Acetaldehyde production and metabolism by human indigenous and probiotic Lactobacillus and Bifidobacterium strains

Many human gastrointestinal facultative anaerobic and aerobic bacteria poss ess alcohol dehydrogenase (ADH) activity and are therefore capable of oxidi zing ethanol to acetaldehyde. We examined whether human gastrointestinal la ctobacilli (three strains), bifidobacteria (five strains) and probiotic Lac tobacillus GG ATCC 53103 are also able to metabolize ethanol and acetaldehy de in vitro. Acetaldehyde production by bacterial suspensions was determine d by gas chromatography after a 1-h incubation with 22 mM ethanol. To deter mine the acetaldehyde consumption, the suspensions were incubated with 50 m uM or 500 muM acetaldehyde as well as with 500 muM acetaldehyde and 22 mM e thanol, i.e. under conditions resembling those in the human colon after alc ohol intake. The influence of growth media and bacterial concentration on t he ability of lactobacilli to metabolize acetaldehyde and to produce acetat e from acetaldehyde were determined. ADH and aldehyde dehydrogenase (ALDH) activities were determined spectrophotometrically. Neither measurable ADH n or ALDH activities were found in aerobically grown Lactobacillus GG ATCC 53 103 and Lactobacillus acidophilus ATCC 4356 strains. All the lactobacilli a nd bifidobacteria strains revealed a very limited capacity to oxidize ethan ol to acetaldehyde in vitro. Lactobacillus GG ATCC 53103 had the highest ac etaldehyde-metabolizing capacity, which increased significantly with increa sing bacterial concentrations. This was associated with a marked production of acetate from acetaldehyde. The type of the growth media had no effect o n acetaldehyde consumption. Addition of ethanol to the incubation media dim inished the acetaldehyde-metabolizing capacity of all strains. However, in the presence of ethanol, Lactobacillus GG ATCC 53103 still demonstrated the highest capacity for acetaldehyde metabolism of all strains. These data su ggest a beneficial impact of Lactobacillus GG ATCC 53103 on high gastrointe stinal acetaldehyde levels following alcohol intake. The possible clinical implications of this finding remain to be established in in vitro studies.