Abstract
Streptomyces sp. TD-1 was identified as Streptomyces alboflavus based on its morphological characteristics, physiological properties, and 16S rDNA gene sequence analysis. The antifungal ...activity of the volatile-producing S. alboflavus TD-1 was investigated. Results showed that volatiles generated by S. alboflavus TD-1 inhibited storage fungi Fusarium moniliforme Sheldon, Aspergillus flavus, Aspergillus ochraceus, Aspergillus niger, and Penicillum citrinum in vitro. GC/MS analysis revealed that 27 kinds of volatile organic compounds were identified from the volatiles of S. alboflavus TD-1 mycelia, among which the most abundant compound was 2-methylisoborneol. Dimethyl disulfide was proved to have antifungal activity against F. moniliforme by fumigation in vitro.
Combination of statistical optimization and mutagenesis to isolate hypersecretory strains is studied to maximize phytase production from
Aspergillus niger
NCIM 563 under submerged fermentation. The ...overall results obtained show a remarkable 5.98-fold improvement in phytase production rates when compared to that using basal medium. Optimization of culture conditions from parent strain is studied first by the Plackett–Burman technique to evaluate the effects of 11 variables for phytase production. The results showed that glucose, MgSO
4
, KCl, incubation period, and MnSO
4
are the most significant variables affecting enzyme production. Further optimization in these variables, using a central composite design technique, resulted in 3.74-fold increase in the yield of phytase production to 254,500 U/l when compared with the activity observed with basal media (68,000 U/l) in shake flask. Our experiments show that the phytase from
A. niger
NCIM 563 exhibits desirable activity in simulated gastric fluid conditions with low pH and also improved thermostability when compared to commercial phytase. The improved yield demonstrates the potential applicability of phytase enzyme as a source of phytase supplement for phosphorus nutrition and environmental protection in animal feed industry. Physical and chemical mutagenesis experiments were carried out in parallel to isolate hypersecretory mutants that could possibly further enhance the enzyme production. Using optimized media conditions of the parent strain, our results show that mutant strain
A. niger
NCIM 1359 increased the phytase activity by another 1.6-fold to 407,200 U/l.
•Smart starch/PVA film having color indication and antimicrobial properties was developed.•The real-time pH variation of foods can be monitored by the color change of the film.•The film can ...effectively inhibit pathogen growth such as Staphylococcus aureus.
We have developed an intelligent starch/poly-vinyl alcohol (PVA) film that is capable of monitoring pH changes and inhibiting undesired microbial growth in foods. Starch and PVA polymers in the film were doubly cross-linked by sodium trimetaphosphate and boric acid to improve their water-resistance and mechanical strength. Anthocyanins (ANT) and limonene (LIM) were used to achieve simultaneous colorimetric indication and antimicrobial activity. Firstly, the characterization of surface morphology using SEM confirmed that the starch-PVA-ANT-LIM film possessed a smooth surface. Secondly, the results of the mechanical strength test showed that starch-PVA-ANT-LIM possesses the highest mechanical strength. Additionally, there was a distinguishable change of colors as the film was immersed in solutions of pH ranging from 1.0 to 14.0. Moreover, the film showed excellent antimicrobial activity for three typical undesired microorganisms in foods, Bacillus subtilis, Aspergillus niger, and Staphylococcus aureus. Finally, the film exhibited good color indication and antimicrobial activity on pasteurized milk. The results suggest that the intelligent film reported here shows good capability for both alerting and inhibiting food spoilage.
•Extremely low frequency magnetic field (ELF−MF) exposure can notably enhance glucose oxidase expression in Pichia pastoris.•Significant changes in cells behavioral took place at ELF of 2.8 Hz ...regardless of increase or decrease in magnetic fields intensity.•The GOX production increase under ELF-MF exposure is not relative to changes in biomass production, protease activity and yeast viability.
In this study attempts were made to investigate the effect of extremely low frequency magnetic field (ELF-MF) on expression of glucose oxidase gene from Aspergillus niger Z-25 in Pichia pastoris GS115 at optimal environmental conditions.
GOX encoding gene from A. niger was expressed in P. pastoris GS115 employing methanol inducible AOX1 promoter. From resistant transformants to high zeocin concentrations, maximum GOX expressing transformant was isolated and used throughout the study. Optimal environmental conditions for achieving maximum glucose oxidase (GOX) production was determined by varying temperature (20–30°C) and final methanol concentration from 0.25–1% (v/v). Maximum GOX production was obtained at 20°C and 0.25% (v/v) final methanol concentration. Exposure carried out at extremely low frequencies ranging from 1 to 5Hz and the field strength of 30–100mT unceasingly. Biomass, GOX, protease productions and cell viability were examined in exposed and non-exposed groups every 12h up to 96h. Among different exposure conditions, the frequency of 2.8Hz significantly increased GOX production and cell viability, decreased non-specific protease activity and improved biomass production regardless of changes in field intensity. Overall, supported by results, P. pastoris exposure to ELF-MF in certain circumstances could effectively further increase maximum production of GOX as achieved by optimized preliminary environmental parameters.
Itaconic acid (IA), an unsaturated dicarboxylic acid with a high potential as a platform for chemicals derived from sugars, is industrially produced by large-scale submerged fermentation by ...Aspergillus terreus. Although the biochemical pathway and the physiology leading to IA is almost the same as that leading to citric acid production in Aspergillus niger, published data for the volumetric (g L⁻¹) and the specific yield (mol/mol carbon source) of IA are significantly lower than for citric acid. Citric acid is known to accumulate to high levels only when a number of nutritional parameters are carefully adjusted, of which the concentration of the carbon source and that of manganese ions in the medium are particularly important. We have therefore investigated whether a variation in these two parameters may enhance IA production and yield by A. terreus. We show that manganese ion concentrations < 3 ppb are necessary to obtain highest yields. Highest yields were also dependent on the concentration of the carbon source (D-glucose), and highest yields (0.9) were only obtained at concentrations of 12–20 % (w/v), thus allowing the accumulation of up to 130 g L⁻¹ IA. These findings perfectly mirror those obtained when these parameters are varied in citric acid production by A. niger, thus showing that the physiology of both processes is widely identical. Consequently, applying the fermentation technology established for citric acid production by A. niger citric acid production to A. terreus should lead to high yields of IA, too.
Glucose oxidase is one of the most conspicuous commercial enzymes due to its many different applications in diverse industries such as food, chemical, energy and textile. Among these applications, ...the most remarkable is the manufacture of glucose biosensors and in particular sensor strips used to measure glucose levels in serum. The generation of ameliorated versions of glucose oxidase is therefore a significant biotechnological objective. We have used a strategy that combined random and rational approaches to isolate uncharacterized mutations of Aspergillus niger glucose oxidase with improved properties. As a result, we have identified two changes that increase significantly the enzyme's thermal stability. One (T554M) generates a sulfur-pi interaction and the other (Q90R/Y509E) introduces a new salt bridge near the interphase of the dimeric protein structure. An additional double substitution (Q124R/L569E) has no significant effect on stability but causes a twofold increase of the enzyme's specific activity. Our results disclose structural motifs of the protein which are critical for its stability. The combination of mutations in the Q90R/Y509E/T554M triple mutant yielded a version of A. niger glucose oxidase with higher stability than those previously described.
The cell wall of animal feed grains contain a high proportion of xylan. Monogastric farm animals lack xylan-hydrolyzing enzymes in their gastro-intestinal tract. The indigestible dietary xylan ...impairs normal digestive function of single-stomached livestock by preventing efficient breakdown and assimilation of feed nutrients. The digestive capability of simple-stomached animals could be improved by providing them with a foreign xylanase gene for secretion of the enzyme into their digestive tract. In this study, we produced transgenic mice carrying an Aspergillus niger xylanse gene controlled by a salivary gland-specific regulatory element. The fungal xylanase is expressed specifically in the submandibular gland and secreted in the saliva of transgenic mice. The xylanase concentration in the saliva of transgenic mice reached 0.29 plus or minus 0.03 U/ml. Digestibility of nutrients tends to increase in transgenic mice, although it does not differ significantly from that in wild-type controls. To our knowledge, this is the first demonstration of the production of fungal xylanase in the saliva of simple-stomached animals. Results from the present study encourage further investigation of employing transgenic technology to enhance the digestive capability of monogastric agriculture animals by introducing enzyme able to degrade dietary xylan into the digestive tract.
A novel two-step high-throughput strategy was developed for screening of gluconate high-yield strains by Aspergillus niger. The first step was fast qualitative assay according to the indicator color ...change, the second step was quantitative assay according to the absorbance of chelate formed with Cu2+ at 810nm. The accuracy of high-throughput assay was comparable to that of high-performance liquid chromatography (HPLC). The correlation coefficient between CuSO4 assay and HPLC assays was exceeding 0.99 by statistical analysis. As a result, 3 high-yield mutants were screened out from 1000 viable single colonies, the mutants II-2-A1, IV-7-C6, and V-11-C5 were further validated in 5L of bioreactor. The average production rates were 15.5%, 32.8%, and 12.1% higher than that of the parental strain, respectively.
•We developed a two-step selection strategy to screen large libraries of mutants.•Bromocresol green was added in media resulted in a real-time monitoring system.•Three effective mutants were screened out by high-throughput screening strategy.
The corrosion behavior of anodized and non-anodized aluminum alloy 6061 in the presence of Aspergillus niger fungus was studied using electrochemical noise, recurrence plots and electrochemical ...impedance spectroscopy techniques. Corrosion potential measurements were also obtained. The fungus generated organic acids causing microbially induced corrosion of the specimens, which was more evident on non-anodized than on anodized aluminum alloy 6061, showing uniform and localized corrosion and a change in the attack as a function of the fungus growth time. A biomass growth curve was obtained to compare the behavior of anodized and non-anodized aluminum alloy 6061. A long-term electron transfer mechanism was proposed for localized corrosion of aluminum alloy 6061.
Figure shows impedance plots of non-anodized aluminum alloy AA 6061 in the presence of Aspergillus niger at 2, 6, 8 and 15 days, and electrical equivalent circuit model used to fit impedance data (upper part), where Rs corresponds to the solution resistance, CPE is a constant phase element, R1 is the charge transfer resistance, R2 and C correspond to adsorption-desorption and surface coverage processes, respectively. The shape of the impedance diagrams is similar for the four experimental times, a capacitive behavior showing a depressed semicircle at high frequency (from 10 kHz to ∼0.1 Hz), with the center lying below the real axis, and an inductive behavior showing a loop below the real axis at low frequencies (from ∼0.1 Hz to 0.05 Hz), which is a typical loop shape of an adsorption process and may be associated with the adherence of spores to the metallic surface, originating differential aeration cells which may produce localized corrosion. Display omitted
•Corrosion of aluminum alloy 6061 in the presence of A. niger was studied.•A. niger generated citric acid causing corrosion on aluminum alloy 6061 specimens.•The highest corrosion at day 8 corresponding to the maximum microorganism growth.•Biomass growth curves for anodized and non-anodized aluminum alloy 6061 specimens.
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