Concentration effect of hydrophilic ionic liquids on the enzymatic activity of Candida antarctica lipase B

Abstract

A systematic study of the effects of hydrophilic ionic liquids concentration and nature (alkyl chain length and type of anion) on the activity of Candida antarctica lipase B is here reported. The increase in the concentration of the studied ionic liquids is shown to cause a decrease of the enzyme activity, but the effect is dependent on the ionic liquid used. This behavior is partially due to the ionic liquid impact on the thermodynamic water activity, but direct interactions between the hydrophilic ionic liquid and the enzyme are also disclosed. Cations with longer alkyl chains decrease the enzyme activity by obstruction of its non-polar active site, while direct interactions established between the enzyme and the anions, dominated by dispersion forces and hydrogen-bonding, contribute also for the loss of activity observed.

Evaluating Self-buffering Ionic Liquids for Biotechnological Applications

“…19,51 Therefore, in order to examine the viability of selfbuffering GB-ILs as media for enzyme applications, the enzyme activity and stability 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 biocatalyst in biotechnological applications due to its multiplicity of catalytic applications. 41,[52][53] As depicted in Figure 3 1 2 3 4 5 6 7 8 9 1...…”

Chemical Pretreatment Methods for the Production of Cellulosic Ethanol: Technologies and Innovations

“…For example, chloride-based ILs such as 1-butyl-3-methylimidazolium chloride (Bmim-Cl) are toxic, corrosive, and very hygroscopic, while others such as Amim-Cl are viscous with reactive side chains [172]. Also, ILs with long akyl chains have the tendency to obstruct nonpolar active sites of enzymes due to their hydrophobic nature [173]. Others have favourable properties and have thus been under intense investigation as promising solvents.…”

“…The effectiveness of pretreatment is predicted using the Kamlet-Taft hydrogen bond acceptor ability, : usually, the higher values of translate to higher lignin removal and vice versa [177]. It is known that component ions in ILs influence enzyme activity [178] and stability [173], and the anion-as a result of its hydrogen basicity-attacks and breaks the hydrogen bonds of cellulose structure [179] by forming hydrogen bonds with the cellulose [180]. Thus, the cellulose is solubilised and the crystalline nature is reduced [181] via cell wall swelling resulting from dislocation of hydrogen bonds between cellulose fibrils and lignin [182], partial removal of hemicellulose, and biomass delignification [183].…”

“…Moreover, the separation of hydrophilic ILs and monomeric sugars in water is difficult [178,204]. Some ILs also exhibit tendencies to denature enzymes [168] and the active sites of enzymes could be blocked by layers of hydrophilic ILs, decreasing or destroying the aqueous phase surrounding enzyme surface [173]. Washing of regenerated cellulose as well as recycling of ILs via processes such as evaporation and reverse osmosis is practically costly which presents challenges in the development of process technologies for the efficient use of ILs within a biorefinery.…”

Expression and Biochemical Characterization of a Thermophilic Organic Solvent-Tolerant Lipase from Bacillus sp. DR90

“…Among Br-containing ILs, [HMIm][Br] showed the most stimulatory effect on enzyme activity. Usually, as the chain length of the alkyl substituent on the imidazolium ring of the cation increases and the anion size decreases, the lipase activity would increase [31]. The rates of lipolytic reaction are similar to or higher than those observed in organic solvents.…”