Citric Acid Production Research Articles

Transcriptomics identify the triggering of citrate export as the key event caused by manganese deficiency in Aspergillus niger.

Citric acid is produced on industrial scale by batch fermentation of the filamentous fungus Aspergillus niger. High-yield citric acid production requires a low (<5 ppb) manganese(II) ion concentration in the culture broth. However, the requirement for this deficiency has not been investigated on a functional genomics level. Here, we compared the transcriptome of a citric acid hyper-producer A. niger strain grown under citric acid-producing conditions in 6-L scale bioreactors at Mn2+ ion-deficient (5 ppb) and Mn2+ ion-sufficient (100 ppb) conditions at three early time points of cultivation. We observed that Mn2+ deficiency triggers an upregulation of the citrate exporter gene cexA and provides functional evidence that this event is responsible for citrate overflow. In addition to the industrial relevance, this is the first study that examined the role of Mn2+ ion deficiency in a heterotrophic eukaryotic cell on a genome-wide scale.

Effects of phosphorus-solubilizing bacteria and biochar application on phosphorus availability and tomato growth under phosphorus stress

BackgroundPhosphorus-solubilizing bacteria (PSB) are vital in converting insoluble phosphorus into a soluble form that plants can readily absorb and utilize in soil. While previous studies have mainly focused on the extracellular secretion of microorganisms, few have explored the intricate intracellular metabolic processes involved in PSB-mediated phosphorus solubilization.ResultsHere, we uncovered that Ca3(PO4)2 could serve as a source of insoluble phosphorus for the PSB, Pseudomonas sp. NK2. High-performance liquid chromatography (HPLC) results indicated higher levels of organic acids released from insoluble phosphorus compared to a soluble phosphorus source (KH2PO4), with acetic acid released exclusively under insoluble phosphorus condition. Moreover, non-target metabolomics was employed to delve into the intracellular metabolic profile. It unveiled that insoluble phosphorus significantly enhanced the tricarboxylic acid cycle, glycolysis, glyoxylic acid metabolism, and other pathways, leading to the production of acetic acid, gluconic acid, oxalic acid, and citric acid for insoluble phosphorus solubilization. In our quest to identify suitable biochar carriers, we assessed seven types of biochar through the conjoint analysis of NBRIP medium culture and application to soil for 30 days, with cotton straw-immobilized NK2 emerging as the most potent phosphorus content provider. Lastly, NK2 after cotton straw immobilization demonstrated the ability to enhance biomass, plant height, and root development of Solanum lycopersicum L. cv. Micro Tom.ConclusionsPseudomonas sp. NK2 with cotton straw biochar could enhance phosphorus availability and tomato growth. These findings bear significant implications for the practical application of phosphorus-solubilizing bacteria in agricultural production and the promotion of environmentally sustainable farming practices.

Stimulation of citric acid production by heat shock promoting &lt;i&gt;Aspergillus niger&lt;/i&gt; using nitrogen enriched &lt;i&gt;Dioscorea bulbifera&lt;/i&gt;

High cost of substrate and how to stimulate citric acid are among the factors that mitigate citric acid production. Exploiting a cheap substrate for citric acid production will be a viable alternative in order to reduce the cost of citric acid production. Therefore, the aim of this research was to evaluate the potential of wild Dioscorea bulbifera tubers for citric acid production. Experimental procedures were designed to determine the effect of different concentrations of wild Dioscorea bulbifera, different nitrogen sources and effect of different concentrations of nitrogen sources on citric acid production. The data obtained were analyzed using one- way analysis of variance (ANOVA). The results of the experiment showed that wild Dioscorea bulbifera tuber was able to produce citric acid. The concentration of acid produced increased from 5 % to 20 % citric acid up to 8.5 ±1.0 g/lafter 96 hours of fermentation. Among the different nitrogen sources used to supplement wild Dioscorea bulbifera, the medium with ammonium nitrate produced the highest citric acid concentration of 10.5 ±1.5 g/l after 96 hours of fermentation. Meanwhile, when the concentration of the amonium nitrate were varied, 0.4 % was the optimum for the maximum citric acid concentration of 14.8 ±2.0 g/l after 96 hours of fermentation (P&lt; 0.05). In conclusion, Dioscorea bulbifera tubers is suitable for citric acid production and supplementation of the medium with ammonium nitrate as a nitrogen source had a positive effect on the yield.

Harnessing of low cost agro-industrial waste substrates for the optimum production of citric acid: A review

Harnessing of low cost agro-industrial waste substrates for the optimum production of citric acid: A review

Citric acid production by Brazilian garlic Aspergillus welwitschiae strains using orange residues

The global production of citrus fruits has expressively grown resulting in large amounts of residue. Orange residues are rich in carbon and could be used as substrates for production of biomolecules such as citric acid. In this study, wild and mutant Aspergillus welwitschiae strains isolated from Brazilian garlic were used to produce citric acid from orange residues, using solid-state fermentation. The results showed that the mutant A. welwitschiae UELAs 15.262/35 produced great amount of citric acid in the fourth day of solid-state fermentation using total and reducing sugars and producing cellulases. On the other hand, there was no production of citric acid by wild A. welwitschiae UELAs 15.262. The use of total and reducing sugars and the production of cellulases by A. welwitschiae UELAs 15.262 were detected, suggesting the use of carbon sources for the production of other metabolites. The great use of reducing sugars and cellulases production by A. welwitschiae UELAs 15.262/35 indicated the consume of carbon sources from the orange residue to produce citric acid at early times of fermentation. These findings lead to the possibility of biotechnological valorization of orange residues for acid organic production by A. welwitschiae strain.

Production of Citric Acid from Different Aspergillus species Obtained from Soil

The genus Aspergillus is considered highly important in the production of various types of enzymes and organic acids. Aspergillus species produce organic acids such as citric acid, itaconic acid, and malic acid, which are one of the most important alternate techniques for chemical processes. Citric acid is an essential primary agricultural product that is extensively used in the world. It acts as an intermediate in the tricarboxylic acid cycle (citric acid cycle) during the oxidation of carbohydrates to carbon dioxide. Citric acid has an important role in industries involving the production of food products, beverages, pharmaceutical and agricultural products, detergents, and cosmetics. The production of citric acid, a crucial agricultural commodity with widespread applications in various industries including food, beverages, pharmaceuticals, agriculture, detergents, and cosmetics, heavily relies on microbial fermentation. The great demand for citric acid due to its wide industrial applications and less toxicity. Citric acid can be produced using less expensive substrates that are renewable too. In this work, Aspergillus species was isolated from the soil source, collected in different localities of Chhatrapati Sambhajinagar. The total 90 different isolates are isolated among these the 20 different Aspergillus species are isolated and pure culture by using potato dextrose agar (PDA) Czapek dox agar medium and study the effect of different media on growth and sporulation of different Aspergillus species and the quantitative analysis of citric acid production was done by titration method with help of NaOH and phenolphthalein indicator. The main reason for the study increases is the large number of applications that can be found for citric acid, primarily in the food and pharmaceutical industries

Utilization of banana peel waste for the production of bioethanol and other high-value-added compounds

Bananas (Musa sp.) are one of the most produced crops worldwide, surpassing 100 million tons per year, and considering that approximately 30 % of their weight consists of peels, the annual generation of these residues is significant. Banana residues are rich in nutrients; nowadays, they are all disposed of in landfills. As a novelty, this work showed that it could be used for other things, such as alcohol, D-Limonene, and citric acid production. This study characterized the biomass, optimized pretreatment, and enzymatic hydrolysis and evaluated the fermentation process using this biomass, using the central composite design (CCD) methodology. The planning variables included sulfuric acid (H2SO4) concentration, banana peel waste mass in the pretreatment stage, and commercial cellulase enzyme (Sigma-Aldrich) concentration in the enzymatic hydrolysis stage. The responses quantified were sugars, ethanol, and acids using high-performance liquid chromatography, and the D-Limonene content was determined on a gas chromatograph coupled to a mass spectrometer. The highest yield of total reducing sugars found after enzymatic hydrolysis was 11.88 g/L, while the ethanol yield was 1.37 g/L. In the recovery of D-Limonene, the obtained value was 0.56 mg/g. The values of fermentable sugars confirm banana peel waste as a potential biomass for biorefinery processes. Furthermore, the possibility of an integrated D-Limonene recovery is essential in obtaining bioproducts. In this sense, it can be concluded that utilizing these residues is promising in reducing environmental issues and valorizing food waste.

Generation of citric acid-hyperproducers independent of methanol effect by high-level expression of cexA encoding citrate exporter in Aspergillus tubingensis.

Methanol reportedly stimulates citric acid (CA) production by Aspergillus niger and A. tubingensis; however, the underlying mechanisms remain unclear. Here, we elucidated the molecular functions of the citrate exporter gene cexA in relation to CA production by Aspergillus tubingensis WU-2223L. Methanol addition to the medium containing glucose as a carbon source markedly increased CA production by strain WU-2223L by 3.38-fold, resulting in a maximum yield of 65.5 g/L, with enhanced cexA expression. Conversely, the cexA-complementing strain with the constitutive expression promoter Ptef1 (strain LhC-1) produced 68.3 or 66.7 g/L of CA when cultivated without or with methanol, respectively. Additionally, strain LhC-2 harboring two copies of the cexA expression cassette produced 80.7 g/L of CA without methanol addition. Overall, we showed that cexA is a target gene for methanol in CA hyperproduction by A. tubingensis WU-2223L. Based on these findings, methanol-independent CA-hyperproducing strains, LhC-1 and LhC-2, were successfully generated.

Assessing Waste Sunflower Oil as a Substrate for Citric Acid Production: The Inhibitory Effect of Triton X-100

In this study, waste sunflower oils were evaluated as substrates for citric acid (CA) production by Yarrowia lipolytica IFP29 (ATCC 20460). This strain was selected based on its capacity to produce organic acids in a selective medium. Attempts were made to optimize the process using the Taguchi statistical method in terms of the oil polarity, oil concentration, fermentation time, and Triton X-100 concentration. The results indicated that Y. lipolytica IFP29 utilized waste sunflower oil as a substrate and produced a maximum CA of 32.17 ± 1.44 g/L. Additionally, Triton X-100 inhibited the production of CA. For this reason, this process could not be optimized. These results were obtained by periodically adjusting the pH with NaOH during the fermentation period. On the other hand, a new experimental design was created without Triton X-100. As a buffering agent, 2-morpholinoethanesulfonic acid monohydrate (MES) was used to prevent a drop in pH; the maximum concentration of CA was found to be 20.31 ± 2.76. The optimum conditions were as follows: 90 g/L of waste sunflower oil with a polarity of 16 and 12 days of fermentation. According to the analysis of variance results, the effects of factors other than polarity on CA production were found to be significant (p &lt; 0.05).

ISOLATION AND SCREENING OF MICROORGANISMS FOR CITRIC ACID PRODUCTION

Citric acid is a weak acid and naturally occurring antioxidant. Due to its wide application in the food industry, cosmetics and manufacturing cleaning products, Citric acid is artificially synthesized by exploiting microorganisms, especially fungi. With an aim of isolating and screening the potential microorganisms for citric acid production, the present study was carried out by collecting samples of decaying fruits and vegetables from the local market of Kalaburagi, Karnataka, India viz., Citrus limon, Citrus sinensis, Vitis vinifera, Malus pumila, Ananas comosus, Solanum tuberosum, Punica granatum, Citrullus lanatus, Musa paradisiaca, Solanum lycopersicum, Phaseolus vulgaris, Mangifera indica, Manilkara zapota, Beta vulgaris, Saccharum officinarum, Ipomoea batatas, Daucus carota, Psidium guajava, Solanum melongena and Abelmoschus esculentus. A total of 20 isolates have been isolated from the samples, out of 20 fungal isolates, 7 isolates viz., KLV03, KLV04, KLV07, KLV10, KLV11, KLV13 and KLV14 showed significant acid unitage values of 3.00, 1.88, 3.36, 1.31, 2.35, 1 and 1 respectively. Among these, KLV07 isolate showed the highest acid unitage value of 3.36.

Unlocking nature's sweet secret for citric acid production from wood sugars: Evaluation of microbial strains and environmental impacts

This study investigates a novel approach by utilizing wood-derived sugars as a substrate for microbial citric acid (CA) production. Additionally, it examines the environmental implications through an ex-ante life cycle assessment (LCA). Various microbial strains including six yeast strains from the Yarrowia genus, three filamentous fungi strains from the Aspergillus genus, and eight bacterial strains were evaluated for their potential in CA production. The investigation primarily focused on optimizing citric acid production by considering various factors such as substrate concentrations, nitrogen levels, alcohols, surfactants, and the potential of non-commercial strains. The study yielded promising results, with the highest CA yields recorded as follows: 5.7 g/L from bacterial fermentation, 36.8 g/L from yeast fermentation, and 67.7 g/L from fungi fermentation. Furthermore, by applying an ex-ante LCA, the study assessed the environmental impact of citric acid production. Results indicated a significant reduction in environmental footprint when scaled up, with emissions decreasing from 235 to 585.8 kgCO2eq/kg at the laboratory scale to 4–6 kgCO2eq/kg at the larger scale.

Enhanced Citric Acid Production through Aspergillus niger: Insights from Fermentation Studies Using Sugarcane Molasses.

The production of citric acid, a vital agricultural commodity utilized across various industries such as food, beverages, pharmaceuticals, agriculture, detergents, and cosmetics, predominantly relies on microbial fermentation, with Aspergillus niger accounting for approximately 90% of global production. In this study, we aimed to optimize the key factors influencing citric acid production, with a focus on strains, fermentation techniques, and carbon sources, particularly sugarcane molasses. A. niger, sourced from the Botany department/Biotechnology laboratories at Govt. College of Science, Lahore, was employed for citric acid production. The process involved inoculum preparation through spore collection from 3 to 5 days of cultured PDA slants. The fermentation medium, comprising cane molasses with a 15% sugar concentration, was meticulously prepared and optimized for various factors, including magnesium sulfate, potassium ferrocyanide, time of addition of potassium ferrocyanide, ammonium oxalate, and calcium chloride. Our optimization results shed light on the significant impact of different factors on citric acid production. For instance, the addition of 0.4 g/L magnesium sulfate led to a maximum yield of 75%, while 2 g/L potassium ferrocyanide, added at 24 h, achieved a yield of 78%. Remarkably, ammonium oxalate, at a concentration of 10 g/L, resulted in a notable 77% yield. Conversely, the addition of calcium chloride exhibited negligible effects on citric acid production, with the control group yielding more at 78%. Our study underscores the potential for optimizing factors to enhance citric acid production by A. niger in submerged fermentation. These findings highlight the pivotal role of magnesium sulfate, potassium ferrocyanide, and ammonium oxalate in augmenting citric acid yields while emphasizing the minimal impact of calcium chloride. Ultimately, these insights contribute to advancing our understanding of microbial citric acid biosynthesis, providing valuable implications for industrial applications and future research endeavors.

Mitochondrial dysfunction results in enhanced adrenal androgen production in H295R cells

The role of mitochondria in steroidogenesis is well established. However, the specific effects of mitochondrial dysfunction on androgen synthesis are not fully understood. In this study, we investigate the effects of various mitochondrial and metabolic inhibitors in H295R adrenal cells and perform a comprehensive analysis of steroid and metabolite profiling. We report that mitochondrial complex I inhibition by rotenone shifts cells toward anaerobic metabolism with a concomitant hyperandrogenic phenotype characterized by rapid stimulation of dehydroepiandrosterone (DHEA, 2 h) and slower accumulation of androstenedione and testosterone (24 h). Screening of metabolic inhibitors confirmed DHEA stimulation, which included mitochondrial complex III and mitochondrial pyruvate carrier inhibition. Metabolomic studies revealed truncated tricarboxylic acid cycle with an inverse correlation between citric acid and DHEA production as a common metabolic marker of hyperandrogenic inhibitors. The current study sheds light on a direct interplay between energy metabolism and androgen biosynthesis that could be further explored to identify novel molecular targets for efficient treatment of androgen excess disorders.

Reconstruction of a genome-scale metabolic model and in-silico flux analysis of Aspergillus tubingensis: a non-mycotoxinogenic citric acid-producing fungus

BackgroundAspergillus tubingensis is a citric acid-producing fungus that can utilize sugars in hydrolysate of lignocellulosic biomass such as sugarcane bagasse and, unlike A. niger, does not produce mycotoxins. To date, no attempt has been made to model its metabolism at genome scale.ResultsHere, we utilized the whole-genome sequence (34.96 Mb length) and the measured biomass composition to reconstruct a genome-scale metabolic model (GSMM) of A. tubingensis DJU120 strain. The model, named iMK1652, consists of 1652 genes, 1657 metabolites and 2039 reactions distributed over four cellular compartments. The model has been extensively curated manually. This included removal of dead-end metabolites and generic reactions, addition of secondary metabolite pathways and several transporters. Several mycotoxin synthesis pathways were either absent or incomplete in the genome, providing a genomic basis for the non-toxinogenic nature of this species. The model was further refined based on the experimental phenotypic microarray (Biolog) data. The model closely captured DJU120 fermentative data on glucose, xylose, and phosphate consumption, as well as citric acid and biomass production, showing its applicability to capture citric acid fermentation of lignocellulosic biomass hydrolysate.ConclusionsThe model offers a framework to conduct metabolic systems biology investigations and can act as a scaffold for integrative modelling of A. tubingensis.

Isolation of Aspergillus sp from some Decomposing Fruits and Vegetables from Banana Rhyzosphere Soil for Citric Acid Production

Aims: The general objective of this study is to isolate certain strains capable of producing citric acid. Place and Duration of Study: Sample collection was carried out on two types of organic matter. Sampling was done from February to April 2021 in 3 municipalities in Abidjan with 10 samples per site. Methodology: To carry out this work, isolation and purification of Aspergillus sp strains were carried out. Macroscopic and microscopic identifications of the mold isolates were carried out. The search for aflatoxin-producing molds was carried out. The analysis ended with a screening of molds capable of synthesizing citric acid. Results: Aspergillus niger, Aspergillus sp1 and Aspergillus sp2 showed no fluorescence, while Aspergillus flavus, Aspergillus candidus and Aspergillus fumigatus showed fluorescent spots, indicating the presence of aflatoxin. Conclusion: Aspergillus isolates capable of producing citric acid were isolated during this study. Aspergillus niger, Aspergillus sp1 and Aspergillus sp2 do not produce aflatoxin and have the capacity to synthesize citric acid.

Isolation, screening, and characterization of the newly isolated osmotolerant yeast Wickerhamomyces anomalus BKK11-4 for the coproduction of glycerol and arabitol.

This study explored the isolation and screening of an osmotolerant yeast, Wickerhamomyces anomalus BKK11-4, which is proficient in utilizing renewable feedstocks for sugar alcohol production. In batch fermentation with high initial glucose concentrations, W. anomalus BKK11-4 exhibited notable production of glycerol and arabitol. The results of the medium optimization experiments revealed that trace elements, such as H3BO3, CuSO4, FeCl3, MnSO4, KI, H4MoNa2O4, and ZnSO4, did not increase glucose consumption or sugar alcohol production but substantially increased cell biomass. Osmotic stress, which was manipulated by varying initial glucose concentrations, influenced metabolic outcomes. Elevated glucose levels promoted glycerol and arabitol production while decreasing citric acid production. Agitation rates significantly impacted the kinetics, enhancing glucose utilization and metabolite production rates, particularly for glycerol, arabitol, and citric acid. The operational pH dictated the distribution of the end metabolites, with glycerol production slightly reduced at pH 6, while arabitol production remained unaffected. Citric acid production was observed at pH 6 and 7, and acetic acid production was observed at pH 7. Metabolomic analysis using GC/MS identified 29 metabolites, emphasizing the abundance of sugar/sugar alcohols. Heatmaps were generated to depict the variations in metabolite levels under different osmotic stress conditions, highlighting the intricate metabolic dynamics occurring post-glucose uptake, affecting pathways such as the pentose phosphate pathway and glycerolipid metabolism. These insights contribute to the optimization of W. anomalus BKK11-4 as a whole-cell factory for desirable products, demonstrating its potential applicability in sustainable sugar alcohol production from renewable feedstocks.

Potencial Citric Acid Production by Fungi Using Hemicellulosic Hydrolysate of Coffee Husk as Substrate

Objective: The aim of this experimental assay was to produce citric acid via submerged fermentation, using hemicellulose hydrolysate from coffee husks as main substrate. Theoretical framework: Obtaining citric acid through fermentation processes, especially submerged fermentation, has become viable due to the use of low-cost materials, such as industrial subproducts derived from green biomass. Methodology: The hemicellulose hydrolysate was obtained from the acid hydrolysis process of the coffee husk. The strains of the fungi Aspergillus niger, Aspergillus westerdijkiae and Rhizopus sp. were employed to carry out the fermentation assays. A bioreactor consisting of a 500 ml flat-bottomed flask was used, with an inlet for supplying air and an outlet for removing samples Results and Conclusion: The obtained results showed an increase in number of spores of the studied fungi as well as citric acid accumulation during the first 72 h of fermentation. On the other hand, after 96 h of fermentation citric acid concentration began to decrease indicating its consumption by the studied fungi, probably due to the lack of nitrogen sources and the cellular stress caused by the mixed composition of the hemicellulose hydrolysate. Implications of the research: There is a need to study the interaction between the nitrogenous nutrients to be added to the fermentation medium and the concentration of reducing sugars as the sole carbon source in the lignocellulosic hydrolysate. Originality/value: This work highlights the potential production of citric acid by fungi using a coffee husk as a renewable biomass.

The superiority of citrate as denitrification carbon source in an activated sludge system: Substrate metabolism, electron transfer and microbial characteristics

Citrate, a low-molecular-weight organic substance, was rich in citric acid production wastewater with the potential for reuse. Although citrate has been extensively used as a denitrification carbon source, previous studies mainly focus on its application by pure cultures of denitrifying bacteria. The information about denitrification performance and mechanisms using citrates as carbon source in an activated sludge system is still very limited. This study investigated the denitrification efficiency and mechanisms using citrate as carbon source through a long-term operation of continuous reactor. Under the C/N ratio of 5, the total nitrogen (TN) removal efficiency using citrate as carbon source was 93.21 ± 4.24 %, which was comparable to that of acetate (99.84 ± 0.44 %), and much higher than glucose (65.64 ± 3.86 %). Higher denitrification rate was achieved using citrate as carbon source, which was slightly higher than acetate and >4 times of that using glucose. Due to the high activities of denitrifying enzymes including nitrite reductase (NIR), nitric oxide reductase (NOR) and nitrous oxide reductase (N2OR), there was almost no NO2‐-N and N2O accumulation in the reactor fed with citrate, which was superior to the reactors fed with acetate or glucose. Azoarcus (48.2 %) with the ability of complete denitrification was the most dominant bacteria in the reactor fed with citrate. Considering denitrification kinetics, activities of key enzymes and microbial community characteristics, citrate had a superiority as an effective denitrification carbon source.

Nutritional Composition and Therapeutic Potential of Pineapple Peel - A Comprehensive Review.

Pineapple (Ananas comosus), the succulent and vibrant tropical fruit, is a symbol of exoticism and sweetness that captures the hearts and palates of people around the world. The pineapple peel, often considered as waste, has garnered attention for its potential applications. The pineapple peel is rich in essential nutrients, including calcium, potassium, vitamin C, carbohydrates, dietary fiber, and water, making it beneficial for the digestive system, weight management, and overall balanced nutrition. It contains significant amounts of sugars such as sucrose, glucose, and fructose, along with citric acid as the predominant organic acid. The peel also contains bromelain, a proteolytic enzyme known for its digestive properties. Studies have highlighted the pharmacological properties of pineapple peel, such as its potential anti-parasitic effects, alleviation of constipation, and benefits for individuals with irritable bowel syndrome (IBS). Efforts are being made to promote the utilization of pineapple peel as a valuable resource rather than mere waste. Its applications range from the production of vinegar, alcohol, and citric acid to the development of various food products, including squash, syrup, jelly, and pickles. Further research and innovation are required to fully explore the potential of pineapple peel and establish sustainable practices for its utilization, contributing to waste reduction and the development of value-added products.

Improving dietary citric acid production by the wild-type Aspergillus niger ASP26 strain isolated from date by-product.

This research investigates citric acid (CA) synthesis using the indigenous strain Aspergillus niger ASP26, which was isolated from date by-products. The study initially involved isolating fungi capable of CA production and identifying the most potent strain based on its characteristic enzymatic activity. A. niger ASP26 was acknowledged in a previous study for its remarkable ability to produce extracellular enzymes, such as cellulase and amylase, which enable it to degrade organic materials effectively. After the identification phase, these isolates were screened for CA production using a modified Czapek-Dox medium. The research identified significant factors affecting CA production in submerged fermentation, including pH, carbon source, inoculum size, and fermentation time. Optimal conditions were determined for A. niger ASP26, resulting in a maximum CA yield of 16.89 g/L. These conditions included a 2.5% spore suspension at 2 × 107 spores/mL, an initial glucose concentration of 125 g/L, and incubation at 30°C for 144 h. Notably, A. niger ASP26 demonstrated the ability to produce CA under stress conditions as well. Citric acid is essential for various biological processes, such as cellular respiration, and is naturally present in citrus fruits. It also serves as a preservative and flavor enhancer in processed foods and beverages. The ability of A. niger ASP26 to produce CA from agricultural residues positions it as a viable candidate for sustainable CA production, harnessing the value from organic waste materials.