![]() itaconic acid production by genetically altered A. Considerable research efforts have been taken to reveal the mechanism of citric acid accumulation by the fungus and to redirect carbon flux from the production of citric acid towards other types of organic acids, e.g. citric acid) from a broad range of substrates. niger is able to produce high amounts of organic acids (e.g. carbonarius, the roles of mitochondrial transport of organic acid have been investigated in more details. niger, which is phylogenetically related to A. In the well-known organic acid producer, A. Overexpression of the transporter led to a significant increase of C 4-dicarboxylic acid production and decreased citric acid production. Recently, we identified a plasma membrane C 4-dicarboxylate transporter, which was highly involved in the dicarboxylic acid production. malic acid is transported to the mitochondria in exchange with citric acid. This phenomenon might be a result of the transport of organic acids across the mitochondrial membrane where e.g. When several genetic modifications were made to improve carbon flux towards dicarboxylic acid production (fumaric, succinic and malic acid), an increased production of citric acid was often observed. Recently, Aspergillus carbonarius was reported to be an efficient organic acid producer and as such may have a potential for bio-based production of C4-dicarboxylic acids. malic acid and succinic acid) can easily be converted and used as building blocks for deriving different commodity and specialty chemicals and in the past decades, filamentous fungi as Aspergillus niger and Aspergillus oryzae have been used in industrial production of organic acids. filamentous fungi in a biorefinery has a high potential as a substitution of chemicals produced from crude oil. More extensive studies should be conducted in order to further reveal the mechanism of organic acid transport as mediated by the MtpA transporter.īio-based production of organic acids by microorganisms as e.g. The mtpA knockout strains obtained produced less citric acid and more malic acid than the wild type, in agreement with our original hypothesis. carbonarius was identified and further investigated on its effects on production of citric acid and malic acid. ConclusionĪ putative oxaloacetate transporter gene which is potentially involved in organic acid production by A. In total, 6 transformants with gene mtpA disrupted were obtained and they showed secretion of malic acid at the expense of citric acid production. To study its role in organic acid production, we disrupted the gene and analyzed its effects on production of citric acid and other organic acids, such as malic acid. carbonarius based on transcription analysis. This gene named mtpA encoding a putative oxaloacetate transport protein was expressed constitutively in A. In this work, we studied another citric acid producing fungus, Aspergillus carbonarius, and identified by genome-mining a putative mitochondrial transporter MtpA, which was not previously studied, that might be involved in production of citric acid. niger showing their effects on organic acid production. Several mitochondrial organic acid transporters were recently studied in A. In Aspergillus niger, accumulation of malate in the cytosol can trigger production of citric acid via the exchange of malate and citrate across the mitochondrial membrane. These transporters may transfer different organic acids across the membrane while taking others the opposite direction. In filamentous fungi, transport of organic acids across the mitochondrial membrane is facilitated by active transport via shuttle proteins.
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