Several strains of solvent-producing clostridia were investigated for their ability to produce solvents front unsupplemented potato and front potato that had been pre-hydrolysed with antylolytic enzymes. Most of the strains were strongly, solventogenic and prior treatment with the enzymes gave no improvement in this property. C. acetobutylicum DSM 1731 showed a reactor productivity of 0.24 g/l/h on unhydrolysed potato, and was the most productive strain tested. In contrast, C. acetobutylicum ATCC 824 was only weakly solventogenic unless the potato was pre-hydrolysed using amylolytic enzymes.