Two-step conversion of polyethylene into recombinant proteins using a microbial platform

• Published in: Microbial cell factories Vol. 22; no. 1; pp. 1 - 214
• Main Authors: Connor, Alexander, Lamb, Jessica V, Delferro, Massimiliano, Koffas, Mattheos, Zha, R. Helen
• Format: Journal Article
• Language: English
• Published: London BioMed Central Ltd 17.10.2023; BioMed Central; Springer Science + Business Media; BMC
• Subjects: Alkanes; Ammonium chloride; Bacteria; Biological products; Biomaterials; Biomedical materials; Biopolymers; Carbon; Carbon sources; Cell growth; Depolymerization; Fluorescence; Green fluorescent protein; Hexadecane; Hydrocarbons; Microbial upcycling; Microorganisms; Nitrogen; Plastic debris; Plastic scrap; Plastic waste; Plastics; Polyethylene; Polyethylenes; Polyhydroxyalkanoates; Proteins; Pseudomonas aeruginosa; Raw materials; Recombinant proteins; Recombinant silk; Recycling; Recycling (Waste, etc.); Scientific equipment and supplies industry; Silk; Substrates; Sustainability; Sustainable development; Sustainable materials; Synthetic biology; United States; Waste management; Waste streams; United States
• ISSN: 1475-2859; 1475-2859
• DOI: 10.1186/s12934-023-02220-0

The increasing prevalence of plastic waste combined with the inefficiencies of mechanical recycling has inspired interest in processes that can convert these waste streams into value-added biomaterials. To date, the microbial conversion of plastic substrates into biomaterials has been predominantly limited to polyhydroxyalkanoates production. Expanding the capabilities of these microbial conversion platforms to include a greater diversity of products generated from plastic waste streams can serve to promote the adoption of these technologies at a larger scale and encourage a more sustainable materials economy. Herein, we report the development of a new strain of Pseudomonas bacteria capable of converting depolymerized polyethylene into high value bespoke recombinant protein products. Using hexadecane, a proxy for depolymerized polyethylene, as a sole carbon nutrient source, we optimized media compositions that facilitate robust biomass growth above 1 x 10.sup.9 cfu/ml, with results suggesting the benefits of lower hydrocarbon concentrations and the use of NH.sub.4Cl as a nitrogen source. We genomically integrated recombinant genes for green fluorescent protein and spider dragline-inspired silk protein, and we showed their expression in Pseudomonas aeruginosa, reaching titers of approximately 10 mg/L when hexadecane was used as the sole carbon source. Lastly, we demonstrated that chemically depolymerized polyethylene, comprised of a mixture of branched and unbranched alkanes, could be converted into silk protein by Pseudomonas aeruginosa at titers of 11.3 [+ or -] 1.1 mg/L. This work demonstrates a microbial platform for the conversion of a both alkanes and plastic-derived substrates to recombinant, protein-based materials. The findings in this work can serve as a basis for future endeavors seeking to upcycle recalcitrant plastic wastes into value-added recombinant proteins.