Improving Organic Acid Secretion of <i>Aspergillus niger</i> by Overexpression C4-Dicarboxylic Acid Transporters
C4-dicarboxylic acids are essential organic compounds characterized by a four-carbon structure and two carboxyl groups. Their export from cells is mediated by specialized transporter proteins known as C4-dicarboxylic acid transporters (DCTs). The objective of this study was to investigate the specif...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-03-01
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| Series: | Fermentation |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2311-5637/11/3/156 |
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| Summary: | C4-dicarboxylic acids are essential organic compounds characterized by a four-carbon structure and two carboxyl groups. Their export from cells is mediated by specialized transporter proteins known as C4-dicarboxylic acid transporters (DCTs). The objective of this study was to investigate the specificity of six DCTs (DCT1-5 and C4t318) from <i>Aspergillus niger</i> or <i>Aspergillus oryzae</i>, focusing on their role in different production strategies for C4-dicarboxylic acids. The results indicate that compared to the WT strain, overexpressing <i>dct</i>2 or <i>dct</i>3 in <i>A. niger</i> CGMCC NO. 40550 specifically enhances the production of succinic acid, increasing its yield from 5.69 g/L to 6.28 g/L, and L-malic acid, increasing its yield from 11.02 g/L to 12.11 g/L. Additionally, <i>dct</i>5 appears to be involved in the transport of both succinic acid (6.19 g/L) and L-malic acid (16.33 g/L). The total acid yields of T-D3-7, which lacks the oxaloacetate hydrolase gene, were improved to 27.75 g/L, compared to 25.19 g/L for T-D3-26, due to blocking the branch of oxaloacetate metabolism. Furthermore, the heterologous expression of <i>A. oryzae</i> C4T318 in <i>A. niger</i> increased the production of L-malic acid by approximately 22.5%. Furthermore, the best results were observed when the strains T-D3-7 and T-D5-16 were scaled up in a 30 L bioreactor for 84 h. The succinic acid and L-malic acid yields of T-D3-7 and T-D5-16 reached 14.51 g/L and 70.79 g/L or 41.59 g/L and 81.08 g/L, respectively. Moreover, the purity of L-malic acid produced by T-D3-7 reached 71%. This work further clarifies the specificity of C4-dicarboxylic acid transporters and provides valuable insights for optimizing organic acid production. |
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| ISSN: | 2311-5637 |