Energy-Saving Pretreatments Affect Pelagic Sargassum Composition and DNA Metabarcoding Analysis Reveals the Microbial Community Involved in Methane Yield

Abstract

Sargassum spp. floods the Caribbean coastlines, causing damage to the local economy and environment. These macroalgae have a low methane yield that makes the anaerobic digestion (AD) process unviable, so low-cost pretreatments are required. This research investigated the efficiency of energy-saving pretreatments, such as water washing, that had not been evaluated for these species. The microbial communities involved in AD of the best and worst-performing systems were also analyzed by high-throughput sequencing. The results showed that water washing pretreatment modified the content of inorganic compounds, fibers, and C:N ratio and increased the methane yield by 38%. The bacterial phyla Bacteroidota, Firmicutes, and Thermotogota, as well as the archaea genera Methanosarcina, RumEn_M2, and Bathyarchaeia, dominated the microbial communities. This study is the first to show the microbial community structure involved in the AD of Sargassum spp. The pretreatments presented in this study may help overcome the previously reported limitations.