Extremophile lab, Department. of Microbiology , School of Biology and center of excellence in philogeny of living organisms, College of Science , University of Tehran , Tehran , Iran.
Department of Genetics, Faculty of Science, Shahid Chamran University of Ahvaz, Iran.
Microbial Biotechnology Lab., Dept. of Microbiology, School of Biology, College of Science, University of Tehran, Tehran, Iran
Production of extracellular amylase was demonstrated under conditions of high salinity in aerobically cultivated culture of a newly isolated moderately halophilic Gram-positive coccus, designated strain F in basal medium containing peptone from meat, yeast extract, NaCl (7% w/v) and starch. Biochemical and physiological characterization along with 16S rRNA sequence analysis placed F in the genus Nesterenkonia. The enzyme production was synchronized bacterial growth and reached a maximum level during the early-stationary phase in the basal medium. Maximum yield production was observed when the soluble starch, yeast extract and NaCl (1%, 0.75% and 10% w/v, respectively) were used in the fermentation medium with pH 8.0, inoculated with 7% (v/v) pre-culture medium and incubated in 30°C for 72 h with aeration of 250 rpm (299.25 U/ml).
The potential of different carbohydrates in amylase production was in the order: starch> maltose>dextrin>fructose>lactose=glucose>sodium acetate>sodium citrate. The production yield in the presence of different salts was as follows: NaCl> KCl> NaNO3> Na2SO4. Maximum activity for enzyme was assayed in 3.0 M NaCl, pH: 5-7, and 40°C. α-amylase hydrolyzed starch, dextrin and glycogen to form maltose, maltotriose and maltotetraose as major products, and has no effect on amylose and pullulan as substrates. These results suggest that the amylase secreted by Nesterenkonia sp. strain F is industrially important from the perspective of its tolerance to a broad temperature range and its high tolerance to a wide range of salt concentrations (0–3 M NaCl).