THE CITRIC ACID FERMENTATION OF ASPERGILLUS NIGER

World Journal of Microbiology and …, 1999

A study was performed to understand the physiology and biochemical mechanism of citric acid accumulation during solid state fermentation of sweet potato using Aspergillus niger Yang No. 2. A low citrate-producing mutant was isolated followed by a comparative study of the fermentation process and selected physiological and biochemical parameters. In contrast with the parent strain, the mutant strain displayed lower concentrations, yields and production rates of citric acid, accompanied by higher concentrations, yields and production rates of oxalic acid. In addition, the mutant utilized starch at a lower rate although higher concentrations of free glucose accumulated in the cultures. Biochemical analyses revealed lower rates of glucose uptake and hexokinase activity of the mutant strain in comparison with the parent strain. It is proposed that, in common with submerged fermentation, over-production of citric acid in solid state fermentation is related to an increased glucose¯ux through glycolysis. At low glucose¯uxes, oxalic acid is accumulated.

Bayero Journal of Pure and Applied Sciences, 2014

The study involved the screening of fourteen isolates of Aspergillus niger for citric acid production from glucose. The study was aimed at screening and improving local strains of Aspergillus niger with potential for citric acid production. All the isolates screened produced varying amounts of citric acid, the highest was by the isolate designated CP3 which produced 12.81g/l and the least was B11 and O12 which produced 3.42g/l all after 6 days of submerged fermentation. The isolate CP3 was chosen for further studies. Strain improvement studies which was based on exposure of CP3 to ultraviolet irradiation for 10, 30 and 45 minutes increased citric acid yield to 22.20g/l (48.89% increase) by mutant M45 followed by a citric acid yield of 16.22g/l by the 30 minutes mutant (M30) and the least being M10 which produced 13.66g/l in all cases after 6 days of fermentation. The mutant (M45) also yielded higher amount of citric acid (19.64g/l) without methanol as additive compared to the parent strain (CP3) which gave a citric acid of 14.94g/l with the addition of methanol after six days (144h) of fermentation in both cases. Finding from this study showed that all the isolates have potential for citric acid production.

International Journal of Research and Innovation in Applied Science (IJRIAS, 2021

Citric acid is an Organic acids, commercially valuable product extensively used in different industries for various purposes. This study aimed at citric acid production by A.niger and A. awamori isolated from soil in Keffi using waste starch from corn milling factory. A.niger and A. awamori was isolated from soil in Keffi and identified using standard microbiology methods. Starch production media was prepared by following standard fermentation conditions. The citric acid produced was estimated using Gas Chromatography/Mass Spectrometry (GC/MS) method. The occurrence of Aspergillus species showed that Pyanku had the highest percentage occurrence with 100%. The screening for citric acid producing A.nigerand A. awamori showed that isolates from location A, C and D showed ability to produce citric acid. Effect of different temperature on citric acid production showed that A.awamoriA1produced highest at 28 o C with 3.10 mg/ml and A.awamoriA2 produced lowest at 26 O C (2.08mg/ml). A. niger F4 produced the highest at32 O C with 5.03mg/ml and A.niger F5 lowest at 26 O C with 3.10mg/ml. Fermentation duration showed duration by A. awamori A2 after 144hours with 5.00mg/ml and A. awamori A1 showed lowest yield after 24hours with 0.71mg/ml while A. niger F5 yield highest after 168 hours with 5.02mg/ml and A. niger F4 yield lowest after 24hours with 0.91mg/ml. Effect of pH on citric acid production showed that A. awamoriA1 yield highest at pH 4.5 with 5.19mg/ml while A. nigerF5 produced highest at pH 5.0 with citric acid yield of 5.69mg/l.

Bioresource Technology, 2004

The present investigation deals with citric acid production by some selected mutant strains of Aspergillus niger from cane molasses in 250 ml Erlenmeyer flasks. For this purpose, a conidial suspension of A. niger GCB-75, which produced 31.1 g/l citric acid from 15% (w/v) molasses sugar, was subjected to UV-induced mutagenesis. Among the 3 variants, GCM-45 was found to be a better producer of citric acid (50.0 ± 2a) and it was further improved by chemical mutagenesis using N-methyl, N-nitro-N-nitrosoguanidine (MNNG). Out of 3,2-deoxy-D D -glucose resistant variants, GCMC-7 was selected as the best mutant, which produced 96.1 ± 1.5 g/l citric acid 168 h after fermentation of potassium ferrocyanide and H 2 SO 4 pre-treated blackstrap molasses in Vogel's medium. On the basis of kinetic parameters such as volumetric substrate uptake rate (Q s ), and specific substrate uptake rate (q s ), the volumetric productivity, theoretical yield and specific product formation rate, it was observed that the mutants were faster growing organisms and produced more citric acid. The mutant GCMC-7 has greater commercial potential than the parental strain with regard to citrate synthase activity. The addition of 2.0 · 10 À5 M MgSO 4 AE 5H 2 O into the fermentation medium reduced the Fe 2þ ion concentration by counter-acting its deleterious effect on mycelial growth. The magnesium ions also induced a loose-pelleted form of growth (0.6 mm, diameter), reduced the biomass concentration (12.5 g/l) and increased the volumetric productivity of citric acid monohydrate (113.6 ± 5 g/l).

Two starchy substrates like pumpkin and cane molasses were selected for citric acid fermentation by using gamma ray induced mutant strains of 14/20 and 79/20 of A. niger under surface culture condition. Citric acid production was also different with various fermentation media by A. niger 14/20 and 79/20 strains. It was found to increase with the increase of fermentation period and maximum citric acid was found on day 13. In the presence of Prescott salt citric acid production was found lower than the absence of Prescott salt. Without Prescott salt highest values of citric acid production was found in mixed fermentation medium which were about 14.86 mg/ml and 14.44 mg/ml for A. niger 14/20 and 79/20 strains respectively, lowest production of citric acid was found in molasses medium for A. niger 14/20 and 79/20 strains were 7.72 and 7.57 mg/ml respectively. Whereas in the presence of Prescott salt, lowest production of citric acid in Pumpkin medium was found 2.86 mg/ml for A. niger 14/20 and 2.7 mg/ml for A. niger 79/20. Highest amount of citric acid was produced in molasses medium 4.88 mg/ml for A. niger 14/20 on day 13 with the presence of Prescott salt whereas 4.75 mg/ml for A. niger 79/20 strains respectively. Mixed substrate prepared with molasses and pumpkin media was proved to be the best and potential for citric acid production.

Biotechnology Letters, 1995

Aspergillus niger SZ was grown under citric acid accumulation conditions in a 11 bioreactor. Radioactive citric acid was added during the fermentation to the culture medium. The accumulation of radioactive citric acid in the mycellium was measure by measuring radioactive CO2 in the offgas. Evidence was obtained of significant turnover and metabolism of exogenous citric acid even during the phase of maximum accumulation into the medium.

Folia Microbiologica, 1992

Two starchy substrates like pumpkin and cane molasses were selected for citric acid fermentation by using gamma ray induced mutant strains of 14/20 and 79/20 of A. niger under surface culture condition. Citric acid production was also different with various fermentation media by A. niger 14/20 and 79/20 strains. It was found to increase with the increase of fermentation period and maximum citric acid was found on day 13. In the presence of Prescott salt citric acid production was found lower than the absence of Prescott salt. Without Prescott salt highest values of citric acid production was found in mixed fermentation medium which were about 14.86 mg/ml and 14.44 mg/ml for A. niger 14/20 and 79/20 strains respectively, lowest production of citric acid was found in molasses medium for A. niger 14/20 and 79/20 strains were 7.72 and 7.57 mg/ml respectively. Whereas in the presence of Prescott salt, lowest production of citric acid in Pumpkin medium was found 2.86 mg/ml for A. niger 14/20 and 2.7 mg/ml for A. niger 79/20. Highest amount of citric acid was produced in molasses medium 4.88 mg/ml for A. niger 14/20 on day 13 with the presence of Prescott salt whereas 4.75 mg/ml for A. niger 79/20 strains respectively. Mixed substrate prepared with molasses and pumpkin media was proved to be the best and potential for citric acid production.

American Journal of Food and Nutrition, 2013

Under surface culture condition, a number of cheap indigenous raw materials like cane molasses and jackfruits were selected for citric acid fermentation and gamma ray induced mutant strains of 14/20 and 79/20 of Aspergillus niger were used. The rate of citric acid production was also influenced by biomass production and residual sugar used. In both cases on the day 13 without presence of Prescott salt for the mutant strain of Aspergillus niger 14/20 the citric acid production was highest. The biomass production was found different in various fermentation medium. It was found to increase with the increase of fermentation period and maximum biomass was found on day 13. It is also found that biomass production was higher in mutant strain of A. niger 14/20 than 79/20. In addition to this, wet-weight biomass was higher than dry weight biomass. Without presence of Prescott salt, wet weight of mycelial body of the fungus Aspergillus niger 14/20 was found highest on day 13 in mixed substrat...

Bioprocess Engineering, 1996

In this work, the citric acid production in solid state culture was performed, evaluating the isolated effect and interactions of particle size and liquid phase employed, by means of the factorial design of first order. The results indicate that the particle size is the most determinant variable. An analysis comparing submerged and solid state in optimal conditions was performed. When solid state culture was used,

Aspergillus niger Yang No. 2 and its mutant strain SL1 were grown in solid state fermentation. Samples were taken after 2, 4 and 6 days of incubation and the mycelia were analysed for their intracellular concentrations of some organic acids and adenylates and the activities of selected enzymes. Strain Yang No. 2 contained high concentrations of citrate with very little oxalate, while strain SL1 contained lower concentrations of citrate but considerably higher concentrations of oxalate. As the fermentation proceeded, strain Yang No. 2 showed a much higher ratio of ATP:AMP than did strain SL1. In addition, the enzyme ATP:citrate lyase became undetectable during citrate accumulation in strain Yang No. 2, while its activity remained high during oxalate accumulation in strain SL1. It is proposed that citrate accumulation by strain Yang No. 2 during solid state fermentation is due to blockage of its metabolism in the mitochondrion via inhibition of isocitrate dehydrogenase by the high ATP:AMP ratio, and in the cytosol by repression of ATP:citrate lyase activity.