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What is the purpose of filtering broth obtained from fermentation?
What is the purpose of filtering broth obtained from fermentation?
How is citric acid typically precipitated from the filtrate?
How is citric acid typically precipitated from the filtrate?
What methods may be optional for the extraction of citric acid?
What methods may be optional for the extraction of citric acid?
What technique is primarily used to obtain citric acid crystals?
What technique is primarily used to obtain citric acid crystals?
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Which form is NOT a way in which citric acid is marketed?
Which form is NOT a way in which citric acid is marketed?
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What is a major disadvantage of using yeasts in citric acid production?
What is a major disadvantage of using yeasts in citric acid production?
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Which phase is NOT part of the citric acid production process by yeasts on a laboratory scale?
Which phase is NOT part of the citric acid production process by yeasts on a laboratory scale?
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In industrial citric acid production, which phase comes after the exponential growth phase?
In industrial citric acid production, which phase comes after the exponential growth phase?
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What can affect the amount of isocitric acid produced during fermentation?
What can affect the amount of isocitric acid produced during fermentation?
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What temperature range is typically used for bacterial fermentation?
What temperature range is typically used for bacterial fermentation?
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How do citric acid concentrations from bacterial production compare to those from fungi or yeasts?
How do citric acid concentrations from bacterial production compare to those from fungi or yeasts?
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Which of the following is a potential advantage of using n-alkanes over carbohydrates in citric acid production?
Which of the following is a potential advantage of using n-alkanes over carbohydrates in citric acid production?
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What is a common control measure during the fermentation phase for citric acid production?
What is a common control measure during the fermentation phase for citric acid production?
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What is one primary application of citric acid in the chemical industry?
What is one primary application of citric acid in the chemical industry?
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Which of the following is NOT a characteristic feature of citric acid production stability issues?
Which of the following is NOT a characteristic feature of citric acid production stability issues?
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Citric acid can serve as a replacement for which of the following substances in the detergent industry?
Citric acid can serve as a replacement for which of the following substances in the detergent industry?
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In the process of citric acid production, what temperature range is recommended for low spore storage?
In the process of citric acid production, what temperature range is recommended for low spore storage?
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Which fungus has been observed to accumulate citric acid during fermentation?
Which fungus has been observed to accumulate citric acid during fermentation?
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What is one of the roles citric acid plays in the food and beverage industry?
What is one of the roles citric acid plays in the food and beverage industry?
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Which application of citric acid involves its use in the environmental sector?
Which application of citric acid involves its use in the environmental sector?
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What is a challenge associated with maintaining citric acid production stability?
What is a challenge associated with maintaining citric acid production stability?
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What is the primary microorganism used in surface fermentation for citric acid production?
What is the primary microorganism used in surface fermentation for citric acid production?
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What is the temperature range for incubating A.niger during citric acid production?
What is the temperature range for incubating A.niger during citric acid production?
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Which method is used to separate the biomass from the broth after fermentation?
Which method is used to separate the biomass from the broth after fermentation?
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How is citric acid precipitated from the solution?
How is citric acid precipitated from the solution?
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What is a notable advantage of continuous culture over batch culture?
What is a notable advantage of continuous culture over batch culture?
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What is used to sterilize the air supply in the fermentation process?
What is used to sterilize the air supply in the fermentation process?
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What type of fermentation employs a mycelium layer formed by A.niger?
What type of fermentation employs a mycelium layer formed by A.niger?
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What mechanical devices assist in increasing productivity in fermentation by returning cells to the fermentor?
What mechanical devices assist in increasing productivity in fermentation by returning cells to the fermentor?
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What is one of the primary advantages of using immobilized microbial cells over free cells?
What is one of the primary advantages of using immobilized microbial cells over free cells?
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Which of the following is a disadvantage of using mutant strains of A.niger?
Which of the following is a disadvantage of using mutant strains of A.niger?
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Which substrates can be used in the fermentation process involving A.niger?
Which substrates can be used in the fermentation process involving A.niger?
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What challenge is presented by immobilized cell systems?
What challenge is presented by immobilized cell systems?
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What is one of the main techniques used to produce mutant strains of A.niger?
What is one of the main techniques used to produce mutant strains of A.niger?
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Which bacteria are noted as the most promising for citric acid production?
Which bacteria are noted as the most promising for citric acid production?
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Identify a benefit of mutant strains of A.niger related to citric acid production.
Identify a benefit of mutant strains of A.niger related to citric acid production.
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What is the primary carbon source used for producing citric acid with A.niger?
What is the primary carbon source used for producing citric acid with A.niger?
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Which method can enhance the purity of citric acid after fermentation?
Which method can enhance the purity of citric acid after fermentation?
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What aspect of the fermentation process does surface or submerged techniques relate to?
What aspect of the fermentation process does surface or submerged techniques relate to?
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Which pathway is involved in citric acid biosynthesis?
Which pathway is involved in citric acid biosynthesis?
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What percentage of glucose is typically available for the production of mycelia and CO2 during fermentation?
What percentage of glucose is typically available for the production of mycelia and CO2 during fermentation?
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How does the strain of A.niger affect citric acid production?
How does the strain of A.niger affect citric acid production?
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Which components are essential for A.niger growth in media?
Which components are essential for A.niger growth in media?
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In what type of media are citric acid yields found to be higher for A.niger?
In what type of media are citric acid yields found to be higher for A.niger?
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Which of the following is a key enzyme for citric acid biosynthesis from sucrose by A.niger?
Which of the following is a key enzyme for citric acid biosynthesis from sucrose by A.niger?
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Study Notes
Biotechnology of Citric Acid Production
- Citric acid is a tricarboxylic acid (2-hydroxy-1,2,3-propanetricarboxylic acid) naturally found in various fruits, vegetables, and in animal tissues.
- Early attempts at citric acid production from sucrose using Mucor and Penicillium strains in 1893 were unsuccessful due to difficulties in selecting appropriate microorganisms, and issues like microbial degeneration, contamination, and excessive fermentation times.
- A. niger is widely used for citric acid production. In 1917, Currie described the successful production of citric acid using Aspergillus niger.
- The process involves growing A. niger in a low pH medium supplemented with 15% sucrose and nutrients, converting a significant portion (55%) of the sugar into citric acid.
- The anhydrous form of citric acid is produced at temperatures exceeding 36.6°C, while the monohydrate form is produced at temperatures up to 36.0°C.
- The global annual production of citric acid is considerable and spans across many countries.
Microorganisms Used for Citric Acid Production
- Aspergillus niger is a commonly used fungus for large-scale citric acid production.
- Other Aspergillus species, like A. awamori, A. fenicis, A. fonsecaeus, A. luchensis, and others can also produce citric acid. Similar capabilities are shown by some Penicillium species.
- Maintaining stable citric acid production from fungal strains can be challenging due to spontaneous mutations and autolysis during periods of growth. Strategies to mitigate these problems involve periodic strain reisolation from suitable mycelium and avoiding "foggy" patches.
Uses of Citric Acid
- Food Industry: Citric acid is a common food additive used as an acidulant, preservative, buffer, pH stabilizer, fat antioxidant in various food products (like soft drinks, confectionery, jams, jellies, candies) to maintain a tart taste, and in the preservation of colors and flavors.
- Pharmaceutical Industry: Citric acid is used in syrups, astringents, and effervescent tablets and powders, also in blood transfusions.
- Chemical Industry: Citric acid plays a role in water conditioning, metal pickling, as a nontoxic plasticizer in plastic films, and in electroplating, leather tanning, and reactivation of oil wells.
Factors Affecting Citric Acid Production
- Nutrients: Carbohydrate sources (like sucrose, glucose, fructose, maltose, mannose, and starch) are essential. Nitrogen sources (ammonium or nitrate ions), phosphate, low potassium, magnesium and sulfate are also important.
- Inhibitors/Stimulants Specific compounds can influence citric acid production – inhibitors reduce yield, while stimulants might increase it. Methanol and ethanol are important stimulants for Aspergillus niger.
- Temperature: A. niger generally grows optimally at temperatures between 25-30°C. Higher temperatures can negatively impact yield.
- pH: The medium's pH is a critical factor affecting acid production, with 2.5–3.5 being often ideal.
- Aeration and Agitation: Sufficient oxygen is needed for optimal citric acid production by A. niger. Agitation and aeration help with this process.
- Fermentation Time: Fermentation time depends on various factors like the substrate used, the medium's composition, the particular batch or continuous culture setup, and the fermentation conditions during which the citric acid is produced.
Citric Acid Production Processes
- Surface Fermentation: A common method used for citric acid production. This method involves growing the fungus on the surface of a medium.
- Submerged Fermentation: Another method used. A suitable liquid medium containing the components needed for growth and production of citric acid is used.
Recovery Process
- The solutions are filtered to remove calcium sulfate and then decolorized with charcoal and ion exchangers to improve purity.
- The purified solution is then concentrated, and citric acid is crystalized in different forms (anhydrous, monohydrate, or crystalline sodium salt).
- Solvent extraction methods (using solvents like 2-butanol, tributyl phosphate, or amines) can also be employed.
- Techniques for the recovery of citric acid using filtration, crystallization and evaporation methods are described in detail.
Continuous Culture, Fed-Batch Culture, and Solid State Fermentation
- Continuous culture of microbes, with constant feeding and outflow of the medium, can be used for citric acid production.
- Fed-batch fermentation is a continuous input method (feeding a substrate to a batch fermentation), which can be advantageous.
- Solid-state fermentation involves a low-water-activity medium, and commonly contains insoluble solid supports (substrates).
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Description
Explore the fascinating process of citric acid production through biotechnology. Learn about the history, key microorganisms like Aspergillus niger, and the conditions required for optimal yield. This quiz will test your knowledge on the methods and applications of citric acid in various industries.
