Fig. 2
Effect of trace elements and N2-sparging on net formate concentration in the culture medium of E. coli strain LW393 and on butyrate production. Strain LW393 was cultured in LB-glucose (50 g l−1). Trace metals (Mo, Ni, Fe and Se) were added as indicated. See “Materials and methods” for other details. a Fermentations started with air in the gas phase. b N2 was sparged through the cultures at 7 ml min−1 throughout the experiment