Mise en évidence des activités hydrolytiques extracellulaires de microorganismes halophiles et halotolérants des environnements hypersalins sahariens

Abstract

Halophilic and halotolerant microorganisms in hypersaline environments have developed strategies to adapt to environmental constraints. They thus present original biomolecules, in particular enzymes which enable them to develop optimally in their biotopes. The exploitation of these microorganisms and their molecules is a boon for biotechnology. The objective of this study is to demonstrate extracellular hydrolytic activities in halophilic and halotolerant microorganisms of sebkha Melghir and chott Merouane (wilaya of El Oued), and chott Aïn El Beida (wilaya of Ouargla). This work resulted in the isolation of seventy-two strains from brine and sediment samples. A preliminary characterization based on cultural, morphological, biochemical and physiological aspects is carried out. 29 pigmented, Gram-negative and extreme halophilic strains (optimum at 20% (w/v) salt) possess the properties of haloarchaea. The remainder of the isolates are distributed between moderate halophiles and halotolerants, and often Grampositive. The spherical cellular form is predominant. All strains have a broad growth temperature range with an optimum at 37°C or 45°C; They are moderate mesophiles or thermophiles. About 50 strains have extracellular hydrolases, dominated by the hydrolysis capacity of gelatin. However, amylolytic activity appears to be more important in strains of Archaea. In addition, many isolates produce up to four types of hydrolases.