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Valorization of the Red Seaweed Gracilaria gracilis Through a Biorefinery Approach

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Published on: November 21, 2023

Different regulation of haloperoxidation during agar oligosaccharide-activated defence mechanisms in two related red

Florian Weinberger¹, Boris Coquempot, Sandra Forner

¹Station Biologique, UMR 7139 CNRS-UPMC and LIA DIAMS, BP74, F-29682 Roscoff, France. fweinberger@fm-geomar.de

Journal of Experimental Botany

|January 10, 2008

Summary

Red seaweeds utilize haloperoxidases for halogenation, producing brominated compounds. Elicitation with agar oligosaccharides boosts halogenation in Gracilaria sp. by increasing hydrogen peroxide availability, but not in Gracilaria chilensis.

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Area of Science:

Marine Biology
Biochemistry
Phycology

Background:

Red seaweeds, Gracilaria sp. (Eastern Mediterranean) and Gracilaria chilensis (Chile), possess similar enzymatic machinery for halogenation.
Halogenation in these species is driven by haloperoxidases, dependent on hydrogen peroxide (H(2)O(2)) and vanadate, and inhibited by phosphate and azide.

Purpose of the Study:

To investigate and compare the halogenation mechanisms in Gracilaria sp. and Gracilaria chilensis.
To explore the role of agar oligosaccharide elicitation on halogenation processes and hydrogen peroxide production.

Main Methods:

Enzymatic assays to identify halogenation pathways.
Gel electrophoresis to detect halogenating peroxidases.
Elicitation experiments using agar oligosaccharides to observe changes in halogenation and ion release.

Main Results:

Both species produce bromoform and other brominated halocarbons via vanadate-dependent haloperoxidases.
Elicitation of Gracilaria sp. with agar oligosaccharides significantly increased bromination, iodination, and chlorination, with an eight-fold rise in volatile halocarbons and phenol red bromination.
This increase in Gracilaria sp. is linked to enhanced hydrogen peroxide availability during an oxidative burst, and limited bromide ion release via anion channels.
Agar oligosaccharide oxidation in G. chilensis did not enhance halogenation, suggesting insufficient hypohalous acid generation or lack of H(2)O(2) delivery to the enzyme active site.

Conclusions:

Gracilaria sp. and G. chilensis share fundamental halogenation mechanisms involving vanadate-dependent haloperoxidases.
The oxidative burst response in Gracilaria sp., triggered by agar oligosaccharides, plays a crucial role in enhancing halogenation by increasing H(2)O(2) availability.
Differences in response to agar oligosaccharide oxidation highlight distinct regulatory mechanisms or efficiencies in H(2)O(2) utilization between the two Gracilaria species.