Recovery of organic acids and alcohols from dilute aqueous streams by enzyme-catalyzed reactive extraction of esters is imparted by the predominant reverse hydrolysis reaction. Immobilization of enzymes in spatially confined environments holds opportunities to overcome this barrier. Our hypothesis was that spherical colloidal lignin particles (CLPs) could be beneficial carriers for hydrolases if confined within a stable polymer matrix. For this, we developed a one-pot immobilization process that included the following three steps: (i) Adsorption of cationic lignin on CLPs to render their surface charge positive and susceptible to binding enzymes with a negative net charge. (ii) Adsorption of hydrolases on cationic c-CLPs, and (iii) Entrapment of the enzyme-c-CLP complexes into a calcium alginate hydrogel matrix. Moisture reduction from the alginate hydrogel led to the assembly c-CLP-anchored enzymes into confined catalytic clusters. Spatially confined microbial cutinase and lipase retained 95% and 70% of their respective synthetic activities when the volume ratio of water to hexane increased 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 was only 51% under similar test conditions. Overall, our findings enable fabrication of robust biocatalysts for aqueous ester synthesis, and provide insight into the compartmentalization of diverse array of biological macromolecules.

Novel applications of lignin: Spatially confined lignin nanospheres for biocatalytic ester synthesis in aqueous media

256th National Meeting (2018)

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