Fungus Aspergillus Niger Research Articles

Evaluation of the effectiveness of RNA silencing in the filamentous fungus Aspergillus niger using a binary vector integrated with Gateway recombination cloning technology

The filamentous fungus Aspergillus niger is widely employed in the production of citric acid and some industrial enzymes such as phytase, glucoamylase, and glucose oxidase. Currently, several genetic modification tools have been developed and applied to this fungal species. However, the RNA silencing technique is less used for A. niger. In the present study, an RNA silencing binary vector integrated with the Gateway recombination cloning technology was evaluated in A. niger. The integration of Gateway recombination cloning technology in binary vectors for rapid generation of hairpin RNA structure allowed the assessment of inhibition of target gene expression through mRNA degradation. The RNA silencing constructs were successfully transferred into A. nigervia Agrobacterium tumefaciens. Results showed that the RNA silencing vectors were effective in downregulating the expression of the DsRed fluorescent reporter gene and the stuA regulatory gene. Interestingly, the silenced mutants of stuA exhibited a significant reduction in fungal sporulation. This finding revealed that the RNA silencing technique with the examined Gateway binary vector represents a potential genetic tool for functional studies of target genes in A. niger.

Assessment of the Fungistatic Properties of Calendula officinalis L. Water Extract and the Effect of Its Addition on the Quality of Wheat Bread

The potential of Calendula officinalis water extract against fungi Aspergillus niger and Penicillium sp. and the effect of extract addition on the quality of wheat bread were investigated. In vitro, the extract reduced the mycelial growth and biomass production of A. niger, but there was no inhibitory effect on Penicillium sp. Enriched bread showed significantly higher total phenolic content, by about 77% and 95% in the bread, in which 10% and 15% of the water was replaced with extract, respectively. The antioxidant potential against DPPH• was significantly higher (compared to the control) in both variants used in the experiment, and the level of antioxidant activity increased with the addition of extract. The enriched bread had good quality characteristics—lower baking losses and higher volume than the control. The moisture content and acidity of the crumb of the extract-enriched bread were also higher. The extract additive used did not affect the sensory properties of the bread.

Aspergillus niger confers health benefits and modulates the gut microbiota of juvenile Pacific white shrimp (Penaeus vannamei) under farming conditions

IntroductionThe fungus Aspergillus niger is found to be predominant in the body of Pacific white shrimp (Penaeus vannamei); however, its role in shrimp’s health has not been explored. This study aimed to evaluate the influences of A. niger on growth, antioxidative activity, immune response, and gut microbiota of juvenile Pacific white shrimps under farming conditions.MethodsShrimps (2.30±1.05 g) were fed diets supplemented with 0 (control), 1.5 (A1.5), or 3.0 g/kg diet of A. niger (A3.0) for one month. At the end of the study, the growth, antioxidant enzyme activity and immune parameters, and gut microbiota in shrimps fed with different experimental diets were analyzed.ResultsThe results showed a significant increase in weight gain, specific growth rate, and length gain of shrimps in A1.5, compared with other groups (P<0.05). With the exception of lysozyme in both A1.5 and A3.0, which were lower than in the control, the activity of superoxide dismutase (SOD), catalase, acid phosphatase, alkaline phosphatase, and phenol oxidase was higher than those in the control. Gene expressions of SOD, anti-lipopolysaccharide factor-ALF1, and ALF2 (in A1.5 and A3.0) and nitric oxide synthase, penaeidin-PEN2 (in A1.5) and PEN3 and PEN4 (in A3.0) were significantly up-regulated compared to the control (P<0.05). The addition of A. niger increased diversity and separated the microbial community in the gut of shrimps. At the phylum level, Firmicutes and Bacteroidota were dominant, and Proteobacteria was less abundant in the A1.5 and A3.0, as compared to the control. At the genus level, the relative abundance of Vibrio, Marivita, and Roseobacter was increased but Ruegeria was decreased in A1.5 and A3.0 when compared to the control. The genera Edwardsiella, Clostridium sensu stricto 1, and Shimia in the A1.5 were higher than in the control.DiscussionThese findings demonstrated the beneficial effects of A. niger on growth, health, and changes in the gut microbiota in shrimps under farming conditions. The recommended concentration of A. niger in the diet for shrimps is 1.5 g/kg diet.

Inhibitory Effect of Natural Honey on The Growth of Rhizopus stolonifer, Mucor spp., and Aspergillus niger

Background: Honey is frequently used as an antiseptic, prophylactic, and therapeutic agent for many infections. The chemical and physical properties of honey have an inhibitory effect on a lot of microorganisms including fungi. Rhizopus stolonifer, Mucor spp., and Aspergillus niger are common indoor molds that contaminate bread and eatable plants. During growth on bread, they multiply and produce large numbers of spores that can cause different types of infections, especially in immunocompromised patients. Objectives: 1) To evaluate the effect of natural honey on the growth of Rhizopus stolonifer, Mucor spp., and Aspergillus niger fungi. 2) To determine the minimal inhibitory concentration of honey that can suppress the growth of these fungi. 3) To assess the possibility of using honey as a natural replacement for chemical preservatives. Methodology: This experimental study was conducted in the College of Sciences at King Saud University between August and November 2021 in Riyadh, KSA. Multifloral honey was diluted in sterile distilled water volume to volume (%, v/v) in series concentrations: 5%, 15%, 30%, 45%, and 60%. The diluted samples of honey were then added to potato dextrose agar (PDA). Measured parts of the colonies of Rhizopus stolonifer, Mucor, and Aspergillus niger, were cultured on the PDA plates with the diluted honey. Two replicates were used for every concentration of each fungus. The inoculated plates, including the controls, were incubated at room temperature (25±2°C). Fungal growth was monitored daily for three months. Results: The 5%, 15%, and 35% concentrations of honey mixed with PDA did not inhibit the fungal growth, the fungi grew within the first 24h while the 60 % dilute concentration killed the three fungi and completely inhibited their growth. The fungi were monitored for 3 months; during that time, there was no growth. In conclusion: This study confirms that honey strongly inhibits the growth of Rhizopus Stolonifer, Mucor spp., and Aspergillus niger when used in a concentration of 60% or above. Accordingly based on these findings we determine that the minimal inhibitory concentration (MIC) of multi-floral honey on bread fungi is 60%.

Synthesis of Silver(I) Complexes Containing 3-Oxo-3-phenyl-2-(2-phenylhydrazono)propanal-Based Ligands as a Multifunction Platform for Antimicrobial and Optoelectronic Applications.

Toward multifunctionality, including antimicrobial and optoelectronic applications, herein, we reported the synthesis of a novel Ag(I) complex with 3-oxo-3-phenyl-2-(2-phenylhydrazono)propanal-based ligands including 3-(4-chlorophenyl)-2-[2-(4-nitrophenyl)hydrazono]-3-oxopropanal (named as "4A"), 3-(4-chlorophenyl)-2-[2-(4-methylphenyl)hydrazono]-3-oxopropanal (named as "6A"), and 3-(4-chlorophenyl)-3-oxo-2-(2-phenylhydrazono)propanal (named as "9A"). The synthesized compounds were characterized through FTIR, 1H NMR, and density functional theory (DFT). The morphological features and thermal stability were evaluated through transmission electron microscopy (TEM) and TG/DTA analysis. The antimicrobial activity of the synthesized Ag complexes was tested against various pathogens, including Gram-negative bacteria (Escherichia coli and Klebsiella pneumonia), Gram-positive bacteria (Staphylococcus aureus and Streptococcus mutans), and fungi (Candida albicans and Aspergillus niger). Results show that the synthesized complexes (Ag(4A), Ag(6A), and Ag(9A)) possess promising antimicrobial efficacy against various pathogens and are in good competition with several standard drugs as well. On the other hand, the optoelectronic features such as absorbance, band gap, and Urbach energy were examined by measuring the absorbance using a UV-vis spectrophotometer. The values of the band gap reflected the semiconducting nature of these complexes. The complexation with Ag resulted in a lowering band gap to match the apex of the solar spectrum. Such low band gap values are preferable for optoelectronic applications like dye-sensitized solar cells, photodiodes, and photocatalysis.

Production of Kojic Acid by Aspergillus niger M4 with Different Concentrations of Yeast Extract as a Nitrogen Source

In agro-industrial processes, microorganisms that are not pathogenic and that generate molecules are generally recognized as safe (GRAS). The Aspergillus niger fungus has different industrial applications, being used to produce citric acid and 166 other secondary metabolites. The objective of this research was to optimize a culture medium to induce the production of kojic acid (KA) by the Aspergillus niger M4 strain in a liquid fermentation process. Four fermentative kinetics were developed in flasks, using different levels of yeast extract in (1) 0.05 g/L, (2) 0.10 g/L, (3) 2.5 g/L, and (4) 2.5 g/L + Zinc sulfate. The culture medium conditions influenced the formation and speed of biomass and the synthesis and yield of KA. The optimum production points were from 72 h and 96 h with 0.552 g/L and 0.510 g/L of KA using 2.5 g/L of yeast extract and with a pH of 5.5. The Aspergillus niger M4 strain had the ability to produce kojic acid, which was induced by the concentration of the nitrogen source.

Investigation of some new main group metal complexes of hydrazine and 2‐mercaptopyridine‐3‐carboxylic acid mixed–ligands

AbstractSynthesis of some new coordination complexes of main group metals (Ba, Ca, Mg, Sr, and Pb) with 2‐mercaptopyridine‐3‐carboxylic acid (H2Mpc) and hydrazine mixed ligands and their characterization through various chemical and spectral analyses are described in this article. With the help of analytical data obtained from mass, elemental (CHNS), hydrazine content, and metal content analysis, the molecular formulae of the complexes have been proposed as [Ba(N2H4)2(HMpc)H2O], [Ca(N2H4)2(HMpc)(H2O)2], [Sr(N2H4)(HMpc)(H2O)3], [Mg(N2H4)4(HMpc)].4H2O and [Pb(N2H4)5(HMpc)2]. The vibrational (FT‐IR and Raman) spectral data exposes that the 2‐mercaptopyridine‐3‐carboxylic acid coordinates with metal ion via both carboxylate‐O and thiolate‐S in the mode of bi‐dentate dianion while the hydrazine acts as bridging bi‐dentate. On thermal decomposition, these complexes dehydrate to give metal 2‐mercaptopyridine‐3‐carboxylate intermediates, which on further decomposition (heating upto 750°C) give the metal carbonates in the cases of Ba, Ca and Sr, and metal oxides for Mg and Pb. The in vitro antibacterial and antifungal activity of the ligand and its complexes are studied against five bacteria (Bacillus cereus, Staphylococcus aureus, Proteus vulgaris, Pseudomonas aeruginosa and Escherichia coli) and four fungi (Candida albicans, Aspergillus niger, Aspergillus fumigatus, and Penicilium variance).

Morphology of Oil Palm (Elaeis guineensis Jacq.) Seedlings Under Drought Stress with Oil Palm Shell Ash and Aspergillus niger treatment

Climate change is a limiting factor that contributes to weather anomalies such as varying rainfall intensity. Weather abnormalities impact plantation crops, such as oil palm, which are very sensitive to water deficits, and inhibition of growth in the nursery phase reduces seed quality. In an effort to increase the resistance of oil palm seedlings to drought stress, palm shell ash is given because it contains high silicon (Si) ranging from 43% to 63%. Furthermore, the fungus Aspergillus niger is known to decompose and release insoluble silicon into orthosilicic acid into the soil solution, which can be absorbed by plants, This study used randomized block design with two factors drought stress factor with four level field capacity (FC) of 80%, 60%, 40% dan 20%; factor palm oil shell and Aspergillus niger 0, 10, 20, 30 g + 5 ml/polybag. The results showed that the parameter number of Aspergillus niger colonies before and after the drought stress treatment decreased, drought stress was also a significant difference in the parameters of plant height and number of leaves, while the treatment of oil palm shell ash with the addition of Aspergillus niger had no significant effect on plant height parameters and number of leaves of oil palm seedlings.

Isolation And Characterization Of Phosphate Solubilizing Fungi From Fruit And Vegetable Peel Waste Compost Fertilizer

Phosphate solubilizing fungi are fungi that can convert phosphate in soil from compound form (almost insoluble) into ionic form (easily soluble) so that it can be utilized by plants. The purpose of this study was to determine the isolation and characteristics of phosphate solubilizing fungi isolates found in fruit and vegetable peel waste compost. This research was conducted in January 2023 until completion in the Laboratory of the Faculty of Science and Technology, Labuhanbatu University. This research was carried out by isolating fungi from municipal waste compost, characterizing morphology and the ability to dissolve phosphate and molecular identification. Furthermore, the data were analyzed descriptively based on the research results obtained. There were 4 isolates of phosphate solubilizing fungi that were able to form clear zones on Pikovskaya media with different morphological characteristics and ability to dissolve phosphate. The largest clear zone diameter was shown in isolate A3 of 3 cm which is Aspergillus niger fungus.

Structural, microstructural, vibrational, and thermal investigations of NiO nanoparticles for biomedical applications

The structural, morphological, thermal, and anti-microbial properties of NiO nanoparticles were investigated using natural fuels in conjunction with the combustion process. XRD revealed the Face-centered cubic polycrystalline structure in all of the samples. The crystallite diameters for tea extract, wine, honey, and cow urine-assisted nanoparticles were 32.60 nm, 27.41 nm, 29.58 nm, and 27.75 nm, respectively, according to the WH plot for NiO nanoparticles. The FESEM and EDAX analytical results corroborate the stoichiometric of the products as well as the existence of diamond, pollen grain, cluster pore, and mushroom-like morphologies. The average particle size as assessed by TEM and the size of crystallites are connected. All XRD pattern parameters that were matched with JCPDS data (04–0835), as well as the FTIR spectrum, support the presence of a pure phase of Face-centered cubic NiO in the range of 453.57 cm-1 to 438 cm-1. Thermal investigations (TG-DTA) indicated that the particles were stable even at 1000 °C. When NiO is subjected to thermal analysis, there is evidence of weight gain and loss. Anti-microbial study of organically fueled NiO used Staphylococcus aureus (Gram-positive) and Pseudomonas aeruginosa (Gram-negative) bacteria, as well as Candida albicans and Aspergillus niger fungi. It has been discovered that NPs are more efficient at inhibiting fungal growth than bacterial development.

Fragmentation of Aspergillus niger pellets in stirred tank bioreactors due to hydrodynamic stress

Filamentous fungi are widely exploited as cell-factories in industry due to their metabolic diversity, high production capacity and secretion efficiency. In stirred tank bioreactors, the filamentous fungus Aspergillus niger builds agglomerates of complex morphology. The formed morphology has a decisive influence on productivity and is significantly influenced by the hydrodynamic stress induced by the stirrer. Due to the complex interactions between the cultivation parameters, an examination solely of the influence of the stirrer is difficult. In this work, fragmentation experiments were established and conducted allowing the selective examination of the impact of stirrer type and stirring intensity on the bio-agglomerates’ morphology at a reasonable effort. With the applied method, a clear order of stress intensity for different stirrer types was found. Studying the breakage mechanism, both fracture and abrasion have been found to occur, significantly depending on the employed stirrer type. The impeller swept volume model has been proven to correlate the particle size well for the employed stirrer types. In the literature, most work on the characterisation of stirrer types concerning hydrodynamic stress has been done using model systems. The extensive results obtained earlier at our department using a liquid/liquid model system agree with the results of this work.

Solid Fungi Starters Using Aspergillus spp. under Different Manufacturing Conditions

The generation of royalties on the use of foreign-made inoculum strains or starters as a result of the implementation of the ‘Nagoya Protocol’ has led to efforts and healthy competition to secure useful biological resources in each country. In this study, we recognized the necessity and importance of securing useful strains in Korea and produced starters using five strains of fungi (Aspergillus oryzae and Aspergillus niger). Specifically, the quality characteristics exhibited by different strain inoculum concentrations (1, 3, 5% (v/w)) and drying conditions (low-temperature air drying at 35 °C for 24 h and high-temperature hot air drying at 45 °C for 18 h) during the starter manufacturing process were analyzed. Parameters such as enzyme activity and free amino acid and volatile flavor compound content, which may vary based on production conditions, are expected to produce basic data for the production of Korean-type starters.

Bioscorodite Production from As(III) and Fe(II) Salts under Oxidizing and Acidic Conditions of Trichoderma atroviride Culture

Arsenic (As) contamination of groundwater is widespread and significantly affects drinking water, posing a threat to public health due to its classification as a human carcinogen. Arsenic (As) can be removed from contaminated water using sustainable technologies (e.g., biotechnological processes). The process of removing Arsenic from water through reactions with iron under acidic and oxidizing conditions in a fungal broth has been proposed alongside the production of bioscorodite (FeAsO4·2H2O) crystals by Trichoderma atroviride culture. This ascomycete was selected based on tests with three other fungi (Aspergillus niger, and the basidiomycetes, Postia placenta, and Phanerochaete chrysosporium) because it decreased the pH to 2.2, raised the redox potential (Eh) to 207 mV, and was the quickest to produce 0.39 µg/L of H2O2 in a modified Wunder medium. The Eh was further increased to 324.80 mV under improved fungal culture conditions, selected using a 23−1 fractional factorial design (FFD). The fungal broth was then used for bioscorodite production by adding Fe(III)/As(III) salts and scorodite seeds at 92 °C for 21 h. Scorodite seeds and bioscorodite were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Arsenic was determined in solution by atomic absorption spectrophotometry (AAS), and a 73% reduction in the initial As concentration (0.30 g/100 mL) was observed after bioscorodite production. Bioscorodite production under appropriate fungal culture conditions could be an option for sustainable As removal from water. The production of H2O2 by the fungus resulted in the oxidation of As(III) into As(V) and acidification of the culture broth, which created the necessary conditions for the production of bioscorodite without the need for chemical acids or oxidants. This approach is environmentally friendly and cost effective, making it a promising alternative for the treatment of arsenic-contaminated water.

Effects of H.uvarum combined with KGM on postharvest diseases of blueberry

The aim of this work was to evaluate the efficacy of an innovative edible coating that combines Hanseniaspora uvarum and konjac glucomannan to preserve blueberries. The antagonistic yeast and four main fungi (Aspergillus niger, Penicillium, Alternaria alterniformis, Pseudomonas spp.) isolated from blueberry pathogens were subjected to in vitro antibacterial experiments, and the optimal concentration of antagonistic yeast was determined as 1 × 108 CFU/mL. The antibacterial mechanism of yeast against pathogenic fungi was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, viscometry, measurement of electrospray droplet size and coating thickness. Finally, the resulting spray was used to treat blueberry wound rot and to store blueberries. After 14 days of storage, the konjac glucomannan/Hanseniaspora uvarum composite coating solution was found to be more effective in maintaining blueberry quality compared with the control and konjac glucomannan groups.

Efficacy of phytohormones producing isolates on the growth of two stem-cutting robusta coffee (Coffea canephora)

The propagation techniques of robusta coffee by cutting can be accelerated by the application of plant growth-promoting hormones. This study is to determine the efficacy of phytohormone-producing isolates on the growth of two-segment cutting of Robusta coffee. The study was conducted using a non-factorial completely randomized design with 2 replications. The treatments consist of control, synthetic IBA (Rooton-f) with three dilution concentrations, 4 isolates (Rhodococcus qingshengii, Burkholderia ambifaria, and Bacillus wiedmannii; fungi Aspergillus niger) with three dilution concentrations. Observed parameters included a percentage of live cuttings, percentage of cuttings sprouted, percentage of rooted cuttings, plant height, number of shoots, number of internodes, number of leaves, number of primary roots, primary root length, and primary root diameter. The results showed that the B. wiedmannii treatment had the best performance compared to other treatments because this isolate produced the highest number of primary roots (4.60) and primary root diameters (2.97 mm) compared to other treatments including control and Rooton-f. This is related to its ability to produce phytohormones that can stimulate the root growth of coffee robusta cuttings.

Metabolomic profiling and its association with the bio-efficacy of Aspergillus niger strain against Fusarium wilt of guava.

Bio-control agents are the best alternative to chemicals for the successful management of plant diseases. The fungus Aspergillus niger is known to produce diverse metabolites with antifungal activity, attracting researchers to exploit it as a bio-control agent for plant disease control. In the present study, 11 A. niger strains were isolated and screened for their antagonism against the guava wilt pathogen under in vitro and in planta conditions. Strains were identified morphologically and molecularly by sequencing the internal transcribed spacer (ITS), β-tubulin, and calmodulin genes. The strains were evaluated through dual culture, volatile, and non-volatile methods under an in vitro study. AN-11, AN-6, and AN-2 inhibited the test pathogen Fusarium oxysporum f. sp. psidii (FOP) at 67.16%, 64.01%, and 60.48%, respectively. An in planta study was conducted under greenhouse conditions with 6 months old air-layered guava plants (var. Allahabad Safeda) by pre- and post-inoculation of FOP. The AN-11 strain was found to be effective under both pre- and post-inoculation trials. Furthermore, gas chromatography-mass spectrometry (GC-MS) analysis was carried out to characterize the volatile compounds of the most potential strain, A. niger. The hexane soluble fraction showed the appearance of characteristic peaks of hexadecenoic acid methyl ester (4.41%), 10-octadecanoic acid methyl ester (3.79%), dodecane (3.21%), undecane (3.19%), gibepyrone A (0.15%), 3-methylundecane (0.36%), and citroflex A (0.38%). The ethyl acetate fraction of the bio-control fungi revealed the occurrence of major antifungal compounds, such as acetic acid ethyl ester (17.32%), benzopyron-4-ol (12.17%), 1,2,6-hexanetriol (7.16%), 2-propenoic acid ethanediyl ester (2.95%), 1-(3-ethyloxiranyl)-ethenone (0.98%), 6-acetyl-8-methoxy dimethyl chromene (0.96%), 4-hexyl-2,5-dihydro dioxo furan acetic acid (0.19%), and octadecanoic acid (1.11%). Furthermore, bio-control abilities could be due to hyper-parasitism, the production of secondary metabolites, and competition for sites and nutrients. Indeed, the results will enrich the existing knowledge of metabolomic information and support perspectives on the bio-control mechanism of A. niger.

GC-MS Based Characterization, Antibacterial, Antifungal and Anti-Oncogenic Activity of Ethyl Acetate Extract of Aspergillus niger Strain AK-6 Isolated from Rhizospheric Soil.

Rhizospheric soil is the richest niche of different microbes that produce biologically active metabolites. The current study investigated the antimicrobial, antifungal and anticancer activities of ethyl acetate extract of the potent rhizospheric fungus Aspergillus niger AK6 (AK-6). A total of six fungal isolates were isolated, and isolate AK-6 was selected based on primary screening. Further, it exhibited moderate antimicrobial activity against pathogens such as Klebsiella pneumonia, Candida albicans, Escherichia coli, Shigella flexneri, Bacillus subtilis and Staphylococcus aureus. The morphological and molecular characterization (18S rRNA) confirmed that the isolate AK-6 belonged to Aspergillus niger. Further, AK-6 showed potent antifungal activity with 47.2%, 59.4% and 64.1% of inhibition against Sclerotium rolfsii, Cercospora canescens and Fusarium sambucinum phytopathogens. FT-IR analysis displayed different biological functional groups. Consequently, the GC-MS analysis displayed bioactive compounds, namely, n-didehydrohexacarboxyl-2,4,5-trimethylpiperazine (23.82%), dibutyl phthalate (14.65%), e-5-heptadecanol (8.98%), and 2,4-ditert-butylphenol (8.60%), among the total of 15 compounds isolated. Further, the anticancer activity of AK-6 was exhibited against the MCF-7 cell line of human breast adenocarcinoma with an IC50 value of 102.01 μg/mL. Furthermore, flow cytometry depicted 17.3%, 26.43%, and 3.16% of early and late apoptosis and necrosis in the AK-6 extarct treated MCF-7 cell line, respectively. The results of the present analysis suggest that the isolated Aspergillus niger strain AK-6 extract has the potential to be explored as a promising antimicrobial, antifungal and anticancer drug for medical and agricultural applications.

Hybrid Silver-Containing Materials Based on Various Forms of Bacterial Cellulose: Synthesis, Structure, and Biological Activity.

Sustained interest in the use of renewable resources for the production of medical materials has stimulated research on bacterial cellulose (BC) and nanocomposites based on it. New Ag-containing nanocomposites were obtained by modifying various forms of BC with Ag nanoparticles prepared by metal-vapor synthesis (MVS). Bacterial cellulose was obtained in the form of films (BCF) and spherical BC beads (SBCB) by the Gluconacetobacter hansenii GH-1/2008 strain under static and dynamic conditions. The Ag nanoparticles synthesized in 2-propanol were incorporated into the polymer matrix using metal-containing organosol. MVS is based on the interaction of extremely reactive atomic metals formed by evaporation in vacuum at a pressure of 10-2 Pa with organic substances during their co-condensation on the cooled walls of a reaction vessel. The composition, structure, and electronic state of the metal in the materials were characterized by transmission and scanning electron microscopy (TEM, SEM), powder X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and X-ray photoelectron spectroscopy (XPS). Since antimicrobial activity is largely determined by the surface composition, much attention was paid to studying its properties by XPS, a surface-sensitive method, at a sampling depth about 10 nm. C 1s and O 1s spectra were analyzed self-consistently. XPS C 1s spectra of the original and Ag-containing celluloses showed an increase in the intensity of the C-C/C-H groups in the latter, which are associated with carbon shell surrounding metal in Ag nanoparticles (Ag NPs). The size effect observed in Ag 3d spectra evidenced on a large proportion of silver nanoparticles with a size of less than 3 nm in the near-surface region. Ag NPs in the BC films and spherical beads were mainly in the zerovalent state. BC-based nanocomposites with Ag nanoparticles exhibited antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli bacteria and Candida albicans and Aspergillus niger fungi. It was found that AgNPs/SBCB nanocomposites are more active than Ag NPs/BCF samples, especially against Candida albicans and Aspergillus niger fungi. These results increase the possibility of their medical application.

Sedril Formatın Mikrobiyal Dönüşümü

Cedryl formate is a synthetic fragrance compound, which is an ester derivative of the sesquiterpenoid cedrol, found in different parts of the cedar tree/cedarwood with a characteristic fragrance. Cedryl formate is used in cosmetics and personal care products like fragrances, perfumes, as well as in the chemical and agriculture industries in various forms. In the present work, the microbial transformation of the formate was evaluated by 13 fungal cultures to produce new derivatives. Among the evaluated, the plant pathogenic fungus Aspergillus niger NRRL 326, biotransformed to the metabolite 8-cedren-3β-ol derivative with 6.2% yield. The structure of the chromatographically purified metabolite was elucidated by NMR and spectroscopic methods.

A newly constructed Agrobacterium-mediated transformation system based on the hisB auxotrophic marker for genetic manipulation in Aspergillus niger.

The filamentous fungus Aspergillus niger is widely exploited as an industrial workhorse for producing enzymes and organic acids. So far, different genetic tools, including CRISPR/Cas9 genome editing strategies, have been developed for the engineering of A. niger. However, these tools usually require a suitable method for gene transfer into the fungal genome, like protoplast-mediated transformation (PMT) or Agrobacterium tumefaciens-mediated transformation (ATMT). Compared to PMT, ATMT is considered more advantageous because fungal spores can be used directly for genetic transformation instead of protoplasts. Although ATMT has been applied in many filamentous fungi, it remains less effective in A. niger. In the present study, we deleted the hisB gene and established an ATMT system for A. niger based on the histidine auxotrophic mechanism. Our results revealed that the ATMT system could achieve 300 transformants per 107 fungal spores under optimal transformation conditions. The ATMT efficiency in this work is 5 - 60 times higher than those of the previous ATMT studies in A. niger. The ATMT system was successfully applied to express the DsRed fluorescent protein-encoding gene from the Discosoma coral in A. niger. Furthermore, we showed that the ATMT system was efficient for gene targeting in A. niger. The deletion efficiency of the laeA regulatory gene using hisB as a selectable marker could reach 68 - 85% in A. niger strains. The ATMT system constructed in our work represents a promising genetic tool for heterologous expression and gene targeting in the industrially important fungus A. niger.