Efficient biodegradation of high-molecular-weight polyethylene glycols by pure cultures of Pseudomonas stutzeri

Biodegradation of polyethylene glycols (PEGs) of up to 13,000 to 14,000 molecular weight has been shown to be performed by a river water bacterial isolate (strain JA1001) identified as Pseudomonas stutzeri. A pure culture of strain JA1001 grew on PEG 1000 or PEG 10000 at 0.2% (wt/vol) as a sole source of carbon and energy with a doubling time of 135 or 150 min, respectively. Cultures metabolized 2 g of polymer per liter in less than 24 h and 10 g/liter in less than 72 h. The limit of 13,500 molecular weight in the size of the PEG sustaining growth and the presence of a PEG-oxidative activity in the periplasmic space indicated that PEGs cross the outer membrane and are subsequently metabolized in the periplasm. PEG oxidation was found to be catalyzed by PEG dehydrogenase, an enzyme that has been shown to be a single polypeptide. Characterization of PEG dehydrogenase revealed glyoxylic acid as the product of the PEG-oxidative cleavage. Glyoxylate supported growth by entering the cell and introducing its carbons in the general metabolism via the dicarboxylic acid cycle, as indicated by the ability of strain JA1001 to grow on this compound and the presence of malate synthase, the first enzyme in the pathway, in extracts of PEG-grown cells.