Characterization of a native cellulase activity from an anaerobic thermophilic hydrogen-producing bacterium Thermosipho sp. strain 3
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A bacterial strain, designated as strain 3 and identified as a member of the Thermosipho species on the basis of its phenotypic and genotypic characteristics, was isolated from a deep sea hydrothermal vent. Sequence analysis of the 16S rRNA gene revealed that its closest neighbor was Thermosipho africanus (99.5 %). This isolate Thermosipho sp. strain 3 (DSM 27729), a thermophilic, anaerobic, fermentative hydrogen-producing bacterium, produced a thermostable endocellulase that hydrolyzes carboxymethylcellulose (CMC) and β-glucan. The cellulase was purified and its activity characterized. The estimated molecular weight of the protein was about 40 kDa as determined by gel-filtration chromatography, SDS-PAGE and zymogram analyses. The optimal cellulase activity was at pH 5.5 and at a temperature of 80 °C. The enzyme was thermostable with about 50 % residual activity after 48 h and 4 h at 60 °C and 70 °C, respectively. Interestingly, endocellulase activity was increased about 2-fold by 5 mM MnCl2. MALDI-TOF PMF and the N-terminal amino acid sequence analyses of the purified enzyme revealed the extensive homology of the protein with a glycoside hydrolase family protein from Thermosipho africanus (NCBI protein accession number: 419759359; UniProt: K2PFP0).
KeywordsHydrogen Cellulase Carboxymethylcellulose Thermophilic Hydrothermal vent
This research has been supported by the framework project “Metodologie innovative per la produzione di idrogeno da processi biologici” of the Italian Ministry for Education, University and Scientific Research (F.I.S.R. D.M. 17/02/2002). The authors thank Dr. Javier Pascual for phylogenetic analyses.
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