α-Rhamnosidase and β-glucosidase expressed by naringinase immobilized on new ionic liquid sol-gel matrices: Activity and stability studies

Novel ionic liquid (IL) sol-gel materials development, for enzyme immobilization, was the goal of this work. The deglycosylation of natural glycosides were performed with α-l-rhamnosidase and β-d-glucosidase activities expressed by naringinase. To attain that goal ILs with different structures were incorporated in TMOS/Glycerol sol-gel matrices and used on naringinase immobilization. The most striking feature of ILs incorporation on TMOS/Glycerol matrices was the positive impact on the enzyme activity and stability, which were evaluated in fifty consecutive runs. The efficiency of α-rhamnosidase expressed by naringinase TMOS/Glycerol@ILs matrices increased with cation hydrophobicity as follows: [OMIM]>[BMIM]>[EMIM]>[C(2)OHMIM]>[BIM] and [OMIM]≈[E(2)-MPy]≫[E(3)-MPy]. Regarding the imidazolium family, the hydrophobic nature of the cation resulted in higher α-rhamnosidase efficiencies: [BMIM]BF(4)≫[C(2)OHMIM]BF(4)≫[BIM]BF(4). Small differences in the IL cation structure resulted in important differences in the enzyme activity and stability, namely [E(3)-MPy] and [E(2)-MPy] allowed an impressive difference in the α-rhamnosidase activity and stability of almost 150%. The hydrophobic nature of the anion influenced positively α-rhamnosidase activity and stability. In the BMIM series the more hydrophobic anions (PF(6)(-), BF(4)(-) and Tf(2)N(-)) led to higher activities than TFA. SEM analysis showed that the matrices are shaped lens with a film structure which varies within the lens, depending on the presence and the nature of the IL. The kinetics parameters, using naringin and prunin as substrates, were evaluated with free and naringinase encapsulated, respectively on TMOS/Glycerol@[OMIM][Tf(2)N] and TMOS/Glycerol@[C(2)OHMIM][PF(6)] and on TMOS/Glycerol. An improved stability and efficiency of α-l-rhamnosidase and β-glucosidase expressed by encapsulated naringinase on TMOS/Glycerol@[OMIM][Tf(2)N] and TMOS/Glycerol@[C(2)OHMIM][PF(6)] were achieved. In addition to these advantageous, with ILs as sol-gel templates, environmental friendly processes can be implemented.