SUMMARY: In order to turn ethanol into acetaldehyde, the enzyme alcohol dehydrogenase requires both a zinc atom and NAD+. This study looks at the levels of NAD+ in Lactobacillus and Bifidobacteria after incubating them in ethanol and acetaldehyde, in vitro. Results showed that both bacteria weren’t that efficient at turning ethanol into acetaldehyde, but were better at metabolizing acetaldehyde.
LESSON COMMENTS: These experiments were conducted in vitro, and not in vivo. Bacteria were grown in test tubes and then ethanol or acetaldehyde was added into the medium. We can try to make some reasonable connections as to how these bacteria will behave in our colon, but it would only be speculation.
Be aware: the graphs in this paper have different values on the X-axis.
Under the discussion section, E. Coli and its abilities to metabolize ethanol and acetaldehyde are discussed but the results are not part of the graphs. Articles on E. Coli metabolism of ethanol and acetaldehyde are cited in the paper and may be a good way to encourage further research.
This is also a good article to talk about the role of NAD+ in both cellular respiration and acetaldehyde break down. Students should be able to talk about the role of electrons, zinc metal (why is this needed), and redox reactions. A further question to ask students is: What happens to cellular respiration if there’s a need for NAD+ during alcohol and acetaldehyde metabolism?
Bogoslovsky, Tanya & Jousimies-Somer, H & Jokelainen, K & Heine, R & Salaspuro, Mikko. (2000). Acetaldehyde production and metabolism by human indigenous and probiotic Lactobacillus and Bifidobacterium strains. Alcohol and alcoholism (Oxford, Oxfordshire). 35. 561-8. 10.1093/alcalc/35.6.561.