A bacterial strain E21 was isolated from a sample of water collected in the salt lake located close to Ain Salah, Algeria. The analysis of 16S rRNA gene sequence had indicated that the strain had 93 % sequence similarity with the genus Natrialba sp. strain E21 (GenBank, FR750525.1) and was considered extremely halophilic. Production of biosurfactant by the strain E21 with free and entrapped cells was investigated using soluble starch in the saline conditions. Biosurfactant synthesis was followed by measuring the surface tension and emulsifying index 9 days under optimal conditions (40 °C, pH 7). Some diffusional limitations in alginate and agar beads affected the kinetics of biosurfactant production when compared to that obtained with free cells culture. The minimum values of surface tension were 27 and 30 mN m(-1) achieved after 9 days with free and immobilized cells, respectively, while the corresponding maximum E24 values were 65.3 and 62.3 %, respectively. The re-use of bacterial cells along with the limited cell losses provided by the immobilized system might lead to significant reduction of the biosurfactant production cost.

At the limits of life, hyper-saline aquatic ecosystems; Chott and Sebkha are a model of choice of extreme environments, housing a halophilic microflora that had to adapt to these conditions. In Algeria, these ecosystems are poorly studied. However, our study was carried out on the waters of Chott Tinsilt and Sebkha El Malah. The study of this microflora revealed the presence of a significant morphological, physiological and metabolic diversity. The molecular study allowed us to access to a phylogenetic affiliation including an Archean Species (ATS1) and 7 bacterial species (A1, A2, A3, A4, B1, B4, B5). The results showed that these isolates were related to the genera Haloferax (for the strain ATS1) and Halomonas (strains A1, A2 and A4), Staphylococcus (strain A3), Salinivibrio (strain B1), Planococcus (strain B4) and Halobacillus (strain B5). Most isolates produced hydrolases at high salt concentrations. The Production yields obtained are very promising for applications in the biotechnology and industrial microbiology.