Need Oxygen to Breath: Convert Carbohydrates into Alcohol!

“GOLDFISH and their wild crucian carp relatives can survive for five months without breathing oxygen – and now we know how.

The fish carry a set of enzymes that, when oxygen levels drop, helps convert carbohydrates into alcohol that can be released through the gills.

For most animals, including humans, a lack of oxygen can be fatal in minutes. We can metabolise carbohydrates without oxygen, but the process generates toxic
lactic acid that quickly builds up in our bodies.

The carp – and goldfish – have developed a workaround. When they metabolise carbohydrates anaerobically, the end product is alcohol, which is easier to remove.

“The adaptation is very rare among animals,”says Michael Berenbrink at the University of Liverpool in the UK.

Berenbrink and Cathrine Fagernes at the University of Oslo, Norway, and their colleagues discovered that the fish carry an extra set of the enzymes that
specifically helps generate alcohol when metabolism occurs in the absence of oxygen. The enzymes act in essentially the same way as brewer’s yeast.

The adaptation evolved 8 million years ago in the common ancestor of carp and goldfish, via a process known as whole genome duplication. This is when an organism by chance ends up with an extra set of its genes, which can then be repurposed. By making alcohol, crucian carp and goldfish can survive all winter in icy ponds when other fish would suffocate, says Fagernes.” (New Scientist, 2017, p.18).


New Scientist (2017) Goldfish Survive Months Without Oxygen by Brewing Alcohol. New Scientist. 19 August 2017.

Fagernes, C.E., Stensløkken, K-O., Røhr, A.K., Berenbrink, M., Ellefsen, S. & Nilsson, G.E. (2017) Extreme anoxia tolerance in crucian carp and goldfish through neofunctionalization of duplicated genes creating a new ethanol-producing pyruvate decarboxylase pathway. Scientific Reports 7, Article number: 7884 (2017). doi:10.1038/s41598-017-07385-4.


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