The correlation between the physicochemical properties of water-based deep eutectic solvents and catalytic activity of lipase Novozym 435

Abstract

With its unique physicochemical properties, deep eutectic solvents (DESs) can efficiently regulate the effect of enzyme activity. The present study investigated the correlation between catalyzed synthesis activity of lipase N435 and physicochemical (conductivity, surface tension, pH and viscosity) properties of several choline chloride (ChCl)-based DESs, ChCl: urea, ChCl: ethylene glycol and ChCl: glycerol in the molar ratio of 1:2, respectively at a specific temperature and water content range. The results revealed that conductivity of pure DESs were fitted to the Arrhenius equation, and the conductivity values of DESs diluted with 60% and 80% (v/v) water were similar and ranged between 2.13 and 2.20 mS/cm, with increased temperatures. The correlation between pH and surface tension of the three DESs with varying water content and temperature were consistent with the cubic model and viscosity were fitted to the Arrhenius equation. DES with varying water content and reaction temperature had effect on esterification conversion rate of lipase N435, and were fitted to the cubic model. Spearman correlation analysis found a correlation between viscosity and surface tension and conversion rates. The catalytic activity and viscosity, and surface tension in ChCl: urea system was well fitted (R2>0.98). The fitting effect of catalytic activity and viscosity in ChCl: glycerol system, and the fitting effect of catalytic activity and surface tension in ChCl: ethylene glycol system were well (R2>0.98). Catalytic activity and pH in three DESs system were not well fitted (R2<0.78). The results of the study revealed that the use of equations and models to correlate DESs properties with catalyzed synthesis activity was effective and reliable.