Versatile microbial communities rapidly assimilate ammonium hydroxide-treated plastic waste

Abstract

Most plastic waste accumulates in landfills or the environment. Natural microbial metabolisms can degrade plastic polymers. Unfortunately, biodegradation of plastics is slow even under ideal conditions; depolymerization of plastic is the rate limiting step. Rapid chemical depolymerization yields biodegradable plastic monomers, improving biodegradation rates. Here we demonstrate that ammonium hydroxide depolymerizes PET into terephthalic acid and terephthalic acid monoamide which are rapidly metabolized by diverse consortia obtained from compost and sediment. By neutralizing the product with phosphoric acid prior to bioprocessing, the final product contains plastic-derived carbon and biologically accessible nitrogen and phosphorus from the process reactants, removing the need for culture medium. Three microbial consortia were able to degrade chemically deconstructed PET in ultrapure water and scavenged river water without the addition of nutrients, with no statistically significant difference in growth rate compared to communities grown on deconstructed PET in Bushnell Haas minimal culture medium. The consortia were dominated by Rhodococcus spp., Hydrogenophaga spp., and many lower abundance genera. All taxa were related to species known to degrade aromatic compounds. Microbial consortia are known to confer flexibility in processing diverse substrates. To highlight the versatility of these consortia, we also demonstrate that two microbial consortia can grow on similarly deconstructed polyesters, polyamides, and polyurethanes in water instead of medium. Our findings suggest that using microbial communities enable flexible bioprocessing of mixed plastic wastes. We also demonstrate the flexibility of this approach for coupled chemical deconstruction and bioprocessing.

Coexistence of specialist and generalist species within mixed plastic derivative-utilizing microbial communities

“…Much of the previous work using microorganisms for tandem chemical and biological plastic-upcycling has utilized isolates or bioengineered microorganisms to either convert waste PET into virgin materials or value-added compounds [10,18,52]. Other studies have shown the microbial communities are able to metabolize deconstructed plastics treated either with pyrolysis or chemical deconstruction [16,53,54]. Here, we use a microbial community instead of an isolate to demonstrate that a microbial community consists of specialist and generalist species, which allows flexibility to degrade processed mixed plastic waste.…”

“…LS1_Calumet and EB2_Mackinac consortia have been previously described by Schaerer et al [54] and Byrne et al [53]. The LS1_Calumet enrichment was enriched from a compost sample collected from a farm in Calumet, MI (Coordinates 47.211, − 88.553) by adding 1 g of compost per 100 mL of 10 g/L disodium terephthalate in Bushnell Haas medium, incubating at room temperature stirring continuously.…”