Citrate transport during the citric acid fermentation by Aspergillus niger

Kontopidis, George; Mattey, Michael; Kristiansen, B.

doi:10.1007/bf00143110

Cited by 10 publications

(4 citation statements)

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“…Because a dramatic pH gradient exists between the plasma and the extracellular medium, citrate is produced mainly as citrate 2− in the cytosol (with a pH between 6.0 and 7.0) and as an undissociated form of acid in medium (with a pH below 2.0)56. Citrate 2− can be secreted from A. niger into broth, and the hyphae can take up citrate at the end of citrate fermentation, which indicates that both of the 2 forms of citrate can cross the cell wall.…”

Section: Resultsmentioning

confidence: 99%

Comparative genomics and transcriptome analysis of Aspergillus niger and metabolic engineering for citrate production

Yin

Shin

et al. 2017

Sci Rep

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Despite a long and successful history of citrate production in Aspergillus niger, the molecular mechanism of citrate accumulation is only partially understood. In this study, we used comparative genomics and transcriptome analysis of citrate-producing strains-namely, A. niger H915-1 (citrate titer: 157 g L −1 ), A1 (117 g L −1 ), and L2 (76 g L −1 )-to gain a genome-wide view of the mechanism of citrate accumulation. Compared with A. niger A1 and L2, A. niger H915-1 contained 92 mutated genes, including a succinatesemialdehyde dehydrogenase in the γ-aminobutyric acid shunt pathway and an aconitase family protein involved in citrate synthesis. Furthermore, transcriptome analysis of A. niger H915-1 revealed that the transcription levels of 479 genes changed between the cell growth stage (6 h) and the citrate synthesis stage (12 h, 24 h, 36 h, and 48 h). In the glycolysis pathway, triosephosphate isomerase was up-regulated, whereas pyruvate kinase was down-regulated. Two cytosol ATP-citrate lyases, which take part in the cycle of citrate synthesis, were up-regulated, and may coordinate with the alternative oxidases in the alternative respiratory pathway for energy balance. Finally, deletion of the oxaloacetate acetylhydrolase gene in H915-1 eliminated oxalate formation but neither influence on pH decrease nor difference in citrate production were observed.Aspergillus niger, a black aspergillus with "generally regarded as safe" status, is widely used in the biotechnological production of organic acids and industrial enzymes 1 . As a workhorse of organic acids, A. niger is a proficient producer of citrate, which is used extensively in the food and pharmaceutical industries owing to its safety, pleasant acidic taste, high water solubility, and chelating properties 2 .If A. niger is to be used as a cell factory platform, its genetic background must be thoroughly understood. The available genome sequence of A. niger offers a new horizon for both scientific studies and biotechnological applications 3 . A. niger strains NRRL 3 and ATCC 1015, which can synthesize citrate, have undergone genome-wide analysis 1,3 , and a complete genome-scale metabolic model with genomic annotation has been constructed based on the genome sequence of A. niger ATCC 1015 4 . Nevertheless, the molecular mechanism of citrate accumulation remains only partially understood 5,6 . For example, 5 citrate synthases have been identified in ATCC 9029 7 ; however, the primary gene and the timing of the activity of each enzyme during fermentation remain a mystery. Furthermore, the citrate transporter remains unknown even though the transport process is critical in the production of citrate. In addition, the role of alternative oxidases for energy balance during citrate production must be clarified 8 .In this study, the genomes of three A. niger strains with different citrate production efficiencies were sequenced, among which the genome of industrial strain A. niger H915-1 was sequenced with third-generation sequencing, which provides much longer reads an...

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Section: Resultsmentioning

confidence: 99%

Comparative genomics and transcriptome analysis of Aspergillus niger and metabolic engineering for citrate production

Yin

Shin

et al. 2017

Sci Rep

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“…14) Moreover, de Jongh and Nielsen pointed out the importance of the organic acids transport system between mitochondria and cytosol by gene insertion. 15) However, there are only a few reports on exporting citric acid from the cytosol to the external medium, 16,17) and less is known about the transport system, especially the system for exporting citric acid from mitochondria to the cytosol.…”

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confidence: 99%

Phenotypes of gene disruptants in relation to a putative mitochondrial malate–citrate shuttle protein in citric acid-producing Aspergillus niger

Kirimura

Kobayashi

Ueda

et al. 2016

Bioscience, Biotechnology, and Biochemistry

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The mitochondrial citrate transport protein (CTP) functions as a malate-citrate shuttle catalyzing the exchange of citrate plus a proton for malate between mitochondria and cytosol across the inner mitochondrial membrane in higher eukaryotic organisms. In this study, for functional analysis, we cloned the gene encoding putative CTP (ctpA) of citric acid-producing Aspergillus niger WU-2223L. The gene ctpA encodes a polypeptide consisting 296 amino acids conserved active residues required for citrate transport function. Only in early-log phase, the ctpA disruptant DCTPA-1 showed growth delay, and the amount of citric acid produced by strain DCTPA-1 was smaller than that by parental strain WU-2223L. These results indicate that the CTPA affects growth and thereby citric acid metabolism of A. niger changes, especially in early-log phase, but not citric acid-producing period. This is the first report showing that disruption of ctpA causes changes of phenotypes in relation to citric acid production in A. niger.

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“…Another explanation for the effect of manganese ion deficiency on the accumulation of citric acid was the necessity to avoid the re-uptake of citrate that would obviously decrease external accumulation. Uptake of citrate in the production phase of the fermentation was indeed shown for A. niger [74]. Since manganese-chelated citrate can be imported by A. niger cells, by preventing the formation of manganese-citrate complexes, re-uptake can be averted and a higher productivity be obtained [75].…”

Section: Biochemical and Physiological Interpretations Of The Roles Of Manganese Ions On Citric And Itaconic Acid Accumulationmentioning

confidence: 78%

The Role of Metal Ions in Fungal Organic Acid Accumulation

2021

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Organic acid accumulation is probably the best-known example of primary metabolic overflow. Both bacteria and fungi are capable of producing various organic acids in large amounts under certain conditions, but in terms of productivity-and consequently, of commercial importance-fungal platforms are unparalleled. For high product yield, chemical composition of the growth medium is crucial in providing the necessary conditions, of which the concentrations of four of the first-row transition metal elements, manganese (Mn2+), iron (Fe2+), copper (Cu2+) and zinc (Zn2+) stand out. In this paper we critically review the biological roles of these ions, the possible biochemical and physiological consequences of their influence on the accumulation of the most important mono-, di- and tricarboxylic as well as sugar acids by fungi, and the metal ion-related aspects of submerged organic acid fermentations, including the necessary instrumental analytics. Since producing conditions are associated with a cell physiology that differs strongly to what is observed under “standard” growth conditions, here we consider papers and patents only in which organic acid accumulation levels achieved at least 60% of the theoretical maximum yield, and the actual trace metal ion concentrations were verified.

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Citrate transport during the citric acid fermentation by Aspergillus niger

Cited by 10 publications

References 10 publications

Comparative genomics and transcriptome analysis of Aspergillus niger and metabolic engineering for citrate production

Comparative genomics and transcriptome analysis of Aspergillus niger and metabolic engineering for citrate production

Phenotypes of gene disruptants in relation to a putative mitochondrial malate–citrate shuttle protein in citric acid-producing Aspergillus niger

The Role of Metal Ions in Fungal Organic Acid Accumulation

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