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Li M, Chu Y, Dong X, Ji H. General mechanisms of weak acid-tolerance and current strategies for the development of tolerant yeasts. World J Microbiol Biotechnol 2023; 40:49. [PMID: 38133718 DOI: 10.1007/s11274-023-03875-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 12/16/2023] [Indexed: 12/23/2023]
Abstract
Yeast cells are often subjected to various types of weak acid stress in the process of industrial production, food processing, and preservation, resulting in growth inhibition and reduced fermentation performance. Under acidic conditions, weak acids enter the near-neutral yeast cytoplasm and dissociate into protons and anions, leading to cytoplasmic acidification and cell damage. Although some yeast strains have developed the ability to survive weak acids, the complexity and diversity of stresses during industrial production still require the application of appropriate strategies for phenotypes improvement. In this review, we summarized current knowledge concerning weak acid stress response and resistance, which may suggest important targets for further construction of more robust strains. We also highlight current feasible strategies for improving the weak acid resistance of yeasts, such as adaptive laboratory evolution, transcription factors engineering, and cell membrane/wall engineering. Moreover, the challenges and perspectives associated with improving the competitiveness of industrial strains are also discussed. This review provides effective strategies for improving the industrial phenotypes of yeast from multiple dimensions in future studies.
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Affiliation(s)
- Mengmeng Li
- Institute of Life Sciences, College of Life and Environmental Science, Wenzhou University, Wenzhou, Zhejiang, 325035, PR China
- Biomedical Collaborative Innovation Center of Zhejiang Province & Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Wenzhou University, Wenzhou, Zhejiang, 325035, PR China
| | - Yunfei Chu
- Institute of Life Sciences, College of Life and Environmental Science, Wenzhou University, Wenzhou, Zhejiang, 325035, PR China
- Biomedical Collaborative Innovation Center of Zhejiang Province & Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Wenzhou University, Wenzhou, Zhejiang, 325035, PR China
| | - Xiameng Dong
- Department of Agriculture and Biotechnology, Wenzhou Vocational College of Science and Technology, Wenzhou, Zhejiang, 325006, PR China.
| | - Hao Ji
- Institute of Life Sciences, College of Life and Environmental Science, Wenzhou University, Wenzhou, Zhejiang, 325035, PR China.
- Biomedical Collaborative Innovation Center of Zhejiang Province & Engineering Laboratory of Zhejiang Province for Pharmaceutical Development of Growth Factors, Wenzhou University, Wenzhou, Zhejiang, 325035, PR China.
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Alves J, Sousa-Silva M, Soares P, Sauer M, Casal M, Soares-Silva I. Structural characterization of the Aspergillus niger citrate transporter CexA uncovers the role of key residues S75, R192 and Q196. Comput Struct Biotechnol J 2023; 21:2884-2898. [PMID: 37216016 PMCID: PMC10196274 DOI: 10.1016/j.csbj.2023.04.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 04/25/2023] [Accepted: 04/25/2023] [Indexed: 05/24/2023] Open
Abstract
The Aspergillus niger CexA transporter belongs to the DHA1 (Drug-H+ antiporter) family. CexA homologs are exclusively found in eukaryotic genomes, and CexA is the sole citrate exporter to have been functionally characterized in this family so far. In the present work, we expressed CexA in Saccharomyces cerevisiae, demonstrating its ability to bind isocitric acid, and import citrate at pH 5.5 with low affinity. Citrate uptake was independent of the proton motive force and compatible with a facilitated diffusion mechanism. To unravel the structural features of this transporter, we then targeted 21 CexA residues for site-directed mutagenesis. Residues were identified by a combination of amino acid residue conservation among the DHA1 family, 3D structure prediction, and substrate molecular docking analysis. S. cerevisiae cells expressing this library of CexA mutant alleles were evaluated for their capacity to grow on carboxylic acid-containing media and transport of radiolabeled citrate. We also determined protein subcellular localization by GFP tagging, with seven amino acid substitutions affecting CexA protein expression at the plasma membrane. The substitutions P200A, Y307A, S315A, and R461A displayed loss-of-function phenotypes. The majority of the substitutions affected citrate binding and translocation. The S75 residue had no impact on citrate export but affected its import, as the substitution for alanine increased the affinity of the transporter for citrate. Conversely, expression of CexA mutant alleles in the Yarrowia lipolytica cex1Δ strain revealed the involvement of R192 and Q196 residues in citrate export. Globally, we uncovered a set of relevant amino acid residues involved in CexA expression, export capacity and import affinity.
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Affiliation(s)
- J. Alves
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - M. Sousa-Silva
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - P. Soares
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - M. Sauer
- University of Natural Resources and Life Sciences, Vienna, Department of Biotechnology, Institute of Microbiology and Microbial Biotechnology, Muthgasse 18, 1190 Vienna, Austria
- Austrian Centre of Industrial Biotechnology (ACIB GmbH), Muthgasse 11, 1190 Vienna, Austria
| | - M. Casal
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - I. Soares-Silva
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Institute of Science and Innovation for Bio-Sustainability (IB-S), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
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The Dicarboxylate Transporters from the AceTr Family and Dct-02 Oppositely Affect Succinic Acid Production in S. cerevisiae. J Fungi (Basel) 2022; 8:jof8080822. [PMID: 36012810 PMCID: PMC9409672 DOI: 10.3390/jof8080822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/28/2022] [Accepted: 08/04/2022] [Indexed: 11/17/2022] Open
Abstract
Membrane transporters are important targets in metabolic engineering to establish and improve the production of chemicals such as succinic acid from renewable resources by microbial cell factories. We recently provided a Saccharomyces cerevisiae strain able to strongly overproduce succinic acid from glycerol and CO2 in which the Dct-02 transporter from Aspergillus niger, assumed to be an anion channel, was used to export succinic acid from the cells. In a different study, we reported a new group of succinic acid transporters from the AceTr family, which were also described as anion channels. Here, we expressed these transporters in a succinic acid overproducing strain and compared their impact on extracellular succinic acid accumulation with that of the Dct-02 transporter. The results show that the tested transporters of the AceTr family hinder succinic acid accumulation in the extracellular medium at low pH, which is in strong contrast to Dct-02. Data suggests that the AceTr transporters prefer monovalent succinate, whereas Dct-02 prefers divalent succinate anions. In addition, the results provided deeper insights into the characteristics of Dct-02, showing its ability to act as a succinic acid importer (thus being bidirectional) and verifying its capability of exporting malate.
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