A wide array of extreme halophilic enzymes derived from solar salterns of Bejaia in the north of Algeria: a focus on amylases from Haloarcula sp. strain ICHS1, Natrinema altunense strain MS1 and Haloferax gibbonsii strain MS2.

The biodiversity of extreme halophilic enzymes produced in three different solar salterns in the Bejaia region of northern Algeria was investigated, with a focus on the characterization of amylases. Generally, 101-103 CFU/g (ml) of extreme halophiles have been detected. 126 extreme halophilic microorganisms have been isolated. The isolates were found to produce several enzymes: amylase, esterase, gelatinase, laccase, lipase, caseinase, and cellulase. Four amylase-producing strains were identified as Haloarcula sp. strain ICHS1, Natrinema altunense strain MS1, Haloferax gibbonsii strain MS2, and Haloferax sp. strain MS3. Three different extracellular amylases were produced and characterized. Notably, amylase production was induced by the presence of starch. The MS2 enzyme requires 10% of NaCl for optimal activity, MS1 and ICHS1 amylases require 15% and 25% of NaCl, respectively. All three enzymes were characterized as thermophilic amylases that exhibited optimal activity at elevated temperatures (50-55 °C), and as acidophilic enzymes (optimal pH between 4 and 5). MS2 amylase was stimulated by the presence of Ca2+, Cu2+, Mn2+, and Zn2+; while, Fe2+ and Mg2+ had a negative impact. ICHS1 amylase was stimulated by Ca2+, Cu2+, and Fe2+, however Zn2+, Mg2+, and Mn2+ had inhibitory effects. In contrast, all tested ions decreased the activity of MS1 amylase. All amylases showed excellent resistance to organic solvents. This combination of properties suggests potential applications for these enzymes in biotechnology, particularly in extreme environments, as well as in fundamental research into the adaptations of halophilic enzymes and to elucidate differences between salt-dependent and salt-independent halophilic enzymes.