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Deletion of glucose oxidase changes the pattern of organic acid production in Aspergillus carbonarius.

Yang L, Lübeck M, Lübeck PS - AMB Express (2014)

Bottom Line: Aspergillus carbonarius has potential as a cell factory for the production of different organic acids.The effect of genetic engineering was examined by testing glucose oxidase deficient (Δgox) mutants for the production of different organic acids in a defined production medium.The results obtained showed that the gluconic acid accumulation was completely inhibited and increased amounts of citric acid, oxalic acid and malic acid were observed in the Δgox mutants.

View Article: PubMed Central - HTML - PubMed

Affiliation: Section for Sustainable Biotechnology, Aalborg University Copenhagen, A. C. Meyers Vænge 15, Copenhagen, DK-2450, SV, Denmark.

ABSTRACT
Aspergillus carbonarius has potential as a cell factory for the production of different organic acids. At pH 5.5, A.carbonarius accumulates high amounts of gluconic acid when it grows on glucose based medium whereas at low pH, it produces citric acid. The conversion of glucose to gluconic acid is carried out by secretion of the enzyme, glucose oxidase. In this work, the gene encoding glucose oxidase was identified and deleted from A. carbonarius with the aim of changing the carbon flux towards other organic acids. The effect of genetic engineering was examined by testing glucose oxidase deficient (Δgox) mutants for the production of different organic acids in a defined production medium. The results obtained showed that the gluconic acid accumulation was completely inhibited and increased amounts of citric acid, oxalic acid and malic acid were observed in the Δgox mutants.

No MeSH data available.


The effect of gene deletion on the production of organic acids byA. carbonarius.(a) The concentration of citric acid in the fermentation medium after day 3 and 7 (b) The concentration of oxalic acid in the fermentation medium after day 3 and 7 (c) The concentration of malic acid in the fermentation medium after day 7.
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Figure 4: The effect of gene deletion on the production of organic acids byA. carbonarius.(a) The concentration of citric acid in the fermentation medium after day 3 and 7 (b) The concentration of oxalic acid in the fermentation medium after day 3 and 7 (c) The concentration of malic acid in the fermentation medium after day 7.

Mentions: Cultivation with the selected Δgox mutants was carried out in shaking flasks at pH 5.5 to investigate the effect of the gox gene deletion on production of organic acids in A. carbonarius. However, due to the accumulation and consumption of gluconic acid by wild type A. carbonarius, it is difficult to use glucose as the sole carbon source to compare the performance of wild-type strain with the Δgox mutant during growth. The evaluation of organic acid production was carried out based on the concentration of extracellular acid products in the cultivation broth. As shown in Figure 4a, the concentration of citric acid was dramatically increased after 7 days cultivation in the Δgox mutants compared with the wild type 5010 and the parent KB1039 (ΔkusA) strains. In addition, an accumulation of oxalic acid was also observed in the Δgox mutants during the cultivation (Figure 4b) and the production of malic acid also increased 2.4 and 1.8 folds, respectively, compared with the parent strain and the wild type strain (Figure 4c).


Deletion of glucose oxidase changes the pattern of organic acid production in Aspergillus carbonarius.

Yang L, Lübeck M, Lübeck PS - AMB Express (2014)

The effect of gene deletion on the production of organic acids byA. carbonarius.(a) The concentration of citric acid in the fermentation medium after day 3 and 7 (b) The concentration of oxalic acid in the fermentation medium after day 3 and 7 (c) The concentration of malic acid in the fermentation medium after day 7.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230901&req=5

Figure 4: The effect of gene deletion on the production of organic acids byA. carbonarius.(a) The concentration of citric acid in the fermentation medium after day 3 and 7 (b) The concentration of oxalic acid in the fermentation medium after day 3 and 7 (c) The concentration of malic acid in the fermentation medium after day 7.
Mentions: Cultivation with the selected Δgox mutants was carried out in shaking flasks at pH 5.5 to investigate the effect of the gox gene deletion on production of organic acids in A. carbonarius. However, due to the accumulation and consumption of gluconic acid by wild type A. carbonarius, it is difficult to use glucose as the sole carbon source to compare the performance of wild-type strain with the Δgox mutant during growth. The evaluation of organic acid production was carried out based on the concentration of extracellular acid products in the cultivation broth. As shown in Figure 4a, the concentration of citric acid was dramatically increased after 7 days cultivation in the Δgox mutants compared with the wild type 5010 and the parent KB1039 (ΔkusA) strains. In addition, an accumulation of oxalic acid was also observed in the Δgox mutants during the cultivation (Figure 4b) and the production of malic acid also increased 2.4 and 1.8 folds, respectively, compared with the parent strain and the wild type strain (Figure 4c).

Bottom Line: Aspergillus carbonarius has potential as a cell factory for the production of different organic acids.The effect of genetic engineering was examined by testing glucose oxidase deficient (Δgox) mutants for the production of different organic acids in a defined production medium.The results obtained showed that the gluconic acid accumulation was completely inhibited and increased amounts of citric acid, oxalic acid and malic acid were observed in the Δgox mutants.

View Article: PubMed Central - HTML - PubMed

Affiliation: Section for Sustainable Biotechnology, Aalborg University Copenhagen, A. C. Meyers Vænge 15, Copenhagen, DK-2450, SV, Denmark.

ABSTRACT
Aspergillus carbonarius has potential as a cell factory for the production of different organic acids. At pH 5.5, A.carbonarius accumulates high amounts of gluconic acid when it grows on glucose based medium whereas at low pH, it produces citric acid. The conversion of glucose to gluconic acid is carried out by secretion of the enzyme, glucose oxidase. In this work, the gene encoding glucose oxidase was identified and deleted from A. carbonarius with the aim of changing the carbon flux towards other organic acids. The effect of genetic engineering was examined by testing glucose oxidase deficient (Δgox) mutants for the production of different organic acids in a defined production medium. The results obtained showed that the gluconic acid accumulation was completely inhibited and increased amounts of citric acid, oxalic acid and malic acid were observed in the Δgox mutants.

No MeSH data available.