Agar-based Pickering emulsion: A platform for enzymatic and chemoenzymatic synthesis

Pickering emulsions, with their high specific surface area, serve as promising nanoreactors for highly efficient biocatalysis. These emulsions also provide an effective way to integrate multiple incompatible catalysts, such as enzymatic catalysis and metal catalysis, paving the way for green synthetic chemistry in the future. In this study, we used agar, an accessible and biodegradable material, to produce agar nanoparticles with varying properties by modifying them with phthalic anhydride. The agar nanoparticle-stabilized Pickering emulsion greatly enhanced the lipase-catalyzed esterification reaction, demonstrating 392- and 38-fold improvements compared with monophasic and biphasic catalytic systems, respectively. After 10 reuse cycles of the Pickering emulsion, the product yield remained 86.5 %, with the relative enzyme activity being 86.6 %. Furthermore, we successfully integrated lipase-catalyzed esterification and Pd-catalyzed C C coupling reactions within the Pickering emulsion. By increasing the interfacial reaction area and reducing the mass transfer distance, this system improved the efficiency of the chemoenzymatic cascade reaction. The agar-based Pickering emulsion provides a promising platform for efficient and sustainable green synthesis, utilizing enzyme catalysts or chemical-biological hybrid catalysts.