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A proteolytic thermophilic bacterial strain, designated as strain SF03, was isolated from sewage sludge in Singapore. Strain SF03 is a strictly aerobic, Gram stain-positive, catalase-positive, oxidase-positive, and endospore-forming rod. It grows at temperatures ranging from 35 to 65 degrees C, pH ranging from 6.0 to 9.0, and salinities ranging from 0 to 2.5%. Phylogenetic analyses revealed that strain SF03 was most similar to Saccharococcus thermophilus, Geobacillus caldoxylosilyticus, and G. thermoglucosidasius, with 16S rRNA gene sequence identities of 97.6, 97.5 and 97.2%, respectively. Based on taxonomic and 16S rRNA analyses, strain SF03 was named G. caldoproteolyticus sp. nov. Production of extracellular protease from strain SF03 was observed on a basal peptone medium supplemented with different carbon and nitrogen sources. Protease production was repressed by glucose, lactose, and casamino acids but was enhanced by sucrose and NH4Cl. The cell growth and protease production were significantly improved when strain SF03 was cultivated on a 10% skim-milk culture medium, suggesting that the presence of protein induced the synthesis of protease. The protease produced by strain SF03 remained active over a pH range of 6.0-11.0 and a temperature range of 40-90 degrees C, with an optimal pH of 8.0-9.0 and an optimal temperature of 70-80 degrees C, respectively. The protease was stable over the temperature range of 40-70 degrees C and retained 57 and 38% of its activity at 80 and 90 degrees C, respectively, after 1 h.

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Abstract:In this study, Ce 1x Sm x O 2x/2 ceramics were synthesized by sol-gel route and solid state sintering method. The phase structure was analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The morphologies of the synthesized powders and the corresponding bulk samples were observed using scanning electron microscopy (SEM). Their thermal diffusivities and thermal expansion coefficients were measured by the laser-flash method and the pushing-rod method, respectively. Results show that pure Ce 1x Sm x O 2x/2 powders with single fluorite structure are synthesized successfully, and their microstructures of the corresponding bulk samples are very dense. With the increase of Sm 2 O 3 content, their thermal expansion coefficients decrease due to the higher electro-negativity of Sm 3+ ions as compared with that of Ce 4+ ions. Their thermal conductivities at 1000 ℃ lie in the range of 1.62-2.02 W/(m·K) due to the phonon scattering caused by the substituted atoms and oxygen vacancies. The Ce 1x Sm x O 2x/2 ceramics can be used as ceramic candidates for novel thermal barrier coatings (TBCs).