Acetaldehyde Production by Strains Used as Probiotics in Fermented Milk.

Area of Science:

• Microbiology
• Biochemistry

Background:

• Acetaldehyde is a key metabolite in carbohydrate, protein, and nucleic acid pathways.
• Lactic acid bacteria (LAB) possess diverse metabolic routes for acetaldehyde.
• Understanding LAB acetaldehyde metabolism is crucial for microbial physiology and biotechnology.

Purpose of the Study:

• To investigate and compare the acetaldehyde metabolism pathways in Lactobacillus acidophilus and Lactobacillus casei strains.
• To identify specific enzyme activities related to acetaldehyde formation and degradation in these LAB species.
• To determine the factors contributing to acetaldehyde accumulation in the growth medium.

Main Methods:

• Isolation of Lactobacillus acidophilus and Lactobacillus casei strains from healthy children's feces.
• Enzyme activity assays for phosphotransacetylase, acetate kinase, aldehyde dehydrogenase, 2-deoxiribose aldolase, α-carboxylase, threonine aldolase, and phosphoketolase.
• Analysis of acetaldehyde accumulation in growth media.

Main Results:

• Both L. acidophilus and L. casei exhibited phosphotransacetylase, acetate kinase, aldehyde dehydrogenase, and 2-deoxiribose aldolase activities.
• α-Carboxylase and threonine aldolase activities were specific to L. acidophilus.
• Phosphoketolase activity was present in L. casei but absent in L. acidophilus.
• Acetaldehyde accumulated in the growth medium due to higher formation than degradation enzyme activities.

Conclusions:

• Lactobacillus species display distinct enzymatic profiles for acetaldehyde metabolism.
• Differences in enzyme activities explain the observed variations in acetaldehyde accumulation.
• These findings contribute to understanding LAB metabolic diversity and potential biotechnological applications.