Enhanced citrate production through gene insertion in Aspergillus niger
1Center for Microbial Biotechnology, Technical University of Denmark, Søltofts Plads, Bygning 223, DK-2800 Kgs. Lyngby, Denmark.
Metabolic Engineering
|December 29, 2007
Summary
Genetic modification of Aspergillus niger enhanced citrate production by introducing genes from the tricarboxylic acid cycle. Engineered strains produced more citrate, even in manganese-contaminated environments.
Area of Science:
- Biotechnology
- Metabolic Engineering
- Industrial Microbiology
Background:
- Citrate production is a key industrial bioprocess.
- The tricarboxylic acid (TCA) cycle is central to cellular metabolism.
- Modulating TCA cycle genes can impact metabolite yields.
Purpose of the Study:
- To investigate the impact of introducing genes from the reductive TCA cycle on citrate production in Aspergillus niger.
- To evaluate the performance of engineered strains under challenging conditions, such as manganese contamination.
Main Methods:
- Genetic engineering of Aspergillus niger by inserting genes encoding malate dehydrogenase (mdh2), fumarases (Fum1s, FumRs), and fumarate reductase (Frds1).
- Fermentation studies to compare citrate yield and productivity of transformant strains against the wild-type.
- Analysis of citrate production in the presence of trace manganese.
Main Results:
- All engineered Aspergillus niger strains exhibited enhanced citrate yield and productivity compared to the wild-type.
- Transformants could produce citrate in trace-manganese-contaminated media, unlike the wild-type.
- Overexpression of FumRs and Frds1 yielded the most effective strain, achieving 0.9g citrate/g glucose and 0.025g citrate/g DW/h.
Conclusions:
- Engineering the reductive branch of the TCA cycle is a viable strategy to improve citrate production in Aspergillus niger.
- The modified strains demonstrate robustness and enhanced performance in the presence of manganese contamination.
- Specific gene combinations, such as FumRs and Frds1, show significant potential for industrial-scale citrate biosynthesis.
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