scholarly journals Enhanced citric acid biosynthesis in Pseudomonas fluorescens ATCC 13525 by overexpression of the Escherichia coli citrate synthase gene

Microbiology ◽  
2009 ◽  
Vol 155 (8) ◽  
pp. 2620-2629 ◽  
Author(s):  
Aditi D. Buch ◽  
G. Archana ◽  
G. Naresh Kumar
Keyword(s):  
Escherichia Coli ◽  
Citric Acid ◽  
Acid Secretion ◽  
Pseudomonas Fluorescens ◽  
Phosphoenolpyruvate Carboxylase ◽  
Citrate Synthase ◽  
Acid Biosynthesis ◽  
Acid Yield ◽  
Glucose Catabolism ◽  
Citric Acid Biosynthesis

Citric acid secretion by fluorescent pseudomonads has a distinct significance in microbial phosphate solubilization. The role of citrate synthase in citric acid biosynthesis and glucose catabolism in pseudomonads was investigated by overexpressing the Escherichia coli citrate synthase (gltA) gene in Pseudomonas fluorescens ATCC 13525. The resultant ∼2-fold increase in citrate synthase activity in the gltA-overexpressing strain Pf(pAB7) enhanced the intracellular and extracellular citric acid yields during the stationary phase, by about 2- and 26-fold, respectively, as compared to the control, without affecting the growth rate, glucose depletion rate or biomass yield. Decreased glucose consumption was paralleled by increased gluconic acid production due to an increase in glucose dehydrogenase activity. While the extracellular acetic acid yield increased in Pf(pAB7), pyruvic acid secretion decreased, correlating with an increase in pyruvate carboxylase activity and suggesting an increased demand for the anabolic precursor oxaloacetate. Activities of two other key enzymes, glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase, remained unaltered, and the contribution of phosphoenolpyruvate carboxylase and isocitrate lyase to glucose catabolism was negligible. Strain Pf(pAB7) demonstrated an enhanced phosphate-solubilizing ability compared to the control. Co-expression of the Synechococcus elongatus PCC 6301 phosphoenolpyruvate carboxylase and E. coli gltA genes in P. fluorescens ATCC 13525, so as to supplement oxaloacetate for citrate biosynthesis, neither significantly affected citrate biosynthesis nor caused any change in the other physiological and biochemical parameters measured, despite approximately 1.3- and 5-fold increases in citrate synthase and phosphoenolpyruvate carboxylase activities, respectively. Thus, our results demonstrate that citrate synthase is rate-limiting in enhancing citrate biosynthesis in P. fluorescens ATCC 13525. Significantly low extracellular citrate levels as compared to the intracellular levels in Pf(pAB7) suggested a probable limitation of efficient citrate transport.

scholarly journals The effect of Aspergillus niger mutagenization on citric acid biosynthesis

2014 ◽  
Vol 27 (2) ◽  
pp. 225-230
Author(s):  
Stanisław Walisch ◽  
Krystyna Juda
Keyword(s):  
Citric Acid ◽  
Aspergillus Niger ◽  
Acid Production ◽  
Industrial Process ◽  
Nitroxyl Radicals ◽  
Initial Strain ◽  
Acid Biosynthesis ◽  
Chemical Mutagens ◽  
Free Nitroxyl Radicals ◽  
Citric Acid Biosynthesis

The industrial <i>A. niger</i> strain producing citric acid was mutagenized with the use of new chemical mutagens: free nitroxyl radicals. Strains of higher citric acid production yield were obtained. Citric acid was produced in a shorter time compared to the initial strain. During 6-12 months of storage most of the strains preserved their positive features which proves that mutants with profitable biotechnological properties were obtained. These mutants are used in industrial process.

Application of scale-down experiments in the study of citric acid biosynthesis

1991 ◽  
Vol 36 (5) ◽  
pp. 493-497 ◽  
Author(s):  
P. Ettler ◽  
L. Martínková ◽  
E. Ujcová ◽  
L. Seichert
Keyword(s):  
Citric Acid ◽  
Acid Biosynthesis ◽  
Scale Down ◽  
Citric Acid Biosynthesis

scholarly journals Changes in the Content of Organic Acids and Expression Analysis of Citric Acid Accumulation-Related Genes during Fruit Development of Yellow (Passiflora edulis f. flavicarpa) and Purple (Passiflora edulis f. edulis) Passion Fruits

2021 ◽  
Vol 22 (11) ◽  
pp. 5765
Author(s):  
Xiaoxue Zhang ◽  
Xiaoxia Wei ◽  
Muhammad Moaaz Ali ◽  
Hafiz Muhammad Rizwan ◽  
Binqi Li ◽  
...  
Keyword(s):  
Citric Acid ◽  
Organic Acids ◽  
Organic Acid ◽  
Fruit Development ◽  
Nutritive Value ◽  
Citrate Synthase ◽  
Passion Fruit ◽  
Mature Stage ◽  
Acid Biosynthesis ◽  
Passiflora Edulis

Organic acids are key components that determine the taste and flavor of fruits and play a vital role in maintaining fruit quality and nutritive value. In this study, the fruits of two cultivars of passion fruit Yellow (Passiflora edulis f. flavicarpa) and purple (Passiflora edulis f. edulis) were harvested at five different developmental stages (i.e., fruitlet, green, veraison, near-mature and mature stage) from an orchard located in subtropical region of Fujian Province, China. The contents of six organic acids were quantified using ultra-performance liquid chromatography (UPLC), activities of citric acid related enzymes were determined, and expression levels of genes involved in citric acid metabolism were measured by quantitative real-time PCR (qRT-PCR). The results revealed that citric acid was the predominant organic acid in both cultivars during fruit development. The highest citric acid contents were observed in both cultivars at green stage, which were reduced with fruit maturity. Correlation analysis showed that citrate synthase (CS), cytosolic aconitase (Cyt-ACO) and cytosolic isocitrate dehydrogenase (Cyt-IDH) may be involved in regulating citric acid biosynthesis. Meanwhile, the PeCS2, PeACO4, PeACO5 and PeIDH1 genes may play an important role in regulating the accumulation of citric acid. This study provides new insights for future elucidation of key mechanisms regulating organic acid biosynthesis in passion fruit.

Optimization of ammonium nitrate concentration in single-stage continuous cultures of Aspergillus niger with biomass retention

2007 ◽  
Vol 61 (3) ◽  
Author(s):  
M. Janczar ◽  
J. Pietkiewicz
Keyword(s):  
Citric Acid ◽  
Aspergillus Niger ◽  
Ammonium Nitrate ◽  
Nitrate Concentration ◽  
Single Stage ◽  
Efficiency Coefficient ◽  
Acid Biosynthesis ◽  
Continuous Cultures ◽  
Biomass Retention ◽  
Citric Acid Biosynthesis

AbstractThe effect of ammonium nitrate concentration in the citric acid biosynthesis by Aspergillus niger NC-12 in single-stage continuous cultures with biomass retention was investigated. Experiments were carried out in a BIOMER laboratory fermenter with 5 dm3 working volume. At the initial stage of each cultivation, the substrate in the bioreactor contained 1.5 g NH4NO3 dm−3. After 120 h onwards, the bioreactor was fed continuously at a constant dilution rate of 0.009 h−1. NH4NO3 concentration in the feed was varied from one culture to another, ranging between 0.5 g dm−3 and 2.5 g dm−3. Promising results were obtained when NH4NO3 concentration of 1.5 g dm−3 was used. The observed concentration of citric acid (c P) and yield of citric acid with respect to the introduced sucrose (Y P/S) were 117.88 g dm−3 and 78.59 %, respectively. The efficiency coefficient of citric acid biosynthesis (K ef) was very high, amounting to 83.38.

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