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Applied and Environmental Microbiology, December 2007, p. 7725-7731, Vol. 73, No. 23
0099-2240/07/$08.00+0     doi:10.1128/AEM.01509-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Purification and Characterization of Two Highly Thermophilic Alkaline Lipases from Thermosyntropha lipolytica{triangledown}

Moh'd A. Salameh{dagger} and Juergen Wiegel*

Department of Microbiology, University of Georgia, Athens, Georgia 30602-2605

Received 4 July 2007/ Accepted 25 September 2007

Two thermostable lipases were isolated and characterized from Thermosyntropha lipolytica DSM 11003, an anaerobic, thermophilic, alkali-tolerant bacterium which grows syntrophically with methanogens on lipids such as olive oil, utilizing only the liberated fatty acid moieties but not the glycerol. Lipases LipA and LipB were purified from culture supernatants to gel electrophoretic homogeneity by ammonium sulfate precipitation and hydrophobic interaction column chromatography. The apparent molecular masses of LipA and LipB determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 50 and 57 kDa, respectively. The temperature for maximal activity of LipA and LipB was around 96°C, which is, so far as is known, the highest temperature for maximal activity among lipases, and the pH optima for growth determined at 25°C (pH25°C optima) were 9.4 and 9.6, respectively. LipA and LipB at 100°C and pH25°C 8.0 retained 50% activity after 6 and 2 h of incubation, respectively. Both enzymes exhibited high activity with long-chain fatty acid glycerides, yielding maximum activity with trioleate (C18:1) and, among the p-nitrophenyl esters, with p-nitrophenyl laurate. Hydrolysis of glycerol ester bonds occurred at positions 1 and 3. The activities of both lipases were totally inhibited by 10 mM phenylmethylsulfonyl fluoride and 10 mM EDTA. Metal analysis indicated that both LipA and LipB contain 1 Ca2+ and one Mn2+ ion per monomeric enzyme unit. The addition of 1 mM MnCl2 to dialyzed enzyme preparations enhanced the activities at 96°C of both LipA and LipB by threefold and increased the durations of their thermal stability at 60°C and 75°C, respectively, by 4 h.

* Corresponding author. Mailing address: Dept. of Microbiology, University of Georgia, 1000 Cedar St., Athens, GA 30602-2605. Phone and fax: (706) 542-2651. E-mail: jwiegel{at}uga.edu

{triangledown} Published ahead of print on 12 October 2007.

{dagger} Present address: Cancer Research Center, Mayo Clinic, Jacksonville, FL 32224.

Applied and Environmental Microbiology, December 2007, p. 7725-7731, Vol. 73, No. 23
0099-2240/07/$08.00+0     doi:10.1128/AEM.01509-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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