Many abiotic reactions accessible through synthetic organic chemistry are not found in nature. Incorporating such reactions into living systems offers a promising solution for the sustainable synthesis of various commercially available chemicals from renewable and waste-derived resources. The development of biocompatible reactions, non-enzymatic chemical transformations that function within living cells, has emerged as a powerful tool that increases the biochemical capacities of living organisms.
With the latest advancements in this area, it isn’t easy to incorporate non-native chemistry into cellular metabolism. The production of small molecules using entirely non-enzymatic pathways within living cells is still rare. In this study, researchers report the successful implementation of a biocompatible Lossen rearrangement within Escherichia coli (E. coli), demonstrating its compatibility with cellular metabolism. It is used in the sustainable production of small molecules from resources derived from plastic waste, such as polyethylene terephthalate (PET).
Artificial metalloenzymes were used in metabolically modified microbial cells to produce both substrates and apoenzymes in the cell core of biosynthesis. The non-enzymatic rearrangement of activated carboxylate substrates and their integration into native and engineered metabolic pathways exemplify a new mode of biocompatible synthetic chemistry in living systems. In Salmonella typhimurium TA98, Lossen-type rearrangements are intermediates that exhibit hydroxamic acid toxicity, as demonstrated in vitro as unproductive substrates when tested with enzymes such as chymotrypsin.
In this study, exogenous alkenes and polyethylene terephthalate (PET)-derived para-aminobenzoate (PABA) underwent conditional biotransformation, suggesting metabolic collaboration with the Lossen rearrangement and revealing the potential for cooperative interaction between chemical and cellular processes. Humans and other auxotrophic organisms should extract these vital nutrients from their immediate surroundings or from nearby microorganisms. According to some published reports, metal complexes support Lossen or Curtius rearrangements and similar reactions under mild or wet conditions.
The Lossen rearrangement was mediated by phosphate after each component of the M9 minimal medium was gradually removed, and the results were compared with PABA production in phosphate-buffered saline (PBS). OD600 and colony-forming units (CFU) per millilitre in the 10 to 1,000 µM range showed that all substrates were biocompatible with E. coli growth. Approximately 80% of the 56 million tons of PET produced annually is used for single-use purposes, resulting in the annual generation of 24 million tons of PET waste that is either burned or disposed of in landfills. The World Health Organization (WHO) recommends paracetamol as the first-line treatment for fever and pain. It is made from phenol, including nitration, reduction, and N-acetylation processes with acetic anhydride to form an oral drug.
The reaction was continued by the deprotonation of the N–H group, followed by a 1,2-aryl migration, as demonstrated by control studies involving N-methylated or O-acylated analogues. Researchers found that E. coli cultures rescued by substrate one performed whole-cell biocatalytic reductions, efficiently converting dimethyl maleate and keto-acrylates into their corresponding products. Future research will utilize synthetic biology techniques to improve the utilization of the de novo route, thereby enhancing flux into paracetamol biosynthesis. This work showcases the successful integration of a fully biocompatible Lossen rearrangement into microbial metabolism, enabling the production of amine-containing metabolites and pharmaceutical precursors from plastic waste.
In conclusion, this study advances chemical biotechnology by bridging synthetic organic chemistry and microbial metabolism, providing an innovative and sustainable route for generating high-value compounds and reducing environmental plastic waste.
Reference: Johnson NW, Valenzuela-Ortega M, Thorpe TW, et al. A biocompatible Lossen rearrangement in Escherichia coli. Nat Chem. 2025. doi:10.1038/s41557-025-01845-5
