Soil receiving discharges from Pb-acid batteries dismantling and restoring units (PBS) can have a high concentration of phytoavailable Pb. Reducing Pb phytoavailability in PBS can decline Pb uptake in food crops and minimize the risks to humans and the environment. This pot study aimed to reduce the concentration of phytoavailable Pb in PBS through Aspergillus niger (A. niger)−mediated release of PO₄³⁻ from fish bone [Apatite II (APII)] products. The PBS (Pb = 639 mg kg⁻¹ soil) was amended with APII powder (APII−P), APII char (APII−C), and A. niger inoculum as separate doses, and combining A. niger with APII−P (APII−P + A. niger) and APII−C (APII−C + A. niger). The effects of these treatments on reducing the phytoavailability of Pb in PBS and its uptake in fenugreek were examined. Additionally, enzymatic activities and microbial biomass carbon (MBC) in the PBS and the indices of plant physiology, nutrition, and antioxidant defense machinery were scoped. Results revealed that the APII−C + A. niger treatment was the most efficient one. Compared to the control, it significantly reduced the Pb phytoavailability (DTPA-extractable Pb fraction) in soil and its uptake in plant shoots, roots, and grain, up to 61%, 83%, 74%, and 92%. The grain produced under APII−C + A. niger were safe for human consumption as Pb concentration in grain was 4.01 mg kg⁻¹ DW, remaining within the permissible limit set by WHO/FAO (2007). The APII−C + A. niger treatment also improved soil pH, EC, CEC, MBC, available P content and enzymatic activities, and the fenugreek quality parameters. A. niger played a significant role in solubilizing PO₄³⁻ from APII−C, which reacted with Pb and formed insoluble Pb-phosphates, thereby reducing Pb phytoavailability in PBS and its uptake in plants. This study suggests APII−C + A. niger can remediate Pb-polluted soils via reducing Pb phytoavailability in them.

Presence of microorganisms in soils strongly affects mobility of metals. This fact is often excluded when mobile metal fraction in soil is studied using extraction procedures. Thus, the first objective of this paper was to evaluate strain Aspergillus niger’s exometabolites contribution on aluminium mobilization. Fungal exudates collected in various time intervals during cultivation were analyzed and used for two-step bio-assisted extraction of alumina and gibbsite. Oxalic, citric and gluconic acids were identified in collected culture media with concentrations up to 68.4, 2.0 and 16.5 mmol L−1, respectively. These exometabolites proved to be the most efficient agents in mobile aluminium fraction extraction with aluminium extraction efficiency reaching almost 2.2%. However, fungal cultivation is time demanding process. Therefore, the second objective was to simplify acquisition of equally efficient extracting agent by chemically mimicking composition of main organic acid components of fungal exudates. This was successfully achieved with organic acids mixture prepared according to medium composition collected on the 12th day of Aspergillus niger cultivation. This mixture extracted similar amounts of aluminium from alumina compared to culture medium. The aluminium extraction efficiency from gibbsite by organic acids mixture was lesser than 0.09% which is most likely because of more rigid mineral structure of gibbsite compared to alumina. The prepared organic acid mixture was then successfully applied for aluminium extraction from soil samples and compared to standard single step extraction techniques. This showed there is at least 2.9 times higher content of mobile aluminium fraction in soils than it was previously considered, if contribution of microbial metabolites is considered in extraction procedures. Thus, our contribution highlights the significance of fungal metabolites in aluminium extraction from environmental samples, but it also simplifies the extraction procedure inspired by bio-assisted extraction of aluminium by common soil fungus A. niger.

Fungi are well associated with the degradation of hydrocarbons by the production of different enzymes, among which catalases (CBH), laccases (LCC) and peroxidases (LiP and MnP) are of immense importance. In this study, crude oil tolerance and enzyme secretions were demonstrated by rhizospheric fungal strains. Four most abundant strains were isolated from the rhizosphere of grasses growing in aged oil spill sites and identified through morphological characterization and molecular PCR-amplification of 5.8–28S ribosomal rRNA using ITS1 and ITS4 primers. These strains were subjected to crude oil tolerance test at 0–20% concentrations. Presence and transcriptase responses of putative genes lig (1–6), mnp, cbh (1.1, 1.1 and 11), and lcc encoding lignin peroxidase, manganese peroxidase, catalase, and laccase enzymes respectively were also studied in these strains using RT-PCR. In addition, activities of secreted enzymes by each strain were studied in aliquots. The strains were identified as Aspergillus niger asemoA (KY473958), Talaromyces purpurogenus asemoF (KY488463), Trichoderma harzianum asemoJ (KY488466), and Aspergillus flavus asemoM (KY488467) through sequencing and comparing the sequences’ data at NCBI BLAST search software. All the isolated strains showed tolerance to crude oil at 20% concentration, but the growth rate reduced with increasing in oil concentrations. All the isolated strains possess the tested genes and lig 1–6 gene was overexpressed in A. niger and T. harzianum while lcc and mnp genes were moderately expressed in all the four strains. Almost 145 U.mL⁻¹ of lignin and manganese peroxidase, 87 U.mL⁻¹ of catalase, and 180 U.mL⁻¹ of laccase enzymes were produced by these strains and it was also observed that these strain mostly produced studied enzymes in response to increasing crude oil concentrations. Considering the robust nature and diverse production of these catalytic enzymes by these strains, they can be exploited for various bioremediation technologies as well as other biotechnological applications.

The aim of this study was to evaluate bacterial and fungal aerosol concentrations at the holy mosque (Al-Masjid Al-Haram). Air samples were collected from different locations inside and outside the holy mosque, during the month of Ramadan-2011 (the fasting month), using a portable Air-port MD8 gelatin filter sampler. Trypticase soya agar and Capek's dox agar media were used to count bacteria and fungi, respectively. The mean concentrations of airborne bacteria and fungi ranged between 105–106 colony forming unit per cubic meter of air (CFU/m3) outside, and ∼102–105 CFU/m3 inside locations. The highest outside bacterial concentrations 106 CFU/m3 were found at the Al Umra, Al Fatah and eastern plazas, and the highest inside fungal concentrations ∼105 CFU/m3 were found at the courtyard, expansion of 1st floor, and roof. Significant differences (P < 0.05) were found between bacterial and fungal concentrations inside and outside sampling locations, higher concentrations shifted towards to outside locations. Significant differences were also found between the bacterial and fungal concentrations inside–unclosed and semi-closed (P < 0.05) with inside-closed locations. Gram-positive bacteria, Bacillus and Micrococcus, and fungi, Aspergillus niger were the dominant microbial aerosol genera. The obtained data is considered a step to make up the gap about airborne microbial contamination inside the holy mosque, and microbial air quality should be studied along over the year at the holy mosque in the future.

The genotoxicity of biogenic silver nanoparticles (AgNPs) obtained from three microbial mediators was assessed using the Allium cepa assay. Three clusters were differentiated for the highest frequency of end points of clastogenicity (stick-ends, fragments and bridges), end points of missegregation (C-metaphases and disorder anaphases), and lowest frequency of all the end points. In these clusters, the treatments were grouped respectively as I) positive control (GSF); II) silver nanoparticles form Aspergillus niger (AgNPs-An); and III) silver nanoparticles from both Cryptococcus laurentii (AgNPs-Cl) and Rhodotorula glutinis (AgNPs-Rg), Ag + , and negative control (NC). These results were in according to the principal component analisys (PCA) where treatments were associated to each component of the genotoxic effects. The statistical comparative analysis of the mitotic index (IM) and the abnormal mitosis frequency (AM) indicated that both GSF and AgNPsAn induce significant genotoxic effect. Low genotoxic effects were attributed to AgNPs-Cl and AgNPs-Rg, but mitogenic stimuli, similar to that obtained by the silver ions Ag + , were observed. Results suggested that different features of biogenic nanoparticles such as composition, size, and coating may be involved in the different cytological responses of the meristematic cells.

Pure NiO and NiO thin films doped with 0.1 to 25% Cu were grown on pre-heated soda-lime glass substrates via spray pyrolysis technique. The surface roughness of the NiO:Cu thin films decreased as Cu/Ni ratio was increased. Antifungal activity of these thin films against Aspergillus niger (A. niger) which affects some of the fruits, and Macrophomina phaseolina (M. phaseolina) which is a soil borne fungus responsible for the infection of root and lower stem of several plants, was then investigated by bioassay and broth dilution methods. The antifungal response of pure NiO thin film was weak but it improved considerably on doping with copper. The higher the copper content in NiO:Cu thin film, the better was its antifungal response. Moreover, for the given Cu/Ni ratio range of 0–25%, the optical density (OD) of Potato Dextrose (PD) broth inoculated with A. niger and containing NiO:Cu material was reduced or antifungal ability was enhanced by 8.3, 9.9, 11.7, and 13.4 times for the exposure time of 6, 8, 10, and 12 days, respectively. Similarly, the OD of PD broth inoculated with M. phaseolina and containing NiO:Cu material was reduced or antifungal ability was enhanced by 16–37 times in the exposure temperature range of 20–40 °C. A linear relationship of OD with crystallite size and lattice strain of the thin films showed that NiO:Cu material possessed memory of the structural modifications induced by the dopant atoms though its phase changed from crystalline to non-crystalline state. These results can be utilized in agricultural sector. Graphical abstract

Developing countries are increasingly concerned with pollution due to toxic heavy metals in the environment. Unlike most organic pollutants which can be destroyed, toxic metal ions released into the environment often persist indefinitely circulating and eventually accumulating throughout the food chain thus posing a serious threat to mankind. The use of biological materials for heavy metal removal or recovery has gained importance in recent years due to their good performance and low cost. Among the various sources, both live and inactivated biomass of organisms exhibits interesting metal binding capacities. Their complex cell walls contain high content of functional groups like amino, amide, hydroxyl, carboxyl, and phosphate which have been implicated in metals binding. In the present study, Aspergillus niger was used to analyze the metal uptake from an aqueous solution. The determination of Cu+2, Pb+2, Cd+2, Zn+2, Co-2 and Ni+2 in samples was carried out by differential Pulse Anodic Voltammetry (DPASV) and the Voltammograms. Production of oxalic acid was carried out by submerged fermentation. The organism used in the present study has the ideal properties to sequester toxic metals and grow faster.

This study aimed to evaluate possible synergistic interactions on antimicrobial and antioxidant efficacy of clove and cinnamon oil components in combination and characterization of compounds responsible for synergistic interactions using TLC bioautography followed by checkerboard titration, isobologram analysis, and spectrometric characterization. Among the combinations tested, cinnamaldehyde from cinnamon oil and eugenol from clove oil in combination showed a synergistic antimicrobial interaction against foodborne microbes Listeria monocytogenes (fractional inhibitory concentration index (FICI): 0.31), Salmonella typhimurium (FICI: 0.41), and Aspergillus niger (FICI: 0.48), and synergistic antioxidant efficacy (combination index: 0.78) in in vitro model. Cinnamaldehyde/eugenol blend did not show any cytotoxic effect (IC₅₀ > 1000 μg/ml) in human normal keratinocyte cell line. The results provide evidence that the cinnamaldehyde/eugenol blend may help in designing a more potent novel natural antimicrobial and antioxidant agent in food and pharmaceutical industries.

In degradation of total petroleum hydrocarbon, 35 isolates belonging to 11 genera were sanitized and 3 isolates as well as their consortium were initiated to be able to raise in association with petroleum hydrocarbon as sole source of carbon under in vitro circumstances. The isolated strains were grounded on internal transcribed spacer (ITS) rDNA sequence analysis. The fungal strains with the utmost potentiality to reduce petroleum hydrocarbon without emerging antagonistic activities were Aspergillus niger, Penicillium ochrochloron, and Trichodema viride. For fungal growth on petroleum hydrocarbon, P. ochrocholon gained weight of 44%, A. niger 49%, and T. viride 39% within the first 30–40 days. As compared to the controls, these fungi accumulated significantly higher biomass, produced extracellular enzymes, and degraded total petroleum hydrocarbon and A. niger strongly degraded total petroleum hydrocarbon with a degradation of about 71.19%. These observations with GC-MS data confirm that these isolates displayed rapid total petroleum hydrocarbon biodegradation within a period of 60 days and the half-life showed that A. niger was the shortest with t1/2 = 21.280 day⁻¹ corresponding to the highest percent degradation of 71.19% and first-order kinetic fitted into the present study. By multivariate analysis, five main factors were identified by factor analysis (FA). The first factor (F1) of the fungi species accounts for 20.0% which signifies that fungi species controls the degradation of petroleum variability and hierarchical cluster analysis (HCA) as a dendrogram with five observations and three variables shows two predominant clusters order cluster 1 > 2.

This study aimed to determine the mycoremediative capacity of filamentous fungi consortia in landfill heavy metal contaminated soil. Streak plate method was utilized for the isolation of fungi from the landfill soil. Isolates were identified using morphological and molecular techniques. Heavy metal tolerance of the fungi was determined using radial growth diameter technique. Twelve species of landfill indigenous fungi were used for the bioremediation process. Two categories of fungi consortia namely highly tolerant fungi (Perenniporia subtephropora, Daldinia starbaeckii, Phanerochaete concrescens, Cerrena aurantiopora, Fusarium equiseti, Polyporales sp., Aspergillus niger, Aspergillus fumigatus, and Trametes versicolor) and moderately tolerant fungi (Paecilomyces lilacinus, Antrodia serialis, and Penicillium cataractum) were used to amend the contaminated soil; meanwhile, the unamended soil served as control. Maximum tolerance index of 1.0 was reported in Cr-, Cu-, and Fe-amended PDA medium. Meanwhile, the maximum heavy metal bioremoval efficiencies were for highly tolerant fungal consortium treated soil and were recorded as As (62%) > Mn (59%) > Cu (49%) > Cr (42%) > Fe (38%). Likewise, the maximum metal removal rate constant (K) and the half-lives (t₁/₂) were 0.0097/day 71 days, 0.0088/day 79 days, 0.0067/day 103 days, 0.0054/day 128 days, and 0.0048/day 144 days for As, Mn, Cu, Cr, and Fe, respectively, which were all for soil treated with consortium of highly tolerant fungi (P. subtephropora, D. starbaeckii, P. concrescens, C. aurantiopora, F. equiseti, Polyporales sp., A. niger, A. fumigatus, and T. versicolor). Spectra analysis revealed a clear distinction in the functional groups between the fungal treated and the untreated soils. Peaks at 874 ± 2 cm⁻¹ and 1425 ± 2 cm⁻¹ were only found in fungi amended soil. Physicochemical parameters mainly pH and redox potential played a key role in the bioremediation process, and bioaccumulation was believed to be the favored mechanism for the metal bioremoval. The data are suitable for assessing the contribution of bioaugmentation with consortia of fungi. It is equally important for assessing the synergistic effect of fungi on the reduction of extractable heavy metals in contaminated soil.