Stimulation of Laccase Biocatalysis in Ionic Liquids: A Review on Recent Progress

It has been well known that laccases can directly or indirectly catalyze oxidation of a broad species of phenols, amines and many other electron donor substrates. However, laccases as biocatalyst in "green" ionic liquids (ILs) media instead of conventional solvents are less known and regarded as an innovative research direction. The presence of ILs can either inhibit or stimulate laccase activity, strongly depending on water-miscibility and kosmotropic natures of ILs. In addition, enzyme source, mediator, pH as well as water content are very important factors which influence laccase activity and stability. Therefore, elucidation of mechanisms underlying the interactions between laccases and ILs will facilitate to screen ILs with excellent laccase compatibility. Strategies based on molecular evolution, enzyme immobilization and/or ILs modification greatly increase the tolerance of laccases against specific ILs. The use of ILs can spread the laccase applications in fields of biosynthesis, biodegradation, biosensor and biofuel cells. This article summarizes the recent progress, trends and problems in this field and focuses, in particular, on the stimulation of laccase activity in aqueous ILs media.