Modulating the hydrophobicity of cellulose by lipase-catalyzed transesterification

Area of Science:

• Biocatalysis and Green Chemistry
• Materials Science and Engineering
• Polymer Chemistry

Background:

• Conventional production of hydrophobic cellulosic fibers involves harsh chemicals and toxic by-products.
• Biocatalysis offers a milder, environmentally friendly alternative for modifying cellulose.
• Lipase-catalyzed grafting of hydrophobic moieties onto nanocellulose has been previously demonstrated.

Purpose of the Study:

• To investigate the lipase-catalyzed esterification of native cellulose fibers, glucanase-pretreated fibers, and cellulose nanocrystals (CNC) under solvent-free conditions.
• To evaluate the degree of ester formation and substitution.
• To assess the functional properties, including hydrophobicity and lipophilicity, of the modified cellulose materials.

Main Methods:

• Lipase-catalyzed esterification of cellulose with methyl myristate at 50°C in solvent-free conditions.
• Pretreatment of cellulose fibers with 1,4-β-glucanases.
• Characterization using ATR-FTIR, 13C CP/MAS NMR, and Optical Photothermal Infrared (O-PTIR) spectroscopy.
• Measurement of water contact angle and evaluation of paper composites.

Main Results:

• Successful esterification of cellulose fibers and CNCs confirmed by spectroscopic methods (ATR-FTIR, 13C CP/MAS NMR) with a degree of substitution up to 0.1.
• Glucanase-pretreated cellulose esters exhibited the highest water contact angle (117° ± 9°).
• Esterified cellulose in paper composites showed enhanced hydrophobicity and lipophilicity.
• Reversibility of esterification was demonstrated via lipase treatment in aqueous media.

Conclusions:

• Lipase-catalyzed esterification provides an efficient and green route for producing hydrophobic cellulosic materials.
• Glucanase pretreatment significantly enhances the hydrophobic properties of the esterified cellulose.
• These functionalized cellulose fibers hold promise for sustainable packaging applications.