Effect of deep eutectic solvent mixtures on lipase activity and stability

• DES mixtures have many potential applications as protein activators or stabilizers.
• DES mixtures as cosolvents enhanced the activity and stability of Candida rugosa lipase.
• Solvatochromic parameters of DESs were determined and correlated with the stability of lipase.

DESs (deep eutectic solvents) have many potential applications as cosolvents or anhydrous reaction media for biocatalytic reactions, owing to their non-volatility, non-flammability, non-toxicity, biocompatibility, biodegradability, and low cost. In this work, choline chloride ([Ch]Cl)-based DESs and DES mixtures containing two hydrogen bond donors were used as cosolvents to enhance the activity and stability of Candida rugosa lipase in aqueous reactions. The activity of lipase in an aqueous solution of [Ch]Cl:urea:glycerol was 155% higher than that in buffer. The half-life time of lipase at 40 °C in an aqueous solution of [Ch]Cl:glycerol was enhanced by 9.2 times. The lipase showed the highest acid stability and base stability in the aqueous solutions of [Ch]Cl:glycerol:thiourea and [Ch]Cl:ethylene glycol:formamide, respectively. In general, glycerol-containing DES mixtures were very useful in enhancing the activity and stability of lipase, while formamide-containing DES mixtures could not efficiently enhance the activity and stability of lipase. To understand the effect of DES mixtures on the activity and stability of lipase in aqueous solution, four solvatochromic parameters of DES mixtures were determined. When the solvatochromic parameters of DES mixtures were correlated with the stability of lipase in aqueous solutions of DES mixtures, it was found that thermal stability and storage stability of lipase were associated with the hydrogen bond acidity of DES mixtures. Acid stability and base stability of lipase were correlated with polarity based on Reichardt’s dye and the dipolarity/polarizability of DES mixtures, respectively.

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