Effects of cholinium‐based ionic liquids on Aspergillus niger lipase: Stabilizers or inhibitors

Abstract

Lipases are well‐known biocatalysts used in several industrial processes/applications. Thus, as with other enzymes, changes in their surrounding environment and/or their thermodynamic parameters can induce structural changes that can increase, decrease, or even inhibit their catalytic activity. The use of ionic compounds as solvents or additives is a common approach for adjusting reaction conditions and, consequently, for controlling the biocatalytic activity of enzymes. Herein, to elucidate the effects of ionic compounds on the structure of lipase, the stability and enzymatic activity of lipase from Aspergillus niger in aqueous solutions (at 0.05, 0.10, 0.50, and 1.00 M) of six cholinium‐based ionic liquids (cholinium chloride [Ch]Cl; cholinium acetate ([Ch][Ac]); cholinium propanoate ([Ch][Prop]); cholinium butanoate ([Ch][But]); cholinium pentanoate ([Ch][Pent]); and cholinium hexanoate ([Ch][Hex])) were evaluated over 24 hr. The enzymatic activity of lipase was maintained or enhanced in the lower concentrations of all the [Ch]+‐ILs (below 0.1 M). [Ch][Ac] maintained the biocatalytic behavior of lipase, independent of the IL concentration and incubation time. However, above 0.1 M, [Ch][Pent] and [Ch][Hex] caused complete inhibition of the catalytic activity of the enzyme, demonstrating that the increase in the anionic alkyl chain length strongly affected the conformation of the lipase. The hydrophobicity and concentration of the [Ch]+‐ILs play an important role in the enzyme activity, and these parameters can be controlled by adjusting the anionic alkyl chain length. The inhibitory effects of [Ch][Pent] and [Ch][Hex] may be of great interest to the pharmaceutical industry to induce pharmacological inhibition of gastric and pancreatic lipases.

An Overview on the Recent Advances in Alternative Solvents as Stabilizers of Proteins and Enzymes

“…In this context, Nascimento et al [77] further investigated the stability and activity of A. niger lipase in aqueous solutions of six cholinium-based ILs (…”

Utilization of Clay Materials as Support for Aspergillus japonicus Lipase: An Eco-Friendly Approach

“…In a hydrophobic or non-aqueous environment, the hydrophobic layer triggers the opening of the "lid", allowing the entry of the substrate into the active site, whereas in aqueous environments the lipase remains inactive [70,71]. Thus, the enzymatic activity of the lipases that contain the "lid" is controlled by the cap domain [71,72]. Thus, immobilization process on hydrophobic supports allows the immobilization of the open conformation of the lipase, improving its enzymatic activity, causing the enzyme to hyperactivate [66,[73][74][75].…”

Deep Eutectic Solvents for Innovative Pharmaceutical Formulations

“…Aspergillus niger was investigated by Nascimento et al (Nascimento et al, 2019). At low concentrations, all the ionic liquids tested (choline, choline acetate, choline propanoate, choline butanoate, choline pentanoate and choline hexanoate) allowed the activity to be maintained, or even enhanced.…”

“…It has also been demonstrated in work cited above that the activity of many enzymes can be conserved or even improved in deep eutectic solvents, opening up the way to their use as alternative media for biotransformations. Thus the thermal stability of lysozyme can be increased (Su and Klibanov, 2015), the catalytic activity of catalase (Harifi-Mood et al, 2017), laccase (Khodaverdian et al, 2018) and lipase (Nascimento et al, 2019) was conserved and the biotransformation of steroids by bacteria was efficient (Mao et al, 2019). Finally, Sivapragasam et al have shown that some choline-based ionic liquids promoted the growth of the yeast Saccharomyces cerevisiae, suggesting that deep eutectic solvents could act as an alternative medium for microbial cultures (Sivapragasam et al, 2019).…”