Greener Journal of Biological Sciences Vol. 3 (2), pp. 061-073, February 2013.
© 2011 Greener Journals
Thermostable Alpha-Amylase from Geothermal Sites of Ethiopia (Afar Region): Isolation, Purification and Characterization
1Aynadis Tamene Hailemariam, 2Tilahun Bekele Gezmu and 3*Gulelat Desse Haki
1,2Center for Food Science and Nutrition, POBox 1176, Addis Ababa University, Addis Ababa, Ethiopia.
3* Department of Food Science and Technology, University of Botswana, Botswana College of Agriculture, Private Bag 0027, Gaborone, Botswana.
One thousand six hundred and thirty bacterial colonies were isolated from hot springs of Afar region (Ethiopia). Of all the species tested, two bacterial strains designated as AGMSB1 and AGLSB5 were selected and produced the highest level of enzyme with an optimum growth temperature of 55OC and 45OC, respectively. They were identified as rod shaped gram positive bacteria belonging to Bacillus species. The optimum temperature of alpha-amylase produced by AGMSB1 was found to be in the range of 75OC to 95OC with 0.85 U/ml activity at 85OC. The optimum pH was in the range of 5 to 7. The enzyme maintained 78% of its original activity (0.66U/ml) after 60 minutes of incubation at 85OC with more or less stable pH values of 5 to 9. Zn+2 strongly inhibited its activity but it was calcium independent. The optimum temperature of the enzyme produced by AGLSB5 was found to be between 65OC and 85OC with 1.96 U/ml activity at 75OC. The optimum pH was in the range of 5 to 7. The enzyme maintained 60% of its original activity (1.18U/ml) after 50 minutes of incubation at 85OC and it was stable at pH values of 5 to 9. Its activity decreased significantly by the presence of Zn+2 but it was independent of calcium ion.
Keywords: Ethiopia, Afar, Alpha amylase, Hot springs