Spatially confined lignin nanospheres for biocatalytic ester synthesis in aqueous media

Abstract

Dehydration reactions proceed readily in water-filled biological cells. Development of biocatalysts that mimic such compartmentalized reactions has been cumbersome due to the lack of low-cost nanomaterials and associated technologies. Here we show that cationic lignin nanospheres function as activating anchors for hydrolases, and enable aqueous ester synthesis by forming spatially confined biocatalysts upon self-assembly and drying-driven aggregation in calcium alginate hydrogel. Spatially confined microbial cutinase and lipase retain 97% and 70% of their respective synthetic activities when the volume ratio of water to hexane increases from 1:1 to 9:1 in the reaction medium. The activity retention of industrially most frequently used acrylic resin-immobilized Candida antarctica lipase B is only 51% under similar test conditions. Overall, our findings enable fabrication of robust renewable biocatalysts for aqueous ester synthesis, and provide insight into the compartmentalization of diverse heterogeneous catalysts.

Lignin for Nano‐ and Microscaled Carrier Systems: Applications, Trends, and Challenges

“…Typical controlled release materials are composed of an enzyme‐sensitive substrate linked to another component that leads to changes in macroscopic conformation . Many of the systems developed thus far involve polymer hydrogels, including nanoparticle–polymer hydrogels, which can also be formed from lignin …”

“…Compared to the hydrolytic activity of beads containing only cellulose, the supplementation of KL into the beads increased lipase activity by a factor of 2.6. A higher activity increase by a factor of 3.2 was reported when using lipase from Mucor javanicus , which was first adsorbed on cationic lignin nanospheres and subsequently entrapped in calcium alginate beads at an EE of 96 % . The same authors showed that, in addition to lipases, immobilized cutinase from Humicola insolens catalyzed the synthesis of butyl butyrate in a biphasic solvent mixture (water/hexane ratio 9:1 v / v ).…”

“…Activation of lipases occurs because of the amphiphilic properties of lignins, which are similar to those of synthetic surfactants . Lipase from Aspergillus niger was adsorbed on a composite material consisting of chitin and oxidized KL .…”

“…adsorbed water‐soluble cationized SKL on colloidal lignin particles, achieving a pH‐dependent cationic net charge . Such cationic LNPs were used for emulsion stabilization and enzyme immobilization, but their cytocompatibility has not been assessed. Cationic polymers carrying quaternary amine headgroups are well known for their antimicrobial properties, but cationic lignin particles have not been systematically studied for their possible cytoxicity for mammalian cells.…”

A Middle-Aged Enzyme Still in Its Prime: Recent Advances in the Field of Cutinases

“…T. fusca cutinases have also been covalently immobilized on glutaraldehyde-activated chitosan beads, exhibiting increased thermostability at 55 • C [87]. Cationic lignin nanospheres have been used for the adsorption of H. insolens cutinase (HiC), and they were further entrapped in sodium alginate beads [88]. The resulting catalyst could be used a few times for the synthesis of butyl butyrate, and its t 1/2 under the specific reaction conditions was higher compared to the literature.…”