Developing a High-Throughput Fluorescence Screen to Detect LDPE Biological Deconstruction

• Rachel Holloway, Chemical Engineering, University of Delaware

• Kevin Solomon, Chemical and Biomolecular Engineering, University of Delaware
• Mark Blenner, Chemical and Biomolecular Engineering, University of Delaware

Traditional plastic deconstruction methods include chemical and mechanical recycling. Alternatively, biological degradation, an approach where microorganisms are used to break down plastic, is a more energy efficient process with fewer side/by-products. Low-density polyethylene (LDPE), the most abundant form of plastic waste, lacks characterized biocatalysts necessary to make it a candidate for bio-deconstruction. One of the biggest hurdles to discovering PE-active biocatalysts is a lack of high-throughput assays of bona fide deconstruction. To address this issue, we sought to develop a high-throughput fluorescence assay to quantify LDPE degradation. Rhodamine 6G (R6G), a commercially available fluorophore, is incorporated into LDPE to create a fluorophore-doped polymer. Yellow mealworms have been shown to degrade LDPE, so we aim to determine if R6G-LDPE can be degraded in the same manner. In this case, fluorescence leaching into the mealworm gut can potentially correlate with plastic deconstruction. The mealworms were fed bran with a supplemental R6G-LDPE diet. Periodically, mealworm guts were extracted and a plate reader was used to measure fluorescence. Gel permeation chromatography (GPC) was used at the end of the trial to measure deconstruction. However, we determined that R6G-LDPE was not deconstructed like LDPE was, indicating that part of the synthesis pathway inhibits bio-deconstruction. Two hypotheses for the lack of deconstruction include i) differences in material properties observed after melt blending or ii) R6G itself is the inhibiting factor. To address these hypotheses, additional testing includes incorporating R6G into bran as well as using a new synthesis method for R6G-LDPE that does not include melt blending, which caused preliminary polymer degradation. The development of high-throughput assays will aid in overcoming the hurdles of bio-catalyst identification, allowing for more efficient strides towards bio-deconstruction.