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Optimization of the
industrial production of bacterial alpha amylase in Egypt.
IV. Fermentor production and characterization of the enzyme
of two strains of Bacillus subtilis and Bacillus
amyloliquefaciens
O. El-Tayeb1*, F. Mohammad2, A. Hashem1
and M. Aboulwafa3
1Department
of Microbiology and Immunology, Faculty of Pharmacy, Cairo
University Kasr El-Aini street, Cairo, Egypt, 11562.
2Department
of Chemical Engineering and Pilot Plant, National Research
Centre, Egypt.
3Department
of Microbiology and Immunology, Faculty of Pharmacy, Ain
Shams University, Cairo, Egypt.
*Corresponding author. E-mail:
omtayeb@link.net.
Accepted
26 October, 2007 |
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Production of alpha amylase using amplified variants of
Bacillus subtilis (strain SCH) and of Bacillus
amyloliquefaciens (strain 267CH) was conducted in a
bioreactor with multiprotein-mineral media. The time course
of fermentation in a bioreactor revealed that the highest
yield (about 8 x 104 U/ml within 60 h) by strain
SCH was obtained by applying: 3.5% initial starch, 2%
additional starch after 19 h, 3 vvm aeration and 300 rpm
agitation. The highest yield (about 19 x 104 U/ml
within 100 h) by strain 267CH was obtained by applying: 2.5%
initial starch, 2% additional starch after 24 h, 3 vvm
aeration, and 300 rpm agitation with the productivity after
60 h reaching only about 14 x 104 U/ml.
Production occurred in both the logarithmic and
postlogarithmic phases of growth. Maximum consumption of
starch and protein occurred during the first day of
incubation. The optical density peak coincided with enzyme
production peak in case of strain SCH and preceded that of
enzyme production in case of strain 267CH. The alpha amylase
produced by the two strains was shown to be of the
liquefying and not the saccharifying type. Both enzymes
liquefied starch to a dextrose equivalent of about 15 - 17
at 95oC hence they are classified among
thermostable alpha amylases. They exhibited broad pH and
temperature activity profiles. The optimum pH for activity
was 4 - 7 for alpha amylase produced by strain SCH and 4 - 8
for alpha amylase produced by strain 267CH while the optimum
temperatures for their activities were in the range 37 -75oC
at 0.5% starch and in the range 85 - 95oC at 35%
starch.
Key
words: Production kinetics, process modeling,
fermentation, bacterial amylase, biotechnology. |
