RESUMO
The physicochemical characterization and emulsifying functional properties of a novel exopolysaccharide (EPS) produced by haloarchaea Haloferax mucosum (DSM 27191) were investigated. This biopolymer has a high molecular weight of 152â¯kDa and important protein content of 10%. Different culture media compositions were investigated taking the ATCC 2185 medium as a base and supplementing with varying concentrations of yeast extract and glucose or sucrose as carbon sources to produce the EPS in a liquid medium. The highest EPS production (7.15⯱â¯0.44â¯g/L) was obtained at 96â¯h. EPS aqueous dispersions showed a non-Newtonian rheological behavior which was well fitted to the Cross equation. The EPS (at 0.32% w/w) was capable of stabilizing water-in-oil emulsions with different nonpolar solvents, including n-hexane, kerosene, chloroform, castor oil and mineral oil. EPS retained its emulsifying activity after to be incubated for one hour in a wide range of temperatures (25, 40, 70 and 100⯰C), pH (4, 6.5, 7 and 12) and NaCl concentrations (0, 2.0 and 4.0â¯M). The viscoelastic behavior and stability of hexane-in-water emulsion were examined through oscillatory shear measurements.
Assuntos
Emulsões/química , Haloferax/metabolismo , Polissacarídeos Bacterianos/biossíntese , Polissacarídeos Bacterianos/química , Biomassa , Biopolímeros/biossíntese , Biopolímeros/química , Meios de Cultura/química , Haloferax/crescimento & desenvolvimento , Concentração de Íons de Hidrogênio , Peso Molecular , Reologia , Temperatura , ViscosidadeRESUMO
The phylogenetic affiliations of organisms responsible for aerobic CO oxidation in hypersaline soils and sediments were assessed using media containing 3.8 M NaCl. CO-oxidizing strains of the euryarchaeotes, Haloarcula, Halorubrum, Haloterrigena and Natronorubrum, were isolated from the Bonneville Salt Flats (UT) and Atacama Desert salterns (Chile). A halophilic euryarchaeote, Haloferax strain Mke2.3(T), was isolated from Hawai'i Island saline cinders. Haloferax strain Mke2.3(T) was most closely related to Haloferax larsenii JCM 13917(T) (97.0% 16S rRNA sequence identity). It grew with a limited range of substrates, and oxidized CO at a headspace concentration of 0.1%. However, it did not grow with CO as a sole carbon and energy source. Its ability to oxidize CO, its polar lipid composition, substrate utilization and numerous other traits distinguished it from H. larsenii JCM 13917(T), and supported designation of the novel isolate as Haloferax namakaokahaiae Mke2.3(T), sp. nov (= DSM 29988, = LMG 29162). CO oxidation was also documented for 'Natronorubrum thiooxidans' HG1 (Sorokin, Tourova and Muyzer 2005), N. bangense (Xu, Zhou and Tian 1999) and N. sulfidifaciens AD2(T) (Cui et al. 2007). Collectively, these results established a previously unsuspected capacity for extremely halophilic aerobic CO oxidation, and indicated that the trait might be widespread among the Halobacteriaceae, and occur in a wide range of hypersaline habitats.
Assuntos
Monóxido de Carbono/metabolismo , Haloferax , Salinidade , Cloreto de Sódio/metabolismo , Microbiologia do Solo , Aerobiose , Chile , DNA Ribossômico/genética , Genoma Arqueal/genética , Sedimentos Geológicos/microbiologia , Haloferax/genética , Haloferax/isolamento & purificação , Haloferax/metabolismo , Oxirredução , Filogenia , RNA Ribossômico 16S/genética , Solo/químicaRESUMO
Haloferax gibbonsii strain ARA6 is a haloarchaea isolated from saline saltern samples from Vermelha lake, located in Araruama region, Rio de Janeiro, Brazil. Its genome displays 66,2% G+C content and is composed by one circular chromosome of 2,945,391 bp and four circular plasmids comprising 993,063 bp. This genomic information shows H. gibbonsii's potential for biotechnological applications and can also contribute to assign evolutionary traits in the genus Haloferax.