The genus
Asparagopsis is a prolific source of halogenated metabolites. Due to its commercial applications, it has been intensively cultivated in
southern Portugal. In the present study, we assess if the internal levels of the major halogenated metabolites (bromoform
and dibromoacetic acid) in
Asparagopsis taxiformis can be increased with hydrogen peroxide (H
2O
2) addition. Previous studies with red algae showed that the production/release of bromoform can be enhanced by exogenously
supplying H
2O
2. However, no study has assessed if H
2O
2 supply enhances the content of secondary metabolites within the biomass. This detail is important as the objective of the
proposed research is to enhance the content of these valuable metabolites in the produced biomass. Both the activity of the
haloperoxidase enzyme and the metabolite content were assessed on short-term and long-term incubation periods to H
2O
2. To determine the susceptibility of
A. taxiformis photosynthetic performance to the imposed oxidative stress, the in vivo fluorescence of photosystem II was monitored.
A. taxiformis was shown to be physiologically vulnerable to H
2O
2, given the observed decrease of the maximum quantum yield of photosynthesis (
F
v/
F
m). Contrary to what was expected, the presence of H
2O
2 inhibited the activity of the iodoperoxidase enzyme. Nevertheless, the extracted halogenated metabolites were higher over
the first hours of exposure to H
2O
2, decreasing after 48 h. These results are probably related to the prosthetic group of the halogenated enzyme in
A. taxiformis and the long-term oxidative stress damage of H
2O
2 exposure. Considering the objective of the proposed research, addition of H
2O
2 to the cultures, prior (3 h) to biomass harvesting, increases the metabolite content.
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