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There is no study and data about aerial mycelium biosorbents for heavy metal removal. In previous investigations, Aspergillus niger biosorbents were made of vegetative mycelium, called mycelium pellets, which were obtained from th...
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There is no study and data about aerial mycelium biosorbents for heavy metal removal. In previous investigations, Aspergillus niger biosorbents were made of vegetative mycelium, called mycelium pellets, which were obtained from the fermentation of a liquid medium, and usually needed lots of procedures to produce. This work therefore was novel that the mycelium of Aspergillus niger were scraped directly from the surface of solid medium (cultivated 7 d) as a kind of biosorbent, called aerial mycelium. In biosorption experiments, aerial mycelium exhibited a short biosorption equilibrium time of 30 min, high copper biosorption capacity (100 mg/g) and high removal efficiency at a pH range of 4.0-6.0. The main Cu2+ biosorption mechanism were electrostatic attraction and Cu2+ ion exchange with K+, Na+, Mg2+ and Ca2+, together with chelation with functional groups such as -COOH, -NH2, -PO43-, and -OH. The biosorption data obtained were well described by the pseudo-second-order kinetic model and the Freundlich isotherm model. In addition, because aerial mycelium can grow on many kinds of moist agro-industrial waste materials, it could be becoming a potential biosorbent in large-scale industrial wastewater treatment.
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Supplementation with silicate microparticles was used as novel approach to control the morphological development of Aspergillus niger, important as the major world source of citric acid and higher-value enzymes, in submerged cultu...
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Supplementation with silicate microparticles was used as novel approach to control the morphological development of Aspergillus niger, important as the major world source of citric acid and higher-value enzymes, in submerged culture. With careful variation of size and concentration of the micromaterial added, a number of distinct morphological forms including pellets of different size, free dispersed mycelium, and short hyphae fragments could be reproducibly created. Aluminum oxide particles similarly affected morphology, showing that this effect is largely independent of the chemical particle composition. Image analysis of morphological development of A. niger during the cultivation process showed that the microparticles influence the morphology by collision-induced disruption of conidia aggregates and probably also the hindrance of new spore–spore interactions in the very early stage of the process. Exemplified for different recombinant A. niger strains enzyme production could be strongly enhanced by the addition of microparticles. Linked to the formation of freely dispersed mycelium, titers for glucoamylase (GA) expressed as intracellular enzyme (88 U/mL) and fructofuranosidase secreted into the supernatant (77 U/mL), were up to fourfold higher in shake flasks. Moreover, accumulation of the undesired by-product oxalate was suppressed by up to 90%. The microparticle strategy could be successfully transferred to fructofuranosidase production in bioreactor, where a final titer of 160 U/mL could be reached. Using co-expression of GA with green fluorescent protein, enzyme production was localized in the cellular aggregates of A. niger. For pelleted growth, protein production was maximal only within a thin layer at the pellet surface and markedly decreased in the pellet interior, whereas the interaction with the microparticles created a highly active biocatalyst with the dominant fraction of cells contributing to production.
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A Phanerochaete chrysosporium-based aerobic granular sludge (PC-AGS) was developed by inoculating fungal mycelial pellets into a lab-scale aerobic granular sequencing batch reactor (AGSBR). A strategy using step-anaerobic feeding ...
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A Phanerochaete chrysosporium-based aerobic granular sludge (PC-AGS) was developed by inoculating fungal mycelial pellets into a lab-scale aerobic granular sequencing batch reactor (AGSBR). A strategy using step-anaerobic feeding coupled with multi A/O conditions was adopted. The results showed that the removal efficiencies for total phosphorus (TP) and total inorganic nitrogen (TIN) were 94.56 +/- 2.92% and 75.20 +/- 7.74%, respectively, under relatively low aeration time. Compared with original AGS, the content of extracellular proteins for PC-AGS obviously increased from 18.61 to 41.44 mg/g MLSS by the end of phase I. Moreover, the mature granules had a larger size and better stability during the 100 days operation. Furthermore, the analysis of microbial diversity detected many key functional groups in PC-AGS granules that were beneficial to nutrients removal. This work demonstrated that the addition of fungal pellets not only enhanced the removal performance, but also improved the stability of the AGS system.
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The coexistence of multiple pollutants and lack of carbon sources are challenges for the biological treatment of wastewater. To achieve simultaneous removal of nitrate (NO3--N) and cadmium (Cd2+) at low carbon to nitrogen (C/N) ra...
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The coexistence of multiple pollutants and lack of carbon sources are challenges for the biological treatment of wastewater. To achieve simultaneous removal of nitrate (NO3--N) and cadmium (Cd2+) at low carbon to nitrogen (C/N) ratios, 2-hydroxy-1,4-naphthoquinone (HNQ) was selected from three redox mediators as an accelerator for denitrification of heterotrophic strain Pseudomonas stutzeri sp. GF2 and autotrophic strain Zoogloea sp. FY6. Then, halloysite nanotubes immobilized with 2-hydroxy-1,4-naphthoquinone (HNTs-HNQ) were prepared and a bioreactor was constructed with immobilized redox mediator granules (IRMG) as the carrier, which was immobilized with HNTs-HNQ and inoculated with the two strains. The immobilized HNQ and the inoculated strains jointly improved the removal ability of NO3--N and Cd2+ and the removal efficiency of NO3--N (25.0 mg L-1) and Cd2+ (5.0 mg L-1) were 92.81% and 93.94% at C/N = 1.5 and hydraulic retention time (HRT) = 4 h. The Cd2+ was removed by adsorption of iron oxides (FeO(OH) and Fe3O4) and IRMG. The electron transport system activity (ETSA) of bacteria was improved and the composition of dissolved organic matter in the effluent was not affected by HNQ. The HNQ promoted the production of FeO(OH) and up-regulated the proportion of Zoogloea (54.75% in the microbial community), indicating that Zoogloea sp. FY6 was dominant in the microbial community. In addition, HNQ influenced the metabolic pathways and improved the relative abundance of some genes involved in nitrogen metabolism and the iron redox cycle.
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Dye pollution has become a major threat to the environment. Advanced oxidation processes (AOPs) are widely used in dye wastewater treatment, and the selection of catalyst is of great significance. In this study, a novel composite ...
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Dye pollution has become a major threat to the environment. Advanced oxidation processes (AOPs) are widely used in dye wastewater treatment, and the selection of catalyst is of great significance. In this study, a novel composite material OMS-2/hyphae was prepared through self-assembly technique. Mycelium pellets of carrier material were prepared using a waste biomass resource as the medium of Aspergillus niger. The composite material was characterized by polarized light microscopy (PLM), X-ray diffraction (XRD), Fourier-transform infrared spectrometer (FTIR), and scanning electron microscope (SEM). The results showed that the mycelium pellet was an applicable biocarrier material for successful loading of nano OMS-2 with nearly no changes of structure. To explore the catalytic properties of such material, reactive brilliant red X-3B was selected as pollutant. The degradation capacity brought by composite material was up to 80% within 35 min, which was much higher than that with the pure OMS-2 or mycelium pellet. After four cycles, the degradation efficiency of dye was maintained above 50%, and the material was remained stable. This study provided some useful information for the application of environmentally friendly biomass material in wastewater treatment.
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Filamentous microorganisms are important work horses in industrial biotechnology and supply enzymes, antibiotics, pharmaceuticals, bulk and fine chemicals. Here we highlight recent findings on the use of microparticles in the cult...
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Filamentous microorganisms are important work horses in industrial biotechnology and supply enzymes, antibiotics, pharmaceuticals, bulk and fine chemicals. Here we highlight recent findings on the use of microparticles in the cultivation of filamentous bacteria and fungi, with the aim of enabling a more precise control of their morphology towards better production performance. First examples reveal a broad application range of microparticle based processes, since multiple filamentous organisms are controllable in their growth characteristics and respond by enhanced product formation.
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Citric acid is an important platform chemical that is mainly produced by submerged fermentation of Aspergillus niger. However, seed preparation and citric acid production of Aspergillus niger under the current process are both ine...
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Citric acid is an important platform chemical that is mainly produced by submerged fermentation of Aspergillus niger. However, seed preparation and citric acid production of Aspergillus niger under the current process are both inefficient. In this study, a semicontinuous seed cultivation process was constructed by controlling the morphology of Aspergillus niger. The results of this study indicated that direct re-use of mycelium pellets lead to a rapid drop in both pellet quantity and rate of citric acid formation. Using morphology-based mycelium pellet dispersion, biomass remained at 95.1% after 38 cycles (468 h) with improved citric acid production. Size of mycelium fragments, incubation time, and segmentation proportion were treated as key factors to affect the steady-state of semicontinuous cultivation. The new technique saved over half of the seed preparation time and reduced spore usage to 1/38 that of the conventional batch seed culture. The small mycelium pellets formed from dispersed mycelium fragments also exhibited improved citric acid yield and productivity in the pilot-scale fermentation. Specifically, the rate of citric acid productivity increased by 19.3%. Finally, the citric acid concentration reached 193.4 g/L on a 5000 L production scale. This technique provides a valuable reference for production process optimization using filamentous fungi.
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The accumulation of volatile fatty acids and high osmotic pressure of food waste usually result in poor operation performance and even failure of anaerobic digestion (AD). A novel Fe3O4 nanoparticles-modified Aspergillus tubingens...
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The accumulation of volatile fatty acids and high osmotic pressure of food waste usually result in poor operation performance and even failure of anaerobic digestion (AD). A novel Fe3O4 nanoparticles-modified Aspergillus tubingensis (AT) mycelium pellets-based anaerobic granular sludge (NPs@AT-AGS) was therefore developed to enhance energy recovery efficiency of food waste AD treatment. The AT mycelium particles, with three-dimensional spatial structure formed by large amounts of hyphae, served as support to attach activated sludge microbes. The Fe3O4 nanoparticles (NPs) stimulated extracellular polymeric substances (EPS) secretion of AT mycelium pellets to 117.55 mg/gVSS, and further increased the microbe absorption quantity to 1.23 g/gAT. The abundant EPS of the NPs@AT-AGS could protect microbes from high osmotic pressure, which resulted in a methane yield of 583.8 mL/gVS under a high salinity of 20 g/L NaCl, 1.6 times higher than that of the activated flocculent sludge (AFS). Moreover, the methane yield of actual food with high organic load also had a 24% improvement with the NPs@AT-AGS. Therefore, the NPs@AT-AGS is promising in the effective AD treatment of food waste with high salinity and organic load.& nbsp;(c) 2021 Elsevier Ltd. All rights reserved.
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This research aims to elucidate the effect of fungal pellets (FP) on denitrifying bacteria regarding nitrate (NO_3~--N) removal, extracellular polymeric substances (EPS), and potential functions at a low carbon to nitrogen (C/N) r...
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This research aims to elucidate the effect of fungal pellets (FP) on denitrifying bacteria regarding nitrate (NO_3~--N) removal, extracellular polymeric substances (EPS), and potential functions at a low carbon to nitrogen (C/N) ratio. A symbiotic system of FP and denitrifying bacteria GF2 was established. The symbiotic system showed 100% NO_3~--N removal efficiency (4.07 mg L~(-1) h~(-1)) at 6 h and enhanced electron transfer capability at C/N = 1.5. The interactions between FP and denitrifying bacteria promoted the production of polysaccharides (PS) in EPS. Both the increased PS and the PS provided by FP as well as protein and humic acid-like substances in EPS could be consumed by denitrifying bacteria. FP acted as a protector and provided habitat and nutrients for denitrifying bacteria as well as improved the ability of carbohydrate metabolism, amino metabolism, and nitrogen metabolism of denitrifying bacteria. This study provides a new perspective on the relationship between FP and denitrifying bacteria.
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The long start-up time and facile biomass loss of aerobic granular sludge (AGS) impede its application for actual wastewater treatment. The present study investigates a novel assist-aggregation strategy based on Aspergillus tubing...
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The long start-up time and facile biomass loss of aerobic granular sludge (AGS) impede its application for actual wastewater treatment. The present study investigates a novel assist-aggregation strategy based on Aspergillus tubingensis (AT) mycelium pellets to accelerate sludge granulation, and engineered Fe_3O_4 nanoparticles (NPs) were used to further enhance flocculent sludge (FS) aggregation. The AT mycelium pellets, modified by 0.5 g/L Fe_3O_4@SiO_2-QC NPs (AT-V), had a more compact internal structure than the unmodified group (AT-I). The content of extracellular polymeric substances (EPS) and the zeta potential values were observed to increase from 39.86 mg/gVSS and -9.19 mv for AT-I to 69.64 mg/gVSS and 235 mv for AT-V, respectively. In optimized cultivation conditions, the aggregated sludge biomass of AT-V reached 1.54 g/g. An original AT-based AGS (AT-AGS) with a high biological activity (64.45 mgO_2/gVSSh as specific oxygen uptake rate) and enhanced velocity (58.22 m/h) was developed in only 9 days. The removal efficiencies of total nitrogen (TN) and total phosphorus (TP) of the AT-AGS were 12.24% and 16.29% higher than those of the inoculated FS under high feeding load. Additionally, the analysis of cyclic diguanylate (c-di-GMP) and con-focal microscope images implied that polysaccharide (PS) of EPS played an important role in maintaining the stability of the AT-AGS. Finally, the dominant functional species contributing to sludge aggregation and pollutants removal of the AT-AGS showed a larger richness and diversity than those of the inoculated FS. This study might provide a novel high-efficiency strategy for the fast formation of AGS.
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