Understanding the effects of ionic liquids on enzyme activity and stability

Pretreatment of biomass prior to enzymatic hydrolysis both reduces the amount of enzyme required and increases the yield of sugars.  However, many pretreatment conditions currently in development use harsh conditions leaving the resulting biomass solution incompatible with enzymatic hydrolysis. In particular, ionic liquids have the ability to totally dissolve lignocellulosic biomass, increasing conversion to soluble sugars but either inactivating enzymes or drastically reducing their activity.  Adding ionic liquids affects solution properties including pH, ionic strength, and water activity, and each of these properties can affect enzyme activity.  In this work, we investigate the effects of a set of ionic liquids on both single enzymes and mixtures of enzymes to systematically test the effect of each solution property on enzymatic activity and protein stability.  By examining these individual properties, compatibility guidelines can be developed for ionic liquids that can both pretreat biomass effectively and allow for enzymatic degradation.  In addition to ionic liquid guidlines, enzyme characteristics may be identified that are important for ionic liquid tolerance.  Moving forward, this work serves as a precursor to enzyme engineering studies, by focusing engineering on the properties of the enzyme that are most affected by the ionic liquids.