Nitrogen and sulfur requirements for Clostridium thermocellum and Caldicellulosiruptor bescii on cellulosic substrates in minimal nutrient media

► NH4+, urea and glutamine are nitrogen sources for cellulose-grown C. thermocellum. ► Urea (8.3 mM) is sufficient for the fermentation of 0.4% cellulose. ► Both bacteria use sulfate, but produce more oxidized fermentation products. ► Co-cultures grown with both cellulose and xylan were stable with sulfate. ► C. thermocellum grew on defined, minimal medium without reducing ethanol yield.