Isolation and characterization of three thermophilic bacterial strains (lipase, cellulose and amylase producers) from hot springs in Saudi Arabia

Abstract

Three strains of thermophilic bacteria were isolated from two different hot springs in Saudi Arabia. These strains were designated M4 and M5 which were isolated from Al-Khoba hot spring and Sh3 which was isolated from Al-Arida hot spring. Cells are Gram positive-stain, strictly aerobic, grew optimally at pH 7.5 to 8.5 and temperature of 55 to 60°C, and tolerated maximally 10% (w/v) NaCl. The three isolates were lipase, cellulose, and amylase producers with variable degrees of enzymatic activity. They grew on various complex substrates such as yeast extract, carbohydrates and organic acids, which included starch, d-galactose, glutamate, fumarate and acetate. Microscopic observations showed that M4 had a long thick rod and spore former, M5 had a very small short rod, and Sh3 had rod and spore former. Phylogenetic analysis of 16 S rRNA sequence for the 3 strains (M4, M5 and Sh3) revealed that these strains have high sequence similarity with Bacillus sp., Brevibacillus borstelenesis and Deinococus geothermals, respectively.

Key words: Thermophilic bacteria, amylase, lipase, cellulase, hot springs, Saudi Arabia.