration of 14 × 10(-3) mg/mL, inhibition rates of L. petersonii essential oils were reduced to 20.2% and 18.8% in the case of A. flavus and A. niger, respectively. The other Myrtaceae essential oils (56 × 10(-3) mg/mL) only weakly inhibited the fungi or had no detectable affect. Gas chromatography-mass spectrometry analysis identified 16 compounds in L. petersonii essential oil. The antifungal activity of the identified compounds was tested individually by using standard or synthesized compounds. Of these, neral and geranial inhibited growth by 100%, at an air concentration of 56 × 10(-3) mg/mL, whereas the activity of citronellol was somewhat lover (80%). The other compounds exhibited only moderate or weak antifungal activity. The antifungal activities of blends of constituents identified in L. petersonii oil indicated that neral and geranial were the major contributors to the fumigant and antifungal activities.
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