Phylogenetic and functional characterization of the microbiome of Sargassum seaweed waste

In order to utilize seaweed waste as a feedstock in biorefinery, it is essential to characterize the microbial communities and their metabolic processes in seaweed decomposition. In this study, the phylogeny and functionality of the prokaryotic and fungal microbiome of Sargassum seaweed waste that has inundated the Barbados coast were assessed for the first time by targeting the 16S rRNA gene and internal transcribed spacer (ITS) region of ribosomal RNA, respectively, using the cultivation-independent Illumina next-generation sequencing approach. The resulting 67 032 and 91 085 high-quality paired-end reads of 16S rRNA gene and ITS were assigned to 734 and 179 amplicon sequence variants (ASVs), respectively. The predominant bacterial genera recorded were Muricauda, Aminobacterium, Mesorhizobium, Marinobacter, Reichenbachiella, Hyphomonas, Simiduia, Aquamicrobium, Oceanicola and Alcanivorax. The major genera of Archaea belonged to Methanosarcina, Methanogenium and Methanosaeta, and that of fungi to Sigmoidea, Tylopilus and Mucor. The metabolic functions of the Sargassum metagenome, analysed via PICRUSt, revealed the predominant metabolic pathways related to the biosynthesis of terpenoids and polyketides, the biosynthesis of other secondary metabolites, the metabolism of cofactors and vitamins, and the xenobiotic biodegradation. Furthermore, the prevalence of diverse alginate lyase-producing bacteria suggests that Sargassum waste is an ideal niche material for the isolation of potent microbial biocatalysts to sustainably depolymerize alginate and thereby produce third-generation biofuels and bioactive alginate oligosaccharides with novel industrial applications.