Production of mixed acids from non-pretreated red algae Gelidium amansii

The present study investigates the production of mixed acids by anaerobic fermentation using non-pretreated red algae Gelidium amansii as a substrate. The production levels of mixed acids were increased 1.6-fold in enrichment cultures of anaerobic digester sludge and tidal field soil compared with fresh sludge. The enrichment culture was composed of four major groups of microbial strains belonging to Clostridium sp. and Enterococcus sp. A defined mixed culture established based on the identified isolates increased mixed acids production level by up to 50.9% (g/g). Semi-continuous fermentation with a biomass-loading rate of 2.77 g/L/d and hydraulic retention time of 30 days yielded a productivity of 1.41 g/L/d. This is the first report of the production of mixed acids from the red algae G. amansii.