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Applied and Environmental Microbiology, October 2007, p. 6214-6223, Vol. 73, No. 19
0099-2240/07/$08.00+0     doi:10.1128/AEM.01230-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Characterization of the Polyurethanolytic Activity of Two Alicycliphilus sp. Strains Able To Degrade Polyurethane and N-Methylpyrrolidone{triangledown}

Alejandro Oceguera-Cervantes,1 Agustín Carrillo-García,1 Néstor López,2 Sandra Bolaños-Nuñez,3 M. Javier Cruz-Gómez,2 Carmen Wacher,3 and Herminia Loza-Tavera1*

Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, 04510 México, D.F. México,1 Departamento de Ingeniería Química, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, 04510 México, D.F. México,2 Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, 04510 México, D.F. México3

Received 1 June 2007/ Accepted 1 August 2007

Two bacterial strains (BQ1 and BQ8) were isolated from decomposed soft foam. These were selected for their capacity to grow in a minimal medium (MM) supplemented with a commercial surface-coating polyurethane (PU) (Hydroform) as the carbon source (MM-PUh). Both bacterial strains were identified as Alicycliphilus sp. by comparative 16S rRNA gene sequence analysis. Growth in MM-PUh showed hyperbolic behavior, with BQ1 producing higher maximum growth (17.8 ± 0.6 mg·ml–1) than BQ8 (14.0 ± 0.6 mg·ml–1) after 100 h of culture. Nuclear magnetic resonance, Fourier transform infrared (IR) spectroscopy, and gas chromatography-mass spectrometry analyses of Hydroform showed that it was a polyester PU type which also contained N-methylpyrrolidone (NMP) as an additive. Alicycliphilus sp. utilizes NMP during the first stage of growth and was able to use it as the sole carbon and nitrogen source, with calculated Ks values of about 8 mg·ml–1. Enzymatic activities related to PU degradation (esterase, protease, and urease activities) were tested by using differential media and activity assays in cell-free supernatants of bacterial cultures in MM-PUh. Induction of esterase activity in inoculated MM-PUh, but not that of protease or urease activities, was observed at 12 h of culture. Esterase activity reached its maximum at 18 h and was maintained at 50% of its maximal activity until the end of the analysis (120 h). The capacity of Alicycliphilus sp. to degrade PU was demonstrated by changes in the PU IR spectrum and by the numerous holes produced in solid PU observed by scanning electron microscopy after bacterial culture. Changes in the PU IR spectra indicate that an esterase activity is involved in PU degradation.

* Corresponding author. Mailing address: Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, 04510 México, D.F. México. Phone: (52) (55) 5622-5280. Fax: (52) (55) 5622-5329. E-mail: hlozat{at}servidor.unam.mx

{triangledown} Published ahead of print on 10 August 2007.

Applied and Environmental Microbiology, October 2007, p. 6214-6223, Vol. 73, No. 19
0099-2240/07/$08.00+0     doi:10.1128/AEM.01230-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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