Enhancing lipases reactivity in benzylic acetates hydrolysis: impact of kosmotropic salts under non-conventional conditions

Abstract

The effect of four kosmotropic salts additives, namely Na₂CO₃, Na₂SO₄, Na₂HPO₄, and NaCl, on the reactivity and selectivity of immobilized Candida antarctica lipase B (CAL-B) and a free lipase of Pseudomonas cepacia (PCL) during the hydrolysis of rac-4-(1-methoxyphenyl) ethyl and rac − 1-phenyl ethyl acetates (1a-2a) was investigated in this study. The study was carried out in two different mediums: non-aqueous conditions and in low water content media. The impact of the anionic counter-ions was examined in four solvents: nonpolar, semipolar, protic, and aprotic, with and without the aforementioned salts. In non-aqueous media, the addition of Na₂CO₃ significantly enhanced CAL-B hydrolysis rates, resulting in a conversion of 50% for 1a and 44% for 2a, with high enantioselectivities (E > 200). These effects were independent of the solvent hydrophobicity. In contrast, PCL required the presence of external water for effective hydrolysis of both acetates. The addition of salt additives had an adverse impact on PCL activity during the hydrolysis of 1a in hexane, toluene, and TBME solvents. However, when 2M2B was used, the inclusion of salt additives had a notable positive effect on the conversion rates, except for NaCl, which resulted in a lower conversion rate with a value of 15.5%. The presence of Na₂CO₃ improved the conversion rate during the hydrolysis of 2a in both hexane and TBME. Na₂HPO₄ further enhanced the conversion rate, reaching 44% in TBME. However, in 2M2B solvent, the addition of Na₂HPO₄ significantly reduced the enantioselectivity.

Graphical Abstract

Keywords:

• Kosmotropic salts additives
• Enzymatic kinetic resolution
• Hydrolysis
• CAL-B
• PCL
• Hydrophobicity
• non-conventional media

Acknowledgements

The authors gratefully acknowledge the financial support provided by the Algerian Ministry of Higher Education and Scientific Research (MESRS, FNR 2000) for this work. The authors would also like to express their gratitude to Achwaq ZADEM and Rima AZIAR, Master’s students, for their technical assistance during the preliminary study.

Author contributions

All the experiments and analyses reported in this study were conducted by Nabila BRAIA and Mounia MERABET-KHELASSI. The study was conceived, designed, and supervised by Mounia MERABET-KHELASSI. Mounia MERABET-KHELASSI and Nabila Braia contributed to writing the draft version of the manuscript. Farida LARIT reviewed and corrected the final version of the manuscript. Nabila BRAIA acknowledges Farida LARIT for their valuable discussions. All authors have read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).