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Proteome analysis of Aspergillus niger: lactate added in starch-containing medium can increase production of the mycotoxin fumonisin B2 by modifying acetyl-CoA metabolism.

ABSTRACT: BACKGROUND:Aspergillus niger is a filamentous fungus found in the environment, on foods and feeds and is used as host for production of organic acids, enzymes and proteins. The mycotoxin fumonisin B2 was recently found to be produced by A. niger and hence very little is known about production and regulation of this metabolite. Proteome analysis was used with the purpose to reveal how fumonisin B2 production by A. niger is influenced by starch and lactate in the medium. RESULTS:Fumonisin B2 production by A. niger was significantly increased when lactate and starch were combined in the medium. Production of a few other A. niger secondary metabolites was affected similarly by lactate and starch (fumonisin B4, orlandin, desmethylkotanin and pyranonigrin A), while production of others was not (ochratoxin A, ochratoxin alpha, malformin A, malformin C, kotanin, aurasperone B and tensidol B). The proteome of A. niger was clearly different during growth on media containing 3% starch, 3% starch + 3% lactate or 3% lactate. The identity of 59 spots was obtained, mainly those showing higher or lower expression levels on medium with starch and lactate. Many of them were enzymes in primary metabolism and other processes that affect the intracellular level of acetyl-CoA or NADPH. This included enzymes in the pentose phosphate pathway, pyruvate metabolism, the tricarboxylic acid cycle, ammonium assimilation, fatty acid biosynthesis and oxidative stress protection. CONCLUSIONS:Lactate added in a medium containing nitrate and starch can increase fumonisin B2 production by A. niger as well as production of some other secondary metabolites. Changes in the balance of intracellular metabolites towards a higher level of carbon passing through acetyl-CoA and a high capacity to regenerate NADPH during growth on medium with starch and lactate were found to be the likely cause of this effect. The results lead to the hypothesis that fumonisin production by A. niger is regulated by acetyl-CoA.

SUBMITTER: Sorensen LM

PROVIDER: S-EPMC2807875 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Proteome analysis of Aspergillus niger: lactate added in starch-containing medium can increase production of the mycotoxin fumonisin B2 by modifying acetyl-CoA metabolism.

Sørensen Louise M LM Lametsch Rene R Andersen Mikael R MR Nielsen Per V PV Frisvad Jens C JC

BMC microbiology 20091210

<h4>Background</h4>Aspergillus niger is a filamentous fungus found in the environment, on foods and feeds and is used as host for production of organic acids, enzymes and proteins. The mycotoxin fumonisin B2 was recently found to be produced by A. niger and hence very little is known about production and regulation of this metabolite. Proteome analysis was used with the purpose to reveal how fumonisin B2 production by A. niger is influenced by starch and lactate in the medium.<h4>Results</h4>Fum ...[more]

PMID: 20003296

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Project description:Cytosolic acetyl-coenzyme A is a precursor for many biotechnologically relevant compounds produced by Saccharomyces cerevisiae. In this yeast, cytosolic acetyl-CoA synthesis and growth strictly depend on expression of either the Acs1 or Acs2 isoenzyme of acetyl-CoA synthetase (ACS). Since hydrolysis of ATP to AMP and pyrophosphate in the ACS reaction constrains maximum yields of acetyl-CoA-derived products, this study explores replacement of ACS by two ATP-independent pathways for acetyl-CoA synthesis. After evaluating expression of different bacterial genes encoding acetylating acetaldehyde dehydrogenase (A-ALD) and pyruvate-formate lyase (PFL), acs1M-NM-^T acs2M-NM-^T S. cerevisiae strains were constructed in which A-ALD or PFL successfully replaced ACS. In A-ALD-dependent strains, aerobic growth rates of up to 0.27 h-1 were observed, while anaerobic growth rates of PFL-dependent S. cerevisiae (0.21 h-1) were stoichiometrically coupled to formate production. In glucose-limited chemostat cultures, intracellular metabolite analysis did not reveal major differences between A-ALD-dependent and reference strains. However, biomass yields on glucose of A-ALD- and PFL-dependent strains were lower than those of the reference strain. Transcriptome analysis suggested that reduced biomass yields were caused by acetaldehyde and formate in A-ALD- and PFL-dependent strains, respectively. Transcript profiles also indicated that a previously proposed role of Acs2 in histone acetylation is probably linked to cytosolic acetyl-CoA levels rather than to direct involvement of Acs2 in histone acetylation. While, for the first time, demonstrating that yeast ACS can be fully replaced by alternative reactions, this study demonstrates that further modifications are needed to achieve optimal in vivo efficiencies of the supply of acetyl-CoA as product precursor. To investigate the impact of introduced changes in native pathway of cytosolic acetyl-CoA formation in S. cerevisiae, a DNA microarray-based transcriptome analysis was performed on aerobic or anaerobic, glucose-limited chemostat cultures.

Dataset Information

Proteome analysis of Aspergillus niger: lactate added in starch-containing medium can increase production of the mycotoxin fumonisin B2 by modifying acetyl-CoA metabolism.

Publications

Proteome analysis of Aspergillus niger: lactate added in starch-containing medium can increase production of the mycotoxin fumonisin B2 by modifying acetyl-CoA metabolism.

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