Identification of suitable ionic liquids for application in the enzymatic hydrolysis of rutin by an automated screening

An automated method in milliliter scale was developed for the screening of process parameters concerning the hydrolysis of the flavonoid rutin catalyzed by the rhamnosidase activity of naringinase from Penicillium decumbens. Besides the effect of additives such as ionic liquids and low molecular salts, the productivity in a multiple phase system as well as the recyclability of the enzyme in repetitive batches were studied. The hydrophobic ionic liquid (IL) trihexyl(tetradecyl)phosphonium bis(trifluormethylsulfonyl)imide P(h₃)t]Tf₂N] was identified to combine the most favorable characteristics out of 23 investigated ILs with regard to enzyme compatibility, substrate solubility and enzyme partition coefficient. Also, for the corresponding cations 1-ethyl-3-methylimidazolium EMIM], 1-butyl-3-methylimidazolium BMIM], 1-butyl-1-methylpyrrolidinium BMPL] and 1-octyl-3-methylimidazolium OMIM], the entity with the Tf₂N] anion was best tolerated by the naringinase. With increasing IL content, higher space time yields with up to 1.5 g/(L h) for 80% (v/v) P(h₃)t]Tf₂N] were achieved. Enhanced specific enzyme activity was observed in the presence of Ca²⁺ ions. By addition of P(h₃)t]Tf₂N] and calcium chloride, the reactive aqueous phase was successfully used in three repetitive batches with full conversion.