polymers Review Polymers as Encapsulating Agents and Delivery Vehicles of Enzymes Adejanildo da S. Pereira 1 , Camila P. L. Souza 1 , Lidiane Moraes 1 , Gizele C. Fontes-Sant’Ana 2 and Priscilla F. F. Amaral 1, *   Citation: da S. Pereira, A.; Souza, C.P.L.; Moraes, L.; Fontes-Sant’Ana, G.C.; Amaral, P.F.F. Polymers as Encapsulating Agents and Delivery Vehicles of Enzymes. Polymers 2021, 13, 4061. https://doi.org/10.3390/ polym13234061 Academic Editor: Dimitrios Bikiaris Received: 29 October 2021 Accepted: 13 November 2021 Published: 23 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Escola de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-909, Brazil; adejanildosp@gmail.com (A.d.S.P.); camila_lins@hotmail.com.br (C.P.L.S.); lidiane@eq.ufrj.br (L.M.) 2 Biochemical Processes Technology Department, Chemistry Institute, Universidade do Estado do Rio de Janeiro, Rio de Janeiro 20550-013, Brazil; gizele.santana@uerj.br * Correspondence: pamaral@eq.ufrj.br; Tel.: +55-21-3938-7623 Abstract: Enzymes are versatile biomolecules with broad applications. Since they are biological molecules, they can be easily destabilized when placed in adverse environmental conditions, such as variations in temperature, pH, or ionic strength. In this sense, the use of protective structures, as polymeric capsules, has been an excellent approach to maintain the catalytic stability of enzymes during their application. Thus, in this review, we report the use of polymeric materials as enzyme encapsulation agents, recent technological developments related to this subject, and characterization methodologies and possible applications of the formed bioactive structures. Our search detected that the most explored methods for enzyme encapsulation are ionotropic gelation, spray drying, freeze- drying, nanoprecipitation, and electrospinning. α-chymotrypsin, lysozyme, and β-galactosidase were the most used enzymes in encapsulations, with chitosan and sodium alginate being the main polymers. Furthermore, most studies reported high encapsulation efficiency, enzyme activity main- tenance, and stability improvement at pH, temperature, and storage. Therefore, the information presented here shows a direction for the development of encapsulation systems capable of stabilizing different enzymes and obtaining better performance during application. Keywords: polymers; encapsulation; enzymes; chitosan; sodium alginate 1. Introduction Enzymes are valuable molecules for several reasons, including mild reaction condi- tions, biodegradability, selectivity, high yields, and renewability. In this sense, industries are increasingly demanding their use in quite a few products and processes, mainly in the textile, detergent, starch, pharmaceutical, and fuel sectors [1]. The use of agro-industrial wastes [2,3], media optimization [4], and many modern techniques, such as protein engineering [5] and directed evolution [6], has managed to reduce enzyme production costs and provide many interesting new applications. Even so, the immobilization of these biocatalysts is essential for industrial use because of operational stability and reusability [7]. Besides, immobilization is also a crucial technique for the controlled release of these catalytic proteins at specific locations (target site), at a specific rate, or in response to environmental triggers, such as pH, ionic strength, temperature, or enzymatic activity [8]. These features are important for pharmaceutical applications and can improve the technical–functional performance of these molecules [9]. Numerous immobilization techniques have been studied and are still under investiga- tion to obtain robust high activity biocatalysts, and they are divided into three categories: adsorption on a carrier (support), encapsulation in a carrier (entrapment), and crosslinking (carrier-free) [10]. Regardless of the immobilization strategy, polymers certainly play a crucial role in this process: the use of synthetic, natural, inorganic, and smart polymers has been reported so far [10]. Polymers 2021, 13, 4061. https://doi.org/10.3390/polym13234061 https://www.mdpi.com/journal/polymers