Biosorption has been considered a promising technology for the treatment of industrial effluents containing heavy metals. However, the development of a cost-effective technique for biomass ...immobilization is essential for successful application of biosorption in industrial processes. In this study, a new method of reversible encapsulation of the highly pigmented biomass from Aspergillus nidulans mutant using semipermeable cellulose membrane was developed and the efficiency of the encapsulated biosorbent in the removal and recovery of copper ions was evaluated. Data analysis showed that the pseudo-second-order model better described copper adsorption by encapsulated biosorbent and a good correlation (r2 > 0.96) to the Langmuir isotherm was obtained. The maximum biosorption capacities for the encapsulated biosorbents were higher (333.5 and 116.1 mg g-1 for EB10 and EB30, respectively) than that for free biomass (92.0 mg g-1). SEM-EDXS and FT-IR analysis revealed that several functional groups on fungal biomass were involved in copper adsorption through ion-exchange mechanism. Sorption/desorption experiments showed that the metal recovery efficiency by encapsulated biosorbent remained constant at approximately 70% during five biosorption/desorption cycles. Therefore, this study demonstrated that the new encapsulation method of the fungal biomass using a semipermeable cellulose membrane is efficient for heavy metal ion removal and recovery from aqueous solutions in multiple adsorption-desorption cycles. In addition, this reversible encapsulation method has great potential for application in the treatment of heavy metal contaminated industrial effluents due to its low cost, the possibility of recovering adsorbed ions and the reuse of biosorbent in consecutive biosorption/desorption cycles with high efficiency of metal removal and recovery.
In order to find a sustainable and low-cost alternative route to the traditional recovery of aluminum, the filamentous fungus
Penicillium simplicissimum
was evaluated for aluminum recovery from ...low-grade bauxite ore. The oat-agar medium was carefully chosen as the foremost solid medium for fungal sporulation due to lower cost, ease in preparation, and high spore production in a short incubation time. To examine the acid production capability in submerged fermentation,
P. simplicissimum
was inoculated in a medium augmented with glucose and molasses as an energy source. High-performance liquid chromatography (HPLC) technique was used for the determination of the produced organic acids. Three different bioleaching approaches were evaluated using 1% bauxite pulp density. The culture containing
P. simplicissimum
spores grown in a medium supplemented with molasses leached 86.6% Al in the direct two steps on the fifth day, 56.5% in the direct one step on the fourth day, and 71.7% in the indirect bioleaching on the fourth day, while in the controlled sterile flasks, Al leaching was almost negligible. A maximal amount of Al was leached by the fungal strains using low-cost molasses as a substrate.
Melanin is a natural pigment that can be applied in different fields such as medicine, environment, pharmaceutical, and nanotechnology. Studies carried out previously showed that the melanin produced ...by the mel1 mutant from Aspergillus nidulans exhibits antioxidant, anti-inflammatory, and antimicrobial activities, without any cytotoxic or mutagenic effect. These results taken together suggest the potential application of melanin from A. nidulans in the pharmaceutical industry. In this context, this study aimed to evaluate the effect of factors L-tyrosine, glucose, glutamic acid, L-DOPA, and copper on melanin production by the mel1 mutant and to establish the optimal concentration of these factors to maximize melanin production.
The results showed that L-DOPA, glucose, and copper sulfate significantly affected melanin production, where L-DOPA was the only factor that exerted a positive effect on melanin yield. Besides, the tyrosinase activity was higher in the presence of L-DOPA, considered a substrate required for enzyme activation, this would explain the increased production of melanin in this condition. After establishing the optimal concentrations of the analyzed factors, the melanin synthesis was increased by 640% compared to the previous studies.
This study contributed to elucidating the mechanisms involved in melanin synthesis in A. nidulans as well as to determining the optimal composition of the culture medium for greater melanin production that will make it possible to scale the process for a future biotechnological application.
In this study, an economical and sustainable bio-hydrometallurgical route was evaluated for the recovery of aluminum from low-grade bauxite using the marine-derived fungus Aspergillus niger. Firstly, ...four different solid media were tested for high-yield spore production. Organic acid production capacity by A. niger was also evaluated in a medium supplemented with glucose or low-cost molasses as a carbon source using fungal spores or pellets as inoculum. The concentrations of the produced organic acids were determined by High-Performance Liquid Chromatography (HPLC). The results showed that oat-agar can be used as an inexpensive solid medium for greater fungal sporulation, while the liquid medium supplemented with molasses as a low-cost carbon source can be used for higher organic acids production. Among the conditions tested, A. niger spore inoculum showed the highest yield of the total produced organic acids (122.40 g L−1 or 81.6% (grams of sucrose used per grams of total acid) and also the highest (1.02 ± 0.02 g L−1 h−1) acids production rate using molasses as an inexpensive carbon source. This cultivation condition was selected for the bioleaching studies with low-grade bauxite. Among the three different bioleaching methods tested, the direct two-steps bioleaching process resulted in higher aluminum leaching (91.2%) compared to indirect (84.8%) and direct one-step (82.8%) bioleaching process. According to the results obtained using marine-derived A. niger under the established culture conditions, proved to be an eco-friendly and cost-effective way for aluminum recovery from low-grade bauxite ore and has the potential to be adopted on a pilot scale.
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•Bio-hydrometallurgical route was studied for the recovery of aluminum from bauxite.•Oat-agar was selected as the best solid growth medium for the spore production.•Molasses was used as a carbon substrate for the production of fungal metabolites.•A. niger was successfully used to degrade the bauxite ore to liberate aluminum.•The direct two-steps bioleaching process showed the highest (91.2%) Al leaching.
Melanins are pigments of high molecular weight formed by oxidative polymerization of phenolic or indolic compounds. A number of fungi, including Aspergillus nidulans, produce pigments related or ...identical to melanin, which are located on cell walls or exist as extracellular polymers. The aim of the present study was to assess the antioxidant activity of synthetic melanin and of the pigment extracted from the mycelium and culture medium after growth of the highly melanized strain (MEL1) from A. nidulans. The ability of the melanin pigment to scavenge the oxidants HOCl and H2O2 was evaluated by inhibition of the oxidation of 5-thio-2-nitrobenzoic acid (TNB) using several melanin concentrations. The results showed that the pigment of the MEL1 strain competes with TNB for H2O2 and HOCl, inhibiting TNB oxidation in a concentration-dependent manner. For the HOCl oxidant, this inhibition was comparable to that of synthetic melanin, whose IC50 values were quite close for both pigments. Thus, our results suggest that the melanin from A. nidulans is a potential HOCl scavenger and may be considered a promising material for the cosmetic industry for the formulation of creams that protect the skin against possible oxidative damage.
Fungal pigments, including melanin, are recognized as promising materials for biomedical, environmental, and technological applications. In previous studies, we have demonstrated that the ...DOPA-melanin produced by the MEL1 mutant of
exhibits antioxidant, anti-inflammatory, and antimicrobial activities without any cytotoxic or mutagenic effects, suggesting its potential use in pharmaceuticals. In order to increase the yield of this pigment and reduce the costs of its large-scale production, the present study aimed to evaluate agro-industrial by-products, sugarcane molasses, vinasse, and corn steep liquor as inexpensive substrates for fungal growth using experimental design methodology. According to the results obtained, the optimal composition of the culture medium was 0.81% (
/
) vinasse and 1.62% (
/
) glucose, which promoted a greater production of melanin (225.39 ± 4.52 mg g
of biomass), representing a 2.25-fold increase compared with the condition before optimization (100.32 mg.g
of biomass). Considering the amount of biomass obtained in the optimized condition, it was possible to obtain a total melanin production of 1 g L
. Therefore, this formulation of a less complex and low-cost culture medium composition makes the large-scale process economically viable for future biotechnological applications of melanin produced by
The naturally occurring pigment, melanin is found in organisms of all phylogenetic kingdoms, including fungi, and exhibits a wide range of biological activities. Our objective was to investigate the ...effects of melanin extracted from the fungus Aspergillus nidulans on the production of the pro-inflammatory mediators nitric oxide (NO) and tumour necrosis factor-α (TNF-α) in peritoneal macrophages and on the viability of McCoy mouse fibroblasts. The results showed that A. nidulans melanin did not stimulate NO production in macrophages, but it inhibited the NO production in lipopolysaccharide (LPS)-stimulated macrophages by approximately 82%. Similarly, A. nidulans melanin inhibited LPS-stimulated TNF-α production by 52% and showed a slight stimulatory effect on TNF-α production in macrophages. In addition, the toxicity of A. nidulans melanin to McCoy cells was much lesser (IC50=373.5±2.4 µg/mL) than that of known agents such as cisplatin (IC50=41.2 µg/mL). The viability of peritoneal macrophages was greater than 90% at the highest melanin concentration tested (100 µg/mL). Thus, the combination of low cytotoxicity and marked inhibition of TNF-α and NO production suggests that A. nidulans melanin has potential as an anti-inflammatory agent and may be used in the future for development of new drugs with therapeutic utility.
Filamentous fungi have been proved to have a pronounced capability to recover metals from mineral ores. However, the metal recovery yield is reduced due to toxic effects triggered by various heavy ...metals present in the ore. The current study highlights the fungal adaptations to the toxic effects of metals at higher pulp densities for the enhanced bio-recovery of aluminum from low-grade bauxite. In the previous studies, a drastic decrease in the aluminum dissolution was observed when the bauxite pulp density was increased from 1 to 10% (w/v) due to the high metal toxicity and low tolerance of
Aspergillus niger
and
Penicillium simplicissium
to heavy metals
.
These fungi were adapted in order to increase heavy metal tolerance of these fungal strains and also to get maximum Al dissolution. A novel approach was employed for the adaptation of fungal strains using a liquid growth medium containing 5% bauxite pulp density supplemented with molasses as an energy source. The mycelia of adapted strains were harvested and subsequently cultured in a low-cost oat-agar medium. Batch experiments were performed to compare the aluminum leaching efficiencies in the direct one-step and the direct two-step bioleaching processes. FE-SEM analysis revealed the direct destructive and corrosive action by the bauxite-tolerant strains due to the extension and penetration of the vegetative mycelium filaments into the bauxite matrix. XRD analysis of the bioleached bauxite samples showed a considerable decline in oxide minerals such as corundum and gibbsite. Results showed a high amount of total Al (≥ 98%) was successfully bioleached and solubilized from low-grade bauxite by the adapted fungal strains grown in the presence of 5% pulp density and molasses as a low-cost substrate.
Graphical abstract
Context: A mutant that exhibited increased melanin pigment production was isolated from Aspergillus nidulans fungus. This pigment has aroused biotechnological interest due to its photoprotector and ...antioxidant properties. In a recent study, we showed that melanin from A. nidulans also inhibits NO and TNF-α production.
Objective: The present study evaluates the mutagenicity and cytotoxicity of melanin extracted from A. nidulans after its exposure to liver S9 enzymes.
Materials and methods: The cytotoxicity of multiple concentrations of melanin (31.2-500 μg/mL) against the McCoy cell line was evaluated using the Neutral Red assay, after incubation for 24 h. Mutagenicity was assessed using the Ames test with the Salmonella typhimurium strains TA98, TA97a, TA100, and TA102 at concentrations ranging from 125 μg/plate to 1 mg/plate after incubation for 48 h.
Results: The cytotoxicity of A. nidulans melanin after incubation with S9 enzymes was less than (CI
50
value= 413.4 ± 3.1 μg/mL) that of other toxins, such as cyclophosphamide (CI
50
value = 15 ± 1.2 μg/mL), suggesting that even the metabolised pigment does not cause significant damage to cellular components at concentrations up to 100 μg/mL. In addition, melanin did not exhibit mutagenic properties against the TA 97a, TA 98, TA 100, or TA 102 strains of S. typhimurium, as shown by a mutagenic index (MI) <2 in all assays.
Discussion and conclusion: The significance of these results supports the use of melanin as a therapeutic reagent because it possesses low cytotoxicity and mutagenic potential, even when processed through an external metabolising system.
Fungal pigments, including melanin, are recognized as promising materials for biomedical, environmental, and technological applications. In previous studies, we have demonstrated that the ...DOPA-melanin produced by the MEL1 mutant of Aspergillus nidulans exhibits antioxidant, anti-inflammatory, and antimicrobial activities without any cytotoxic or mutagenic effects, suggesting its potential use in pharmaceuticals. In order to increase the yield of this pigment and reduce the costs of its large-scale production, the present study aimed to evaluate agro-industrial by-products, sugarcane molasses, vinasse, and corn steep liquor as inexpensive substrates for fungal growth using experimental design methodology. According to the results obtained, the optimal composition of the culture medium was 0.81% (v/v) vinasse and 1.62% (w/v) glucose, which promoted a greater production of melanin (225.39 ± 4.52 mg gsup.−1 of biomass), representing a 2.25-fold increase compared with the condition before optimization (100.32 mg.gsup.−1 of biomass). Considering the amount of biomass obtained in the optimized condition, it was possible to obtain a total melanin production of 1 g Lsup.−1. Therefore, this formulation of a less complex and low-cost culture medium composition makes the large-scale process economically viable for future biotechnological applications of melanin produced by A. nidulans.
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