Ionic Liquids Increase the Catalytic Efficiency of a Lipase (Lip1) From an Antarctic Thermophilic Bacterium

Abstract

Lipases catalyze the hydrolysis and synthesis of triglycerides and their reactions are widely used in industry. The use of ionic liquids has been explored in order to improve their catalytic properties. However, the effect of these compounds on kinetic parameters of lipases has been poorly understood. A study of the kinetic parameters of Lip1, the most thermostable lipase from the supernatant of the strain ID17, a thermophilic bacterium isolated from Deception Island, Antarctica, and a member of the genus Geobacillus is presented. Kinetic parameters of Lip1 were modulated by the use of ionic liquids BmimPF6 and BmimBF4. The maximum reaction rate of Lip1 was improved in the presence of both salts. The highest effect was observed when BmimPF6 was added in the reaction mix, resulting in a higher hydrolytic activity and in a modulation of the catalytic efficiency of the enzyme. However, the catalytic efficiency did not change in the presence of BmimBF4. The increase of the reaction rates of Lip1 promoted by these ionic liquids could be related to possible changes in the Lip1 structure. This effect was measured by quenching of tryptophan fluorescence of the enzyme, when it was incubated with each liquid salt. In conclusion, the hydrolytic activity of Lip1 is modulated by the ionic liquids BmimBF4 and BmimPF6, improving the reaction rate and the catalytic efficiency of this enzyme when BmimPF6 was used. This effect is probably due to changes in the structure of Lip1 induced by the presence of these ionic liquids, stimulating its catalytic activity.

Whole-Cell Biocatalytic Processes with Ionic Liquids

“…24 In some cases, IC 50 (the concentration of chemical at which cell growth, cell viability or metabolism is inhibited at 50%) was measured in order to quantify the toxicity of ILs. As shown in 6 ] was toxic towards the growth of E. coli at concentration as low as 0.5% (v/v), while no toxic effects were found by Pfruender et al 20 at a concentration of 20% (v/v) for the same species of microorganism. One important factor that may differ between these studies and may at least in part explain the contrasting results is that the concentration of biomass differs, and toxic effects may be more obvious in a low biomass concentration than in a higher one.…”

“…1a). It was shown that room-temperature ILs, such 6 ], can be successfully used in place of conventional solvents for the Rhodococcus R312-catalyzed biotransformation of 1,3-DCB in an aqueous/IL biphasic system. The substrate 1,3-DCB has very low aqueous solubility, but a high partition coefficient in the IL and organic phase.…”

“…However, the initial rate of production of 3-CB in the water-[BMIm][PF 6 ] system was 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 slower than that in water-toluene system, due to the reduced rate of mass transfer of 1,3-DCB from the viscous IL phase. It was also shown that the specific activity of the biocatalyst in the water-[BMIm] [PF 6 ] system was greater than in a water-toluene system. This suggested that the rate of production of 3-CB was limited by mass transfer of the substrate rather than by the activity of the biocatalyst.…”

“…[BMIm][PF 6 ] was employed in an IL-aqueous biphasic system. Under the optimal conditions, the substrate conversion was up to 95.5% (compared to 68.6 % in aqueous buffer) and the product e.e.…”

“…3 Applications of ILs in biotransformations have been extensively studied during the past decade, with a strong focus on catalysis using isolated enzymes, which remain active in ILs and exert good performance. [4][5][6] The beneficial effects of ILs on enzymatic activity and selectivity are partly attributed to the high polarity of these solvents, with ability to increase the solubility of polar substrates while the biocatalyst exhibits high activity. [7][8][9] And the influence of ILs on the structure, activity, stability and selectivity of isolated enzymes, as well as the applications of enzymes in such media have been extensively reviewed.…”