Generation of volatile fatty acids by axillary bacteria

Area of Science:

• Microbiology
• Biochemistry
• Dermatology

Background:

• Axillary malodor is primarily caused by short-chain volatile fatty acids (VFAs; C(2)-C(5)).
• Bacterial biotransformation of natural skin secretions generates these odorous VFAs.
• The specific biochemical origins of VFAs on axillary skin remain largely uncharacterized.

Purpose of the Study:

• To investigate the biochemical pathways for VFA generation from substrates found on axillary skin.
• To identify the bacterial species responsible for producing VFAs.
• To elucidate the origins of VFA-based axillary malodor.

Main Methods:

• Development of assay systems to study VFA generation.
• Incubation of bacterial cultures (Propionibacteria, Staphylococci, Corynebacteria) with potential substrates like glycerol, lactic acid, and amino acids.
• Analysis of VFA production using in vitro kinetic data.

Main Results:

• Propionibacteria and staphylococci ferment glycerol and lactic acid to acetic and propionic acids (C(2)-C(3) VFAs).
• Staphylococci convert branched amino acids (e.g., leucine) to branched VFAs (e.g., isovaleric acid, C(4)-C(5)).
• A specific subgroup of Corynebacterium (Corynebacteria A) significantly contributes to axillary VFA levels through fatty acid biotransformations, exceeding the contribution of other identified pathways.

Conclusions:

• The study elucidates key biochemical origins of VFAs responsible for axillary malodor.
• Identified bacterial fermentation and biotransformation pathways provide novel insights into malodor generation.
• Findings pave the way for developing targeted, novel deodorant systems based on inhibiting specific VFA production pathways.