Amylases of Potential Industrial Application from Microbial Sources
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Date
2006-07
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Addis Ababa Universty
Abstract
Glucoamylase and alpha amylase producing fungal and bacterial strains were
studied. The fungal isolate previously isolated by Abreham Tesfaye belongs to the
genus Aspergillus and was designated as Aspergillus No 43 (Asp 43). The bacterial
isolate (designated as Bacillus sp CRC) which was isolated from Hot spring around
lake Chitu was Gram positive, rode ,motile catalase positive and central endospor
former. Asp 43 glucoamylase was optimally active at pH 4 and temperature of 65 OC.
where as Bacillus CRC alpha amylase showed maximum activity at a pH range of 5-
6 and temperature of 80 OC. Addition of 5 mM Ca2+ did not affect the temperature
profile of both types of amylases. However the bacterial amylase was Ca dependent
for its themostability, and this enzyme retained about 53 % of its original activity after
3 hr incubation at 80 OC. In addition Bacillus CRC was stable over a broad pH range
retaining more than 80 % of its original activity in the pH range of 4.5 – 8.0 . Asp.43
grown in SSF medium at 25 OC produced maximum enzyme when the moisture
content of the wheat bran used as a sole carbon source was 66.7 %. The optimum
pH and temperature for maximum enzyme production by Bacillus CRC in liquid
medium was 6.0 and 55 OC respectively. Bacillus CRC produced maximum enzyme
when the sole carbon and nitrogen sources were starch and trypton ( at 0.5 and 0.2
% respectively). Enzyme secretion by the fungal and bacterial isolates reached
maximum after 96 and 36 hr of incubation respectively.
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Microbial Sources