The biodegradation of polyethylene glycols by sewage bacteria

Abstract

Several strains of bacteria able to degrade polyethylene glycols (PEG) have been isolated from sewage effluent and the effect of molecular weight on biodegradability determined. Acinetobacter SC 25, isolated using PEG 400 as enrichment substrate, could grow on and degrade ethylene glycol, diethylene glycol, triethylene glycol, PEG 200 and 400 and very slowly utilize PEG 600, 800 and 1000 as sole carbon source in a mineral salts medium. In the presence of artificial sewage the rate and extent of biodegradation of the higher molecular weight PEGs was increased and even PEG 1500 was partly degraded. Pseudomonas KW 8 could also biodegrade ethylene glycol and all PEGs up to PEG 400 and slowly attack PEG 600 but the longer PEGs were not degraded. Under conditions of slow growth and biodegradation both bacteria produced carboxylated intermediates containing the R—OCH 2COOH group but these intermediates were further degraded under suitable conditions. Flavobacterium BT 1, isolated using PEG 1500 as enrichment substrate, could attack PEG 200, 400, 600, 800, 1000 and 1500 but not ethylene glycol, diethylene glycol or triethylene glycol. None of the isolated bacteria could grow on PEG 4000 or the polypropylene glycols. The results confirm that PEGs are biodegradable and suggest that biodegradation might be more rapid during sewage treatment, or in biodegradability tests where other nutrients are present, than in die-away tests where the PEG is the sole carbon source.