SargBiome

Project Title

Pelagic Sargassum microbiomes and its role in nutrient turnover, decomposition and potential application for bioethanol production.

SHORT DESCRIPTION OF THE PROJECT 

The brown seaweed pelagic Sargassum has gained global attention in the last decade due to the massive beaching events occurring on both sides of the Atlantic. Numerous local initiatives and companies are trying to valorize its biomass by creating valuable products such as bioethanol that can be used both as a precursor for sustainable plastics or as biofuel. However, attempts to ferment Sargassum using commercial yeasts have previously resulted in very low yields. Even though there are a few studies describing Sargassum microbiomes, no information is available regarding the function of the microorganisms growing on Sargassum and their role in providing nutrients or degrading it. One hypothesis is that its microbiome provides Sargassum with extra nutrients enabling it to grow fast in oligotrophic waters. Furthermore, Sargassum excretes a high percentage of carbon as dissolved organic carbon (DOC). Part of this excreted carbon has been hypothesized to be recalcitrant and therefore contribute to long-term carbon sequestration in the ocean. 

SargBiome aims to elucidate the biodiversity of microorganisms growing on healthy and degrading Sargassum, assess their potential to provide the algae with nutrients via nitrogen fixation or iron chelation, and to degrade its biomass and excreted DOC. Through a combination of field sampling, lab experiments, and metagenomic analysis, the PhD candidate will characterise the biodiversity and functions of Sargassum microbiomes and isolate marine yeasts capable of biodegrading Sargassum through fermentation producing bioethanol. This thesis will not only advance our basic understanding of the ecology of this relevant macroalgae, but it will also provide crucial knowledge to the nascent blue economy sector. 

 

HYPOTHESES AND OVERARCHING GOALS

The overarching goal of SargBiome is to shed light on the role of the microbiome of pelagic Sargassum on its growth and decomposition to deliver important knowledge to industry PROGRAM MANAGEMENT - VERSION 1 2 INSP-2024 (V) Project proposal on its potential for carbon sequestration and a source for sustainable products for the blue bioeconomy. 

The hypotheses of SargBiome are: 

  1. The biodiversity of pelagic Sargassum microbiomes changes depending on its status: free floating in oligotrophic waters, free-floating in nutrient replete waters and degrading on the beach.
  2. Sargassum microbiomes include nitrogen fixers and iron chelating bacteria that can increase its growth.
  3. A high percentage of the dissolved organic carbon excreted by Sargassum is recalcitrant and cannot be degraded by its microbiome or surrounding pelagic microorganisms leading to permanent carbon sequestration. 

  4. Marine yeasts isolated from degrading Sargassum microbiomes are more efficient at producing bioethanol through fermentation than commercial yeasts.