Bioengineering 2021, 8, 154. https://doi.org/10.3390/bioengineering8110154 www.mdpi.com/journal/bioengineering Systematic Review Streptomyces as Potential Synthetic Polymer Degraders: A Systematic Review Maria Fernanda Rodríguez-Fonseca 1,2 , Jeysson Sánchez-Suárez 2 , Manuel Fernando Valero 3 , Sonia Ruiz-Balaguera 4 and Luis Eduardo Díaz 2, * 1 Master in Process Design and Management, School of Engineering, Universidad de La Sabana, Chía 250001, Colombia; mariarofo@unisabana.edu.co 2 Bioprospecting Research Group, School of Engineering, Universidad de La Sabana, Chía 250001, Colombia; jeyssonsasu@unisabana.edu.co 3 Energy, Materials and Environment Group, School of Engineering, Universidad de La Sabana, Chía 250001, Colombia; manuel.valero@unisabana.edu.co 4 Conservation, Bioprospecting and Sustainable Development Group, Environmental Engineering Program, Universidad Nacional Abierta y a Distancia (UNAD), Bogotá 110911, Colombia; sonia.ruiz@unad.edu.co * Correspondence: luis.diaz1@unisabana.edu.co; Tel.: +57-861-5555 (ext. 25208) Abstract: The inherent resistance of synthetic plastics to degradation has led to an increasing chal- lenge of waste accumulation problem and created a pollution issue that can only be addressed with novel complementary methods such as biodegradation. Since biocontrol is a promising eco-friendly option to address this challenge, the identification of suitable biological agents is a crucial require- ment. Among the existing options, organisms of the Streptomyces genus have been reported to bio- degrade several complex polymeric macromolecules such as chitin, lignin, and cellulose. Therefore, this systematic review aimed to evaluate the potential of Streptomyces strains for the biodegradation of synthetic plastics. The results showed that although Streptomyces strains are widely distributed in different ecosystems in nature, few studies have explored their capacity as degraders of synthetic polymers. Moreover, most of the research in this field has focused on Streptomyces strains with promising biotransforming potential against polyethylene-like polymers. Our findings suggest that this field of study is still in the early stages of development. Moreover, considering the diverse eco- logical niches associated with Streptomyces, these actinobacteria could serve as complementary agents for plastic waste management and thereby enhance carbon cycle dynamics. Keywords: biodegradation; Streptomyces; polyethylene; polypropylene; plastics; commodity plastics 1. Introduction Natural and synthetic plastics have replaced numerous materials across industries due to their versatility and overall resistance [1]. These plastics have a desirable strength coupled with outstanding flexibility [1,2]. Both natural and synthetic plastics show high resistance against microbial attacks, but synthetic plastics show better performance over long-term exposure [3], and this higher microbial resistance makes them preferred mate- rials in different industries. Considering the growing importance of synthetic plastics in our daily lives, their pro- duction has risen in the past decade, reaching over 348 million tons worldwide in 2017 [3] and projected to reach 500 million tons by the end of 2020 [4]. From this overall production, five plastics, polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvi- nyl chloride (PVC), low-density polyethylene (LDPE), and polypropylene (PP) [5], stand out for their massive scales of production and consumption. However, this increase in pro- duction and demand has also led to a rise in waste accumulation, since less than 8 million Citation: Rodríguez-Fonseca, M.F.; Sánchez-Suárez, J.; Valero, M.F.; Ruíz-Balaguera, S.; Díaz, L.E. Streptomyces as Potential Synthetic Polymer Degraders: A Systematic Review. Bioengineering 2021, 8, 154. https://doi.org/10.3390/ bioengineering8110154 Academic Editor: Bruna Matturro and Marco Zeppilli Received: 24 September 2021 Accepted: 20 October 2021 Published: 23 October 2021 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2021 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).