Adaptation of a microbial consortium to pelagic Sargassum modifies its taxonomic and functional profile that improves biomethane potential

Abstract

Abstract In recent years, pelagic Sargassum has invaded the Caribbean coasts, and anaerobic digestion has been proposed as a sustainable management option. However, the complex composition of these macroalgae acts as a barrier to microbial degradation, thereby limiting methane production. Microbial adaptation has emerged as a promising strategy to improve substrate utilization and stress tolerance. This study aimed to investigate the adaptation of a microbial consortium to enhance methane production from the pelagic Sargassum. Microbial adaptation was carried out for 100 days by progressively feeding Sargassum. The evolution of the microbial community was analyzed by high-throughput sequencing of 16S rRNA amplicons. Additionally, 16S rRNA data were used to predict functional profiles using the iVikodak platform. The results showed that, after adaptation, the consortium was dominated by the bacterial phyla Bacteroidota, Firmicutes, and Atribacterota, as well as methanogens of the families Methanotrichaceae and Methanoregulaceae. The abundance of genes related to different metabolism-related functions decreased on day 60 when the Sargassum concentration increased. However, after 100 d, the functions increased again, enhancing methane production. The adapted consortium (AC) exhibited a biomethane potential of 160.03 ± 4.64 N-mL g− 1 VS and a biodegradability index of 39%, representing a 60% improvement. Additionally, the degradation kinetics and methane production of pelagic Sargassum were improved. The study concludes that microbial adaptation enhances the bioconversion of pelagic Sargassum into methane. It is also suggested that a microbial consortium should be generated to achieve greater efficiency in the bioconversion of Sargassum, along with other pretreatments.