Kojic Acid: Production and Uses

Study Notes

Kojic Acid: Production and Applications

Kojic acid is an organic compound produced by certain fungi like Aspergillus oryzae.
Historically, it was discovered as a byproduct of rice fermentation in sake production.
Chemical properties:
- Molecular formula: C6H6O4
- Molecular weight: 142.11 g/mol
- Colorless, prismatic needles
- Melting point: 150-160°C
- Soluble in polar solvents like water and ethanol.
Kojic acid production:
- Fungal strains: Aspergillus oryzae, A. glaucus, A. flavus, A. awamori and others.
- Bacterial strains: Several species of Acetobacter.
- Carbon sources: Starch, dextrins, sucrose, maltose, glucose (best source), fructose, mannose, galactose, xylose, and arabinose.
- Optimal fermentation conditions:
  - pH: 2-5
  - Temperature: 30-35°C
  - Incubation period: 9-20 days
Kojic acid detection:
- Crystals: Kojic acid crystals can be obtained by storing culture filtrate in a refrigerator at 5°C overnight.
- Ferric chloride test: It forms an intense red color with Ferric Chloride.
Factors influencing Kojic acid production:
- Ethylene chlorohydrin: A concentration of 100 mg/L increases yields.
- Inhibitors: Oxalic, citric, hydrochloric, and nitric acids inhibit production.
- Temperature manipulation: Lowering the temperature after 5 days of incubation can increase yields.
- Duration of fermentation: Typically 9-20 days, depending on factors like substrate, mold species, temperature, and pH.
Biosynthesis of Kojic acid:
- Two pathways are known:
  - Usual route: Dehydratase enzymes convert glucose to kojic acid.
  - Pentoses pathway: Dihydroxyacetone acts as an intermediate.
Applications of Kojic acid:
- Food preservation:
  - Prevents browning in cut fruits.
  - Preserves pink and red colors in seafood.
- Cosmetics: Used for skin whitening.
- Antimicrobial properties: Exhibits antibacterial and antifungal activity.
- Anticancer activity: Cocrystals with quercetin show enhanced cytotoxic activity against cancer cells.
- Radioprotective effects: Offers protection against radiation-induced damage.
- Analytical reagent: Forms a bright red complex with ferric ions, useful for iron analysis.
- Other medicinal properties: Antibiotic, painkiller, anti-inflammatory, anti-diabetic, and insecticide properties.
- Industrial uses: Serves as an intermediate for metal chelate production.
- Food and cosmetics: Used to preserve or modify colors of substances.
Kojic acid products: Widely used in skin whitening products.