Characterisation of three aerobic bacteria isolated from NPEO-contaminated sludges

In this work, three aerobic bacteria were isolated from activated sludges contaminated by nonylphenol polyethoxylates and characterised. Two of them, namely BCaL1 and BCaL2 were Gram negative rods, the third, VA160, was a Gram positive bacterium with a rhizoid colony shape. Analysis of the 16S ribosomal DNAs showed that the three strains could be assigned to Acinetobacter (BCaL1) Stenotrophomonas (BCaL2) and Bacillus (VA160) genera. Their degradation ability towards commercial mixtures of nonylphenol ethoxylates, in particular towards a mixture having an average ethoxylation degree of five, was investigated in aerobic batch culture conditions. Results showed that the Acinetobacter and Stenotrophomonas strains were both able to degrade some components of the surfactant mixture. On the contrary Bacillus VA160 did not exhibit any detectable biodegradation activity, but, when co-cultured with the other two strains, it was capable of positively affecting their degradation ability.