Burhan Arikan

Alkaline serine protease from halotolerantBacillus licheniformis BA17

An alkaline protease from halotolerantBacillus licheniformis BA17, isolated from Van Lake in Turkey, was purified 5.4 fold with 58% yield. The molecular weight was 19.7 kDa and the optimum temperature and pH were 60°C and 10, respectively. The half-life of the pure enzyme was 38 h, 93 min, 14 min and 6 min at 40, 50, 60 and 70°C, respectively. BA17 protease is very active at 30°C between pH 8.0 and 10. Enzyme activity increased in the presence of Cu+2, Mg+2, Mn+2 and K+1 ions. Enzyme retained activity with 5% SDS (w/v) and 1% Triton X-100 (v/v). Inhibition with PMSF and EDTA suggested that the enzyme is a serine protease and is a metal-activated enzyme. Based on the N-terminal sequence of the first 13 amino acids,B. licheniformis BA17 alkaline protease did not show identity to any of those from otherBacillus species.

Isolation and identification of alkaline protease producer halotolerantBacillus licheniformis strain BA17

An alkaline protease producerBacillus licheniformis strain was isolated from Van Lake in Turkey. The strain is Gram positive, aerobic, motile, sporulating rod-shaped bacterium. Spores were ellipsoidal and positioned central in nonswollen sporangium. The cells were able to grow well at a pH range of 5.7–10. The optimal growth temperature was found to be 37 °C. Growth at a wide range of NaCl concentration (from 0 to 20%) showed that BA17 is halotolerant. Main fatty acid composition of BA17 was anteiso-C15:0 and iso-C15∶0. The strain was presumptively identified asB. licheniformis according to 16S rDNA gene sequence analysis. The most appropriate medium for the growth and protease production is composed of 0.5% yeast extract, 0.5% NaNO3, 0.02% MgSO4\7H2O, 0.1% K2HPO4 and 0.5% maltose. The optimum temperature and pH of the alkaline protease of strain BA17 were found to be 60 °C and pH 11, respectively. The activity was completely lost in the presence of PMSF, suggesting that the preparation contains serine-alkaline protease(s).

Isolation and characterization of a cold-active, alkaline, detergent stable α-amylase from a novel bacterium Bacillus subtilis N8

ABSTRACT A cold-active alkaline amylase producer Bacillus subtilis N8 was isolated from soil samples. Amylase synthesis optimally occurred at 15°C and pH 10.0 on agar plates containing starch. The molecular weight of the enzyme was found to be 205 kDa by performing SDS-PAGE. While the enzyme exhibited the highest activity at 25°C and pH 8.0, it was highly stable in alkaline media (pH 8.0–12.0) and retained 96% of its original activity at low temperatures (10–40°C) for 24 hr. While the amylase activity increased in the presence of β-mercaptoethanol (103%); Ba2+, Ca2+, Na+, Zn2+, Mn2+, H2O2, and Triton X-100 slightly inhibited the activity. The enzyme showed resistance to some denaturants: such as SDS, EDTA, and urea (52, 65, and 42%, respectively). N8 α-amylase displayed the maximum remaining activity of 56% with 3% NaCl. The major final products of starch were glucose, maltose, and maltose-derived oligosaccharides. This novel cold-active α-amylase has the potential to be used in the industries of detergent and food, bioremediation process and production of prebiotics.