Fermentation of lignocellulosic hydrolysates. II: inhibitors and mechanisms of inhibition

During hydrolysis of lignocellulosic materials a wide range of compounds which are inhibitory to microorganisms are formed orreleased. Based on their origin the inhibitors are usually divided in three major groups: weak acids, furan derivatives, and phenolic compounds. These compounds limit e_cient utilisation of the hydrolysates for ethanol production by fermentation. If the inhibitors are identi®ed and the mechanisms of inhibition elucidated, fermentation can be improved by developing speci®c detoxi®cation methods, choosing an adapted microorganism, or optimising the fermentation strategy. The present review discusses the generation of inhibitors during degradation of lignocellulosic materials, and the e.ect of these on fermentation yield and productivity. Inhibiting mechanisms of individual compounds present in the hydrolysates and their interaction e.ects are reviewed.