# Enzymatic Hydrolysis of Triacetin and L-Lactide in Emulsified Microparticles Within a Cellulose Hydrogel Dispersion

## TL;DR

This study examines how cellulose hydrogel stabilizes emulsions and affects enzyme activity during the breakdown of triacetin and lactide.

## Contribution

The study reveals a synergistic effect of cellulose hydrogel on the interfacial activation of Candida rugosa lipase during enzymatic hydrolysis.

## Key findings

- Emulsions prepared with a two-step process had smaller triacetin droplets and a more uniform cellulose hydrogel dispersion.
- L-lactide inhibited enzymatic hydrolysis of triacetin, but this was mitigated by cellulose hydrogel for Candida rugosa lipase.
- Cellulose hydrogel stabilization enhanced the interfacial activation of Candida rugosa lipase but not Burkholderia cepacia lipase.

## Abstract

Triacetin (TA) is a solvent commonly used in pharmaceutical and food applications, and as a plasticizer in bioplastics such as poly(lactic acid) (PLA) and cellulose acetate (CA). L-lactide is the monomer used in the ring-opening polymerization of PLA. The structure of TA emulsions stabilized by a cellulose hydrogel (CH) was imaged in this study. The emulsions were prepared by mechanical homogenization or a two-step process with subsequent high-pressure homogenization (HPH). The two-step process yielded smaller TA droplets and a more homogeneous CH dispersion. The images demonstrate that emulsion stabilization is due to CH particles adsorbed at the TA–water interface. The ester hydrolysis of TA and a lactide/TA solution by two industrially important lipases, from Candida rugosa (CRL) and Burkholderia cepacia (BCL), was investigated, assessing the effect of CH as an emulsion stabilizer. Mechanically homogenized TA emulsions were effectively hydrolyzed. Lactide was found to inhibit the enzymatic hydrolysis of TA. This inhibition was mitigated by CH for CRL-catalyzed hydrolysis but not for BCL catalysis. These results indicate a synergistic effect of CH stabilization on the interfacial activation of CRL. Thise effect may also be relevant for the biodegradation of bio-derived plastics and their fibrous cellulose composites.