Bacterial attack of non-ionic aromatic surfactants: Comparison of degradative capabilities of new isolates from nonylphenol polyethoxylate polluted wastewaters

Nonylphenol polyethoxylates (NPEOs) are largely used in many different industrial applications. In 1987 estimated production of NPEOs in Europe was 150,000 tons, with 25,000 tons only produced in Italy (1). They represent a group of compounds which are of environmental concern because of their toxicity to biological systems. Furthermore, NPEOs and their intermediates tend to accumulate in sewage sludge during wastewater depuration or possibly in sediments once heated waters are discharged into rivers and sea. Primary degradation of NPEOs, that also means the loss of surfactant properties, easily occurs in aerobic conditions as a consequence of the progressive loss of ethylene oxide units. On the other hand, complete mineralization appears to proceed very slowly. Anyway scarce information is available about microorganisms which possibly carry out biodegradation of these compounds. The present paper reports results concerning the isolation and characterization of three different Gram negative bacteria from nonylphenol polyethoxylate contaminated sludge, that can individually attack NPEOs in axenic cultures effecting primary degradation.