Polyethylene glycols (PEGs) are a major class of synthetic water-soluble polymers (WSPs) with an annual global production volume of approximately 600 kilotons. In home and personal care products, PEGs act as emulsifiers and moisture carriers. In these applications, PEGs are typically diluted in water and are discarded in household wastewater streams. In agricultural formulations, PEGs emulsify and stabilize pesticides and fertilizers, thereby ensuring their efficient application. A common feature of these applications is that PEGs are subject to dissipative release, either to wastewater treatment plants or agricultural soils. The latter may also receive indirect inputs when fertilized with PEG-containing sludge. Despite these release pathways into natural and engineered systems, the environmental chemistry and fate of PEGs -as well as of WSPs in general -remains poorly studied and understood. Besides transport and mobility considerations, transformation processes, such as extracellular chain-scission reactions, are of particular relevance. Biodegradation, a process in which microorganisms take up and metabolically convert PEGs into CO2 and microbial biomass, can be considered the ultimate transformation endpoint. Previous studies have proposed that this microbial utilization of PEGs occurs through end-group specific (i.e., exolytic) oxidation reactions catalyzed by three intracellular enzymes: an alcohol dehydrogenase, which converts the terminal alcohols into aldehydes; an aldehyde dehydrogenase, which oxidizes the aldehydes to carboxylic acids; and, finally, an ether bond-cleaving enzyme (e.g., a-hydroxy acid dehydrogenase), which acts on the carboxylic end groups releasing glyoxylates, thereby shortening the PEG chain by one unit. The glyoxylates are then further metabolized to CO2.