Genomic Science Program
U.S. Department of Energy | Office of Science | Biological and Environmental Research Program

Developing Chassis for Low Density Polyethylene Upcycling from Microbes Native to the Gut Microbiome of Yellow Mealworms

Authors:

Jenna Ott1*, Ross Klauer1, Alex Hansen1, Lummy Maria Oliveira Monteiro1, Zoé O. G. Schyns1 Bill Alexander2, Michael Melesse Vergara2, Runyu Zhao3, Yinjie Tang3, LaShanda T. J. Korley1, Adam Guss2, Carrie Eckert2, Kevin Solomon1, Mark Blenner1

Institutions:

1Chemical and Biomolecular Engineering, University of Delaware; 2Oak Ridge National Laboratory; 3Washington University in St. Louis

Goals

This project aims to enable the efficient deconstruction of polyolefins and upcycling to itaconic acid, through novel genomic insights into nutrient enhanced polyolefin degradation by the yellow mealworm gut microbiome and genetic tool development for gut microbiome isolates and engineered microbial communities.

Abstract

Annually more than 200 million tons of plastic waste in the form of polypropene, high density polyethylene, and low density polyethylene (LDPE) are generated and accumulate in the environment. No robust system exists to capture this carbon; however, in prior work, researchers identified myriad upregulated non-model species in plastic-fed mealworm guts. Moreover, team members previously showed that gut isolates from these genera grow on LDPE as their primary carbon source and chemically modify LDPE films upon inoculation. These taxa have been identified as upcycling chassis for development due to their prevalence in plastic enriched microbial communities.

As a prerequisite for targeted genetic engineering, the research team collected genome and methylome sequence data of gut eight isolates that can grow on LDPE as their primary carbon source. The research group successfully identified methylation motifs in each of the eight isolates and have located and annotated methyltransferases in the genome of each strain. Escherichia coli strains capable of producing plasmids with these tailored methylation patterns greatly facilitates transformation and genetic engineering for future community engineering efforts.

To further understand the role of microbial isolates in plastics deconstruction processes and holistic gut community degradation processes, a collection of metaomics datasets are being developed. Synergizing findings from transcriptomes, proteomes, and metabolomes, as well as hypothetical pathways for LDPE deconstruction, are iteratively being built. This community-wide systems biology approach allows for a complete picture of degradation processes by highlighting genes, proteins, and metabolites that coincide as upregulated in plastics-enriched gut communities.

Existing microbial isolates and those identified through metaomics approaches will ultimately be constructed into synthetic plastic-degrading communities capable of plastics waste valorization. To better recapitulate mealworm gut community behavior, researchers are investigating the ability of minimal synthetic microbial communities to deconstruct LDPE. Researchers identified co-cultures that are metabolically active in media with LDPE as the sole carbon source. Preliminary data suggest that certain microbial isolates have enhanced plastic degradation potential in co-culture conditions. The group is further investigating co-culture behaviors using confocal microscopy to image microbial spatial variances and plastic particle surface colonization. Identifying essential features in minimal co-cultures will inform the design of more complex synthetic communities capable of enhanced plastic degradation.

Beyond microbial work, researchers must consider polymer characteristics to develop improved deconstruction systems. Post-consumer waste plastics contain additive packages to improve processability, antioxidation, and flame retardancy. Given additive variability among polymer grades, researchers developed a standardized plastics preparation procedure wherein additives are stripped from polymers, leaving only the base plastic for deconstruction studies. The use of stripped plastics facilitates a more accurate comparison of deconstruction rates across plastic materials from various sources. Additionally, researchers’ current work leverages successive self-seeding and annealing (SSA), differential scanning calorimetry (DSC), and thermal fractionation techniques to assess polymer architecture (e.g., branching densities) pre- and post-deconstruction. Preliminary data indicate that deconstruction predominantly occurs at low branching densities, indicating that high branching density plastics such as LDPE are less bioavailable than low branch-density plastics. Future efforts will concentrate on validating chain architecture hypotheses and on elucidating the mechanism of polyethylene deconstruction from a branching perspective.

Funding Information

This material is based upon work supported by the U.S. DOE, Office of Science, BER program, GSP under Award Number DE-SC0023085. A portion of this research will be performed under the Facilities Integrating Collaborations for User Science (FICUS) initiative and use resources at the DOE Joint Genome Institute and the Environmental Molecular Sciences Laboratory, which are DOE Office of Science User Facilities. Both facilities are sponsored by the BER program and operated under Contract Nos. DE-AC02-05CH11231 (JGI) and DE- AC05-76RL01830 (EMSL).