Various marine sediments were evaluated as promising microbial sources for methane fermentation of
Saccharina japonica, a brown alga, at seawater salinity. All marine sediments tested produced mainly acetate
among volatile fatty acids. One marine sediment completely converted the produced volatile fatty
acids to methane in a short period. Archaeal community analysis revealed that acetoclastic methanogens
belonging to the Methanosarcina genus dominated after cultivation. Measurement of the specific conversion
rate at each step of methane production under saline conditions demonstrated that the marine sediments
had higher conversion rates of butyrate and acetate than mesophilic methanogenic granules.
These results clearly show that marine sediments can be used as microbial sources for methane production
from algae under high-salt conditions without dilution