Amylase Production by Bacillus Species Isolated from Fermenting Tef and Kocho
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Date
1993-06
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Addis Ababa University
Abstract
Amylase producing bacterial strains associated with
kocho and tef fermentation were isolated. The strain from
fermenting kocho was identified as Bacillus subtilis while
the strain from fermenting tef was identified as Bacillus
licheniformis.
Conditions for the productions of amylases were
investigated. The bacterial strains secreted amylase into
a liquid medium containing 1% soluble starch. When starch
was replaced by disaccharide and monosaccharide, amylase
production was reduced. Amylase production was higher with
unfermented kocho compared to other native straches. Of
the nitrogen sources tested, the greatest growth and amylase
production were obtained with 0.5% peptone. The most
appropriate metal salt for amylase production was found
to be 0.02% MgS04. 7H20ยท Amylase was produced over a wide
pH range (4.5 to 9.5 for Bacillus subtilis and 5 to 10
for Bacillus licheniformis with the maximum activity between
pH 6 and 8. Amylase produci ton was greater at temperatures
from 18 to 24 (room temperature) at 72 hour of cultivation.
The amylases which were found to be extracellular were
optimally active at 400 C and pH 5.6. Bacillus licheniformis
T 31 amylase was also active at pH 8. The amylases of both
organisms retained 100% activities for 1 hour at 60oC. These
enzymes were stable in the pH range of 5.5-8.5. MgS04,CaC12
and BaC12 were found to stimulate amylase activity. The
amylases were stable in 0.5 M NaCl with 64% -78% of their
original activities being. retained after 24h. In addition
to amylase, Bacillus subtilis also produced pullulanse.
Using chromatographic analysis, glucose, maltose and
maltotriose were detected as products of hydrolysis .
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Biology