Optimization of Trace Metals Concentration on Citric Acid Production by Aspergillus niger NRRL 2001

Abstract

Citric acid is nowadays produced by submerged fermentation of Aspergillus niger. The process yield depends on the composition of the medium, as well as on the microorganism strain. In this work, the effect of Fe +3 , Zn +2 , and Mn +2 on citric acid production by A. niger NRRL 2001 is presented. The culture medium composition was glucose (120 g/L) KH 2 PO 4 (1.0 g/L); K 2 HPO 4 (1.0 g/L), MgSO 4 .7H 2 O (0.5 g/L), (NH 4 ) 2 SO 4 (3.0 g/L). The ions Fe +3 , Zn +2 , and Mn +2 had their concentrations changed according to an experimental design. The experiments were carried out in an orbital shaker at 200 rpm and 30°C. The strain produced an extracellular polysaccharide that was also quantified. The optimum experimental condition was found using 7.0 mg/L of Fe +3 and 6.5 mg/L of Zn +2 in absence of Mn +2 . No oxalic acid formation was observed using this experimental condition. Metal contents were not significant for the production of the polysaccharide. The highest production rate (2.95 g L −1 day −1 ) was reached after 10 days of fermentation. After this period, the productivity decreased slightly. In 20 days, the citric acid production rate (2.44 g L −1 day −1 ) was 82% of the highest productivity. The conversion into citric acid increased continuously, yielding 45.8% in 20 days of fermentation.

Enhanced itaconic acid production in Aspergillus niger using genetic modification and medium optimization

“…Since detailed analysis on trace metal concentration in A. niger media showed that citric acid production could be increased by combining low levels of Mn 2+ with high levels of Fe 2+ [ 11 ], and because Fe 2+ is a cofactor of hemoglobin to bind oxygen, we investigated this combination using medium 13. This medium contained a high concentration of Fe 2+ and no Mn 2+ .…”

Extraction of Cellulases Produced through Solid-State Fermentation by Trichoderma reesei CCT-2768 Using Green Coconut Fibers Pretreated by Steam Explosion Combined with Alkali

“…The fungus was grown in PDA medium at 30 • C for 5 days and then kept in the refrigerator (4 • C) for up to 3 months. To obtain a concentrated spore suspension, the spores were transferred from the plates to a medium of corncobs and peptone [36]. After 5 days at 30 • C, the medium was flooded with a sterile Tween 80 solution (0.5% v/v), mixed with a glass rod, and the suspension was collected.…”

Determination of citric and oxalic acid in fungi fermentation broth through HPLC-DAD and solid-phase extraction

“…A cartridge was conditioned and, the sample (1 mL) adjusted to pH 9, loaded through the cartridge ensuring a flow rate of 0.3 mL/min. The interferences were washed out using 1 mL of deionized water, while acid compounds were eluted five times with 0.5 mL of HCl (1 N), diluted with the mobile phase to a final volume of 5 mL, filtered through 0.2 µm syringe filter and later injected on HPLC [21,22].…”