Bioconversion of Capsaicin by Aspergillus oryzae

Area of Science:

• Microbiology
• Food Science
• Biochemistry

Background:

• Capsaicin, the pungent compound in chili peppers, is a key component in traditional fermented foods like Korean gochujang.
• Aspergillus oryzae is widely used in food fermentation, particularly for gochujang production.
• Understanding microbial biotransformation of capsaicin is crucial for food quality and safety.

Purpose of the Study:

• To identify and characterize capsaicin metabolites produced by Aspergillus oryzae.
• To confirm and quantify these metabolites in gochujang.
• To elucidate the biotransformation pathways involved.

Main Methods:

• Incubation of capsaicin with Aspergillus oryzae in potato dextrose broth.
• Purification of metabolites using ethyl acetate extraction.
• Structural identification of metabolites via Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS).
• Quantification in gochujang using Liquid Chromatography-Electrospray Ionization Mass Spectrometry (LC-ESI-MS).

Main Results:

• Capsaicin concentration decreased while new metabolites increased during incubation.
• Five capsaicin metabolites were identified: N-vanillylcarbamoylbutyric acid, N-vanillyl-9-hydroxy-8-methyloctanamide, ω-hydroxycapsaicin, 8-methyl-N-vanillylcarbamoyl-6(E)-octenoic acid, and 2-methyl-N-vanillylcarbamoyl-6(Z)-octenoic acid.
• These metabolites were confirmed and quantified in gochujang samples.

Conclusions:

• Aspergillus oryzae effectively bioconverts capsaicin.
• Proposed metabolic pathways include ω-hydroxylation, alcohol oxidation, hydrogenation, isomerization, and α-/β-oxidation.
• The findings provide insight into capsaicin degradation during gochujang fermentation.