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Critical Reviews in Microbiology Nov 2020Microbial citric acid has high economic importance and widely used in beverage, food, detergents, cosmetics and pharmaceutical industries. The filamentous fungus is a... (Review)
Review
Microbial citric acid has high economic importance and widely used in beverage, food, detergents, cosmetics and pharmaceutical industries. The filamentous fungus is a work horse and important cell factory in industry for the production of citric acid. Although in-depth literatures and reviews have been published to explain the biochemistry, biotechnology and genetic engineering study of citric acid production by separately but the present review compiled, all the aspects with upto date brief summary of the subject describing microorganisms, substrates and their pre-treatment, screening, fermentation techniques, metabolic engineering, biochemistry, product recovery and numerous biotechnological application of citric acid for simple understanding of microbial citric acid production. The availability of genome sequence of this organism has facilitated numerous studies in gene function, gene regulation, primary and secondary metabolism. An attempt has been also made to address the molecular mechanisms and application of recent advanced techniques such as CRISPR/Cas9 systems in enhancement of citric acid production.
Topics: Aspergillus niger; Biotechnology; Citric Acid; Fungal Proteins; Metabolic Engineering; Secondary Metabolism
PubMed: 33044884
DOI: 10.1080/1040841X.2020.1828815 -
Essays in Biochemistry Jul 2021The filamentous ascomycete fungus Aspergillus niger is a prolific secretor of organic acids, proteins, enzymes and secondary metabolites. Throughout the last century,... (Review)
Review
The filamentous ascomycete fungus Aspergillus niger is a prolific secretor of organic acids, proteins, enzymes and secondary metabolites. Throughout the last century, biotechnologists have developed A. niger into a multipurpose cell factory with a product portfolio worth billions of dollars each year. Recent technological advances, from genome editing to other molecular and omics tools, promise to revolutionize our understanding of A. niger biology, ultimately to increase efficiency of existing industrial applications or even to make entirely new products. However, various challenges to this biotechnological vision, many several decades old, still limit applications of this fungus. These include an inability to tightly control A. niger growth for optimal productivity, and a lack of high-throughput cultivation conditions for mutant screening. In this mini-review, we summarize the current state-of-the-art for A. niger biotechnology with special focus on organic acids (citric acid, malic acid, gluconic acid and itaconic acid), secreted proteins and secondary metabolites, and discuss how new technological developments can be applied to comprehensively address a variety of old and persistent challenges.
Topics: Aspergillus niger; Biotechnology; Citric Acid; Gene Editing
PubMed: 33955461
DOI: 10.1042/EBC20200139 -
Microbial Cell Factories Feb 2019Citric acid is the world's largest consumed organic acid and is widely used in beverage, food and pharmaceutical industries. Aspergillus niger is the main industrial... (Review)
Review
Citric acid is the world's largest consumed organic acid and is widely used in beverage, food and pharmaceutical industries. Aspergillus niger is the main industrial workhorse for citric acid production. Since the release of the genome sequence, extensive multi-omic data are being rapidly obtained, which greatly boost our understanding of the citric acid accumulation mechanism in A. niger to a molecular and system level. Most recently, the rapid development of CRISPR/Cas9 system facilitates highly efficient genome-scale genetic perturbation in A. niger. In this review, we summarize the impact of systems biology on the citric acid molecular regulatory mechanisms, the advances in metabolic engineering strategies for enhancing citric acid production and discuss the development and application of CRISPR/Cas9 systems for genome editing in A. niger. We believe that future systems metabolic engineering efforts will redesign and engineer A. niger as a highly optimized cell factory for industrial citric acid production.
Topics: Aspergillus niger; CRISPR-Cas Systems; Citric Acid; Gene Editing; Genome, Fungal; Genomics; Industrial Microbiology; Metabolic Engineering; Systems Biology
PubMed: 30717739
DOI: 10.1186/s12934-019-1064-6 -
MicrobiologyOpen Jan 2020The knowledge of how Aspergillus niger responds to ethanol can lead to the design of strains with enhanced ethanol tolerance to be utilized in numerous industrial...
The knowledge of how Aspergillus niger responds to ethanol can lead to the design of strains with enhanced ethanol tolerance to be utilized in numerous industrial bioprocesses. However, the current understanding about the response mechanisms of A. niger toward ethanol stress remains quite limited. Here, we first applied a cell growth assay to test the ethanol tolerance of A. niger strain ES4, which was isolated from the wall near a chimney of an ethanol tank of a petroleum company, and found that it was capable of growing in 5% (v/v) ethanol to 30% of the ethanol-free control level. Subsequently, the metabolic responses of this strain toward ethanol were investigated using untargeted metabolomics, which revealed the elevated levels of triacylglycerol (TAG) in the extracellular components, and of diacylglycerol, TAG, and hydroxy-TAG in the intracellular components. Lastly, stable isotope labeling mass spectrometry with ethanol-d showed altered isotopic patterns of molecular ions of lipids in the ethanol-d samples, compared with the nonlabeled ethanol controls, suggesting the ability of A. niger ES4 to utilize ethanol as a carbon source. Together, the studies revealed the upregulation of glycerolipid metabolism and ethanol utilization pathway as novel response mechanisms of A. niger ES4 toward ethanol stress, thereby underlining the utility of untargeted metabolomics and the overall approaches as tools for elucidating new biological insights.
Topics: Aspergillus niger; Diglycerides; Ethanol; Glycolipids; Metabolomics; Triglycerides
PubMed: 31646764
DOI: 10.1002/mbo3.948 -
Applied Biochemistry and Biotechnology May 2019In this study, acorn starch was investigated as a new material for fermenting production of citric acid by using a tannin tolerance mutant strain Aspergillus niger... (Review)
Review
In this study, acorn starch was investigated as a new material for fermenting production of citric acid by using a tannin tolerance mutant strain Aspergillus niger AA120. The mutant A. niger AA120 was obtained by initially atmospheric pressure plasma at room temperature (ARTP) mutagenesis and then tannin gradient domestication. ARTP experiments showed that a "double-saddle" shape of survival rate curve was achieved, and a positive mutation rate of 63.6% was reached by setting the implantation time of mutagenesis to 100 s. In contrast to the original stain at the presence of 20.0 g/L tannin in the medium, the selected mutant A. niger AA120 exhibits an increase of biomass by 43.76% to 32.9 g/L, and citric acid production capacity by 20.34% to 130.8 g/L, with 8% (w/w) of inoculation quantity, an initial pH of 6.2 and shaking speed of 250 r/min. In this work, we present a referable method for the mutagenesis screening of the A. niger, and the application of acorn starch as a new raw material for the development of the citric acid industry.
Topics: Adaptation, Physiological; Aspergillus niger; Atmospheric Pressure; Biomass; Citric Acid; Fermentation; Mutation; Nuts; Starch; Tannins; Temperature
PubMed: 30284209
DOI: 10.1007/s12010-018-2902-4 -
Medical Mycology Sep 2006Aspergillus niger is a filamentous ascomycete fungus that is ubiquitous in the environment and has been implicated in opportunistic infections of humans. In addition to... (Review)
Review
Aspergillus niger is a filamentous ascomycete fungus that is ubiquitous in the environment and has been implicated in opportunistic infections of humans. In addition to its role as an opportunistic human pathogen, A. niger is economically important as a fermentation organism used for the production of citric acid. Industrial citric acid production by A. niger represents one of the most efficient, highest yield bioprocesses in use currently by industry. The genome size of A. niger is estimated to be between 35.5 and 38.5 megabases (Mb) divided among eight chromosomes/linkage groups that vary in size from 3.5-6.6 Mb. Currently, there are three independent A. niger genome projects, an indication of the economic importance of this organism. The rich amount of data resulting from these multiple A. niger genome sequences will be used for basic and applied research programs applicable to fermentation process development, morphology and pathogenicity.
Topics: Aspergillus niger; Chromosomes, Fungal; DNA, Fungal; Fungal Proteins; Genome, Fungal; Genomics
PubMed: 17050415
DOI: 10.1080/13693780600921037 -
Applied Microbiology and Biotechnology May 2003This Mini-Review summarizes the current knowledge on the biochemical and physiological events leading to massive citric acid accumulation by Aspergillus niger under... (Review)
Review
This Mini-Review summarizes the current knowledge on the biochemical and physiological events leading to massive citric acid accumulation by Aspergillus niger under industrially comparable conditions, thereby particularly emphasizing the roles of glycolytic flux and its control, excretion of citric acid from the mitochondria and the cytosol, and the critical fermentation variables. The potential of novel techniques for metabolic analysis and genomic approaches in understanding this fermentation is also discussed.
Topics: Aspergillus niger; Carbon; Citric Acid; Cytosol; Fermentation; Mitochondria
PubMed: 12698275
DOI: 10.1007/s00253-002-1201-7 -
Applied Biochemistry and Biotechnology Jun 2015Steroids are derivatives of the triterpenoid squalene, containing three fused cyclohexane rings and a cyclopentane ring, and flavonoids are derivatives of... (Review)
Review
Steroids are derivatives of the triterpenoid squalene, containing three fused cyclohexane rings and a cyclopentane ring, and flavonoids are derivatives of L-phenylalanine, containing two aromatic rings joined by a three-carbon bridge that may form part of a heterocyclic ring. A great variety of steroids and flavonoids are produced by plants, and many additional steroids are produced by animals or fungi. Because these compounds have many nutritional and pharmaceutical values, and many of them cannot be produced by chemical synthesis, biotechnological processes are being developed that use cultures of Aspergillus niger and other fungi to transform steroids and flavonoids to a variety of metabolites. These biochemical reactions, including hydroxylation, dehydrogenation, O-methylation, demethylation, cleavage of rings, epoxide hydrolysis, double bond reduction, and others, may be used for the production of higher-value compounds.
Topics: Animals; Aspergillus niger; Biotransformation; Culture Techniques; Flavonoids; Humans; Steroids
PubMed: 25951777
DOI: 10.1007/s12010-015-1619-x -
FEMS Microbiology Letters Apr 2019Currently, there is no consensus regarding the mechanism underlying Aspergillus niger citrate biosynthesis and secretion. We hypothesise that depending on the... (Comparative Study)
Comparative Study
Currently, there is no consensus regarding the mechanism underlying Aspergillus niger citrate biosynthesis and secretion. We hypothesise that depending on the experimental setup, extracellular citrate accumulation can have fundamentally different underlying transcriptomic landscapes. We show that varying the amount and type of supplement of an arginine auxotrophic A. niger strain results in transcriptional down-regulation of citrate metabolising enzymes in the condition in which more citrate is accumulated extracellularly. This contrasts with the transcriptional adaptations when increased citrate production is triggered by iron limitation. By combining gene expression data obtained from these two very distinct experimental setups with hidden Markov models and transporter homology approaches, we were able to compile a shortlist of the most likely citrate transporter candidates. Two candidates (An17g01710 and An09g06720m.01) were heterologously expressed in the yeast Saccharomyces cerevisiae, and one of the resultant mutants showed the ability to secrete citrate. Our findings provide steps in untangling the complex interplay of different mechanisms underlying A. niger citrate accumulation, and we demonstrate how a comparative transcriptomics approach complemented with further bioinformatics analyses can be used to pinpoint a fungal citrate exporter.
Topics: Aspergillus niger; Carrier Proteins; Citric Acid; Fungal Proteins; Transcriptome
PubMed: 31062025
DOI: 10.1093/femsle/fnz071 -
Journal of Applied Microbiology Mar 2020To create an Aspergillus niger mutant with increased tolerance against ferulic acid using evolutionary adaptation.
AIMS
To create an Aspergillus niger mutant with increased tolerance against ferulic acid using evolutionary adaptation.
METHODS AND RESULTS
Evolutionary adaptation of A. niger N402 was performed by consecutive growth on increasing concentrations of ferulic acid in the presence of 25 mmol l d-fructose, starting from 0·5 mmol l and ending with 5 mmol l ferulic acid. The A. niger mutant obtained after six months, named Fa6, showed increased ferulic acid tolerance compared to the parent. In addition, Fa6 has increased ferulic acid consumption and a higher conversion rate, suggesting that the mutation affects aromatic metabolism of this species. Transcriptome analysis of the evolutionary mutant on ferulic acid revealed a distinct gene expression profile compared to the wild type. Further analysis of this mutant and the parent strain provided the first experimental confirmation that A. niger converts coniferyl alcohol to ferulic acid.
CONCLUSIONS
The evolutionary adaptive A. niger mutant Fa6 has beneficial mutations that increase the tolerance, conversion rate and uptake of ferulic acid.
SIGNIFICANCE AND IMPACT OF THE STUDY
This study demonstrates that evolutionary adaptation is a powerful tool to modify micro-organisms towards increased tolerance to harsh conditions, which is beneficial for various industrial applications.
Topics: Aspergillus niger; Coumaric Acids; Evolution, Molecular; Gene Expression Profiling; Mutation
PubMed: 31674709
DOI: 10.1111/jam.14505