Aspergillus niger, which is a fungal pathogen, causes rot in a variety of fruits. In this study, the cystathionine β-synthase cbsA gene was deleted by homologous recombination to study its role in ...sulfur metabolism and pathogenicity of A. niger. The results showed that ΔcbsA strain maintained normal mycelia growth and sporulation compared with the control strain A. niger MA 70.15, whereas the contents of cysteine and glutathione (GSH) increased significantly after cbsA deletion. However, ΔcbsA strain showed reduced endogenous H2S production. Further results showed that cbsA gene deletion induced higher resistance to cadmium stress and stronger infectivity to pears. It was also found that a stronger response of reactive oxygen species (ROS) production was induced in ΔcbsA mutant-infected pear compared with the control strain. In all, the present research suggested the important role of cbsA in sulfur metabolism and pathogenicity of A. niger in pear fruit.
•Fusion expression enhanced the secretion of an acidic lipase in Pichia pastoris.•The fusion acidic lipase showed a higher catalytic efficiency than the parent.•The fusion acidic lipase is a suitable ...candidate for promoting gastric digestion.
The low expression level of acidic lipases from Aspergillus sp. remains a major obstacle for their use in industrial applications. In this study, fusion expression with three fusion partners was investigated to enhance the expression level of an acidic lipase from A. niger (ANL) in Pichia pastoris. When fused with a small ubiquitin-related modifier (SUMO), designated SANL, the highest activity reached 960 ± 40 U/mL in a 3 L fermenter, which was 1.85-fold higher than that of the parent ANL. SANL exhibited its maximum activity at pH 2.5 and had lower Km and higher kcat/Km values than those of ANL. In gastrointestinal digestion experiments, SANL was resistant to pepsin and had high hydrolytic activity against triolein from pH 3.0 to 6.0. However, SANL was significantly inhibited by NaTDC above its CMC, which may limit its application for intestinal digestion, but allow it to remain suitable for gastric digestion.
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•Optimization of four organic acids produced by Aspergillus niger was performed.•Sucrose concentration is the most important factor for producing organic acids.•LIBs leaching test in ...optimum conditions through spent medium bioleaching was done.•Cu, Li, Mn, and Al recovery was highest at 2% and for Co and Ni at 1% pulp density.
In the present study, spent medium bioleaching method was performed using organic acids produced by Aspergillus niger to dissolve Ni, Co, Mn, Li, Cu and Al from spent lithium-ion batteries (LIBs). Response surface methodology was used to investigate the effects and interactions between the effective factors of sucrose concentration, initial pH, and inoculum size to optimize organic acid production. Maximum citric acid, malic acid, and gluconic acid concentrations of 26,478, 1832.53 and 8433.76ppm, respectively, and a minimum oxalic acid concentration of 305.558ppm were obtained under optimal conditions of 116.90 (gl−1) sucrose concentration, 3.45% (vv−1) inoculum size, and a pH value of 5.44. Biogenically-produced organic acids are used for leaching of spent LIBs at different pulp densities. The highest metal recovery of 100% Cu, 100% Li, 77% Mn, and 75% Al occurred at 2% (wv−1) pulp density; 64% Co and 54% Ni recovery occurred at 1% (wv−1) pulp density. The bioleaching of metals from spent LIBs can decrease the environmental impact of this waste. The results of this study suggest that the process can be used for large scale industrial purposes.
Pectinase enzymes present a high priced category of microbial enzymes with many potential applications in various food and oil industries and an estimated market share of $ 41.4 billion by 2020.
The ...production medium was first optimized using a statistical optimization approach to increase pectinase production. A maximal enzyme concentration of 76.35 U/mL (a 2.8-fold increase compared with the initial medium) was produced in a medium composed of (g/L): pectin, 32.22; (NH
)
SO
, 4.33; K
HPO
, 1.36; MgSO
.5H
O, 0.05; KCl, 0.05; and FeSO
.5H
O, 0.10. The cultivations were then carried out in a 16-L stirred tank bioreactor in both batch and fed-batch modes to improve enzyme production, which is an important step for bioprocess industrialization. Controlling the pH at 5.5 during cultivation yielded a pectinase production of 109.63 U/mL, which was about 10% higher than the uncontrolled pH culture. Furthermore, fed-batch cultivation using sucrose as a feeding substrate with a rate of 2 g/L/h increased the enzyme production up to 450 U/mL after 126 h.
Statistical medium optimization improved volumetric pectinase productivity by about 2.8 folds. Scaling-up the production process in 16-L semi-industrial stirred tank bioreactor under controlled pH further enhanced pectinase production by about 4-folds. Finally, bioreactor fed-batch cultivation using constant carbon source feeding increased maximal volumetric enzyme production by about 16.5-folds from the initial starting conditions.
Itaconic acid is a five-carbon dicarboxylic acid with an unsaturated alkene bond, frequently used as a building block for the industrial production of a variety of synthetic polymers. It is also one ...of the major products of fungal “overflow metabolism” which can be produced in submerged fermentations of the filamentous fungus
Aspergillus terreus
. At the present, molar yields of itaconate are lower than those obtained in citric acid production in
Aspergillus niger
. Here, we have studied the possibility that the yield may be limited by the oxygen supply during fermentation and hence tested the effect of the dissolved oxygen concentration on the itaconic acid formation rate and yield in lab-scale bioreactors. The data show that a dissolved oxygen concentration of 2% saturation was sufficient for maximal biomass formation. Raising it to 30% saturation had no effect on biomass formation or the growth rate, but the itaconate yield augmented substantially from 0.53 to 0.85 mol itaconate/mol glucose. Furthermore, the volumetric and specific rates of itaconic acid formation ameliorated by as much as 150% concurrent with faster glucose consumption, shortening the fermentation time by 48 h. Further increasing the dissolved oxygen concentration over 30% saturation had no effect. Moreover, we show that this increase in itaconic acid production coincides with an increase in alternative respiration, circumventing the formation of surplus ATP by the cytochrome electron transport chain, as well as with increased levels of alternative oxidase transcript. We conclude that high(er) itaconic acid accumulation requires a dissolved oxygen concentration that is much higher than that needed for maximal biomass formation, and postulate that the induction of alternative respiration allows the necessary NADH reoxidation ratio without surplus ATP production to increase the glucose consumption and the flux through overflow metabolism.
Summary The antifungal activity of bacteria from the genus Collimonas has been well documented, but the chemistry and gene functions that underlie this phenotype are still poorly understood. ...Screening of a random plasposon insertion library of Collimonas fungivoransTer331 for loss-of-function mutants revealed the importance of gene cluster K, which is annotated to code for the biosynthesis of a secondary metabolite and which features genes for fatty acid desaturases and polyketide synthases. Mutants in gene cluster K had lost the ability to inhibit hyphal growth of the fungus Aspergillus niger and were no longer able to produce and secrete several metabolites that after extraction and partial purification from wildtype strain Ter331 were shown to share a putative ene-triyne moiety. Some but not all of these metabolites were able to inhibit growth of A.niger, indicating functional variation within this group of Collimonas-produced polyyne-like 'collimomycins'. Polymerase chain reaction analysis of isolates representing different Collimonas species indicated that the possession of cluster K genes correlated positively with antifungal ability, further strengthening the notion that this cluster is involved in collimomycin production. We discuss our findings in the context of other bacterially produced polyynes and the potential use of collimomycins for the control of harmful fungi. PUBLICATION ABSTRACT
•Solid-state fermentation (SSF) of plum by-products with A. niger and R. oligosporus.•Phenolic compounds and antioxidant levels increased significantly by SSF.•Plum kernel oil yield increased by ...21.90% for SSF with A. niger.•Polar lipids were enriched with n-3 polyunsaturated fatty acids.
Evolutions of phenolic contents and antioxidant activities during solid-state fermentation (SSF) of plum pomaces (from the juice industry) and brandy distillery wastes with Aspergillus niger and Rhizopus oligosporus were investigated. The effect of fermentation time on the oil content and major lipid classes in the plum kernels was also studied. Results showed that total phenolic (TP) amounts increased by over 30% for SSF with Rhizopus oligosporus and by >21% for SSF with A. niger. The total flavonoid contents presented similar tendencies to those of the TPs. The free radical scavenging activities of methanolic extracts were also significantly enhanced. The HPLC-MS analysis showed that quercetin-3-glucoside was the major phenolic compound in both fermented plum by-products. The results also demonstrated that SSF not only helped to achieve higher lipid recovery from plum kernels, but also resulted in oils with better quality attributes (high sterol ester and n-3 PUFA-rich polar lipid contents).
Microbial assisted biosynthesis of nanoparticles is a rapidly progressing area of nanobiotechnology. In this paper
Aspergillus niger assisted extracellular synthesis of silver nanoparticles is ...reported. The silver nanoparticles were characterized by UV–vis spectrophotometry, TEM, EDX and FTIR. TEM studies showed the size of the silver nanoparticles to be in the range of 3–30
nm. The probable mechanism for the extracellular synthesis of silver nanoparticles by
Aspergillus niger was investigated. The nanoparticles showed antimicrobial activity against fungal and bacterial strains.
Aspergillus niger mycelial waste is a good raw material for production of N-acetyl-d-glucosamine (GlcNAc). In this study, AnChiB, an A. niger chitinase which is upregulated during autolysis, was ...found to degrade A. niger mycelial waste with high efficiency. It could produce 1.45 mM (GlcNAc)2 in 8 h from raw mycelial waste, outperforming other chitinases, including bacterial SmChiA, human HsCht, and insect OfChtI and OfChi-h. The crystal structure of AnChiB was determined, and residues Trp106 and Trp118 were found to be important for the activity of AnChiB toward mycelial waste; mutation of either Trp106 or Trp118 into phenylalanine or alanine resulted in dramatically decreased activity. A recombinant strain of Bacillus subtilis was constructed to extracellularly produce AnChiB, and the culture supernatant was used to treat mycelial waste. This eco-friendly strategy could produce 3.7 mM of GlcNAc from 10 g of mycelial waste in 94 h with a yield of 71.3%.
► New bioprocesses for the production of cellulolytic enzymes are needed. ► A novel combined cultivation method for cellulase production is being proposed. ► The new method resulted in a 3-fold ...improvement over conventional fermentation.
Sequential solid-state and submerged cultivation with sugarcane bagasse as substrate for cellulase production by Aspergillus niger A12 was assessed by measuring endoglucanase activity. An unconventional pre-culture with an initial fungal growth phase under solid-state cultivation was followed by a transition to submerged fermentation by adding the liquid culture medium to the mycelium grown on solid substrate. For comparison, control experiments were conducted using conventional submerged cultivation. The cultures were carried out in shake flasks and in a 5-L bubble column bioreactor. An endoglucanase productivity of 57±13IU/L/h was achieved in bubble column cultivations prepared using the new method, representing an approximately 3-fold improvement compared to conventional submerged fermentation. Therefore, the methodology proposed here of a sequential fermentation process offers a promising alternative for cellulase production.
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