Defined Microbial Mixed Culture for Utilization of Polyurethane Monomers

Abstract

The end-of-life plastic crisis is very prominent in the research area and even in the public realm. Especially, for plastic polymers that are difficult to recycle via traditional routes such as the polyurethanes (PUs), novel routes should be investigated. In 2015, PU contributed about 16 million metric tons of global plastic waste. While polymer degradation via chemical routes such as solvolysis and pyrolysis are feasible, the challenge of PU chemical recycling is in the varying mixture and composition of its monomers. Here, we propose a biotechnological route to utilize PU hydrolysate as a carbon source for a defined microbial mixed culture. The mixed culture consists of dedicated microbes, each trained to utilize a single PU monomer and further engineered to produce valuable products. While three Pseudomonas putida KT2440 derivatives utilized adipic acid, 1,4-butanediol, and ethylene glycol, respectively, a recently described Pseudomonas sp. TDA1 used 2,4-toluenediamine (TDA) as a sole carbon source. However, TDA clearly inhibited mixed substrate utilization by the mixed culture, and it also has a high intrinsic value. Therefore, TDA reactive extraction before PU monomer utilization was established, allowing full utilization of the remaining PU monomers as carbon sources for rhamnolipid production. The results highlight the potential of (bio)­technological plastic upcycling.

Progressing Plastics Circularity: A Review of Mechano-Biocatalytic Approaches for Waste Plastic (Re)valorization

“…Due to the fact that TDA inhibited the growth of other consortium members, TDA had to be extracted for the efficient rhamnolipid production. Even after TDI extraction, rhamnolipid production of the consortium was lower than that of each individual strain on the preferred monomer ( Utomo et al, 2020 ).…”

Investigating Physio-Thermo-Mechanical Properties of Polyurethane and Thermoplastics Nanocomposite in Various Applications

“…The structure and properties of PU parts have been investigated to achieve better biocompatibility and are characterized by surface and bulk morphology [10]. Traditionally, PU items are equipped with many organic solvents and free isocyanate monomers [11]. In the production of PU foams, catalysts are employed in the polyaddition reaction [12].…”

MIXed plastics biodegradation and UPcycling using microbial communities: EU Horizon 2020 project MIX-UP started January 2020

“…The main drawback for using lignocellulose, molasses, sludge or organic wastes as feedstock in pure-culture fermentations is the heterogeneity of the feedstocks, non-aseptic conditions and the high costs for substrate pre-treatments. Although mixed cultures as industrial microbiomes are well established in the fields of biofuels (biogas, bio-hydrogen, butanol-production), biobased chemicals, and biopolymers, the emphasis in industrial biotechnology still lies on pure cultures [ 63 – 66 ]. The specific advantages of mixed-culture fermentation compared with pure culture are (i) the possibility of utilising cheaper or mixed substrates (e.g.…”

“…However, efficient growth could not be achieved on all monomers. Subsequently, via genetic engineering, the P4SB partners could generate recombinant P. putida strains capable of efficient catabolism of ethylene glycol, terephthalic acid, and 1,4-butanediol [ 13 , 14 , 66 , 78 ]. For the valorisation of plastic monomers, besides PHA synthesis, hydroxy alkanoyl oxy-alkanoic acids (HAA) synthesis has been successfully established.…”