Deep Eutectic Solvents as Suitable Solvents for Lipase-Catalyzed Transesterification Reactions

Area of Science:

• Green Chemistry
• Biocatalysis
• Sustainable Solvents

Background:

• Deep eutectic solvents (DES) offer environmentally benign alternatives to conventional organic solvents.
• Lipases are versatile enzymes for ester synthesis, but their activity can be solvent-dependent.
• Sugar fatty acid esters (SFAE) have diverse applications, necessitating efficient and sustainable synthesis methods.

Purpose of the Study:

• To investigate three distinct deep eutectic solvents (DES) as reaction media for enzymatic synthesis of glucose laurate and glucose acetate.
• To evaluate the catalytic efficiency of three lipases (Aspergillus oryzae, Candida rugosa, porcine pancreas) in these DES for SFAE production.
• To identify optimal DES-lipase combinations for high-yield synthesis of specific SFAE under mild conditions.

Main Methods:

• Synthesis of glucose laurate and glucose acetate using enzymatic transesterification.
• Employing three different deep eutectic solvents: choline chloride/urea (DES1), choline chloride/glycerol (DES2), and tetrabutylammonium bromide/imidazole (DES3).
• Utilizing lipases from Aspergillus oryzae (LAO), Candida rugosa (LCR), and porcine pancreas (LPP) as biocatalysts.
• Assessing lipase hydrolytic activity in DES to confirm enzyme stability.

Main Results:

• Lipase stability was confirmed in all tested DES.
• Optimal glucose laurate synthesis (>60% conversion) achieved with LAO or LCR in DES3.
• Porcine pancreas lipase in DES2 yielded 98% glucose laurate production within 24 hours.
• Glucose acetate synthesis exceeded 80% with LCR and LPP in DES1 after 48 hours.
• LAO showed lower activity for glucose acetate synthesis, reaching ~40% in DES3.

Conclusions:

• Deep eutectic solvents are effective and stable media for lipase-catalyzed SFAE synthesis.
• Specific DES-lipase pairings are crucial for efficient production of different SFAE.
• This approach offers a greener and sustainable alternative for producing valuable sugar fatty acid esters.