biologia - Studia

CHARACTERIZATION OF ALPHA-AMYLASE FROM BACILLUS SUBTILIS STRAIN
The values obtained for V max suggest that the preparation of alpha-amylase
hydrolised the starch with a lower speed, probably because of an excessive dilution
during the resuspension in buffer solution, and because of an inactivation arosen
during handling and storage, on the other hand. In the mean time, the value for K m
indicates a lower affinity of the enzyme for the substrate, which can be explained
by the variations as shape and structure of the alpha-amylase substrate.
Conclusions
1. The amylolytic activity of a Bacillus subtilis strain was tested, and it proved to
have a quite important amylolytic capacity. The enzyme production takes place
constitutively, parallel to the biomass increase. The bacteria culture reached a
constant production efficiency after the lag phase, confirming that the enzyme
production is not correlated with the culture age.
2. The enzyme production proved to be closely related with the cell mass quantity.
The biomass quantity was relatively lower, probably because of a poor aeration, as
the oxygen dissolved in the medium has a limitative influence.
3. The enzymatic preparation obtained after partial purification showed a slightly
lower enzymatic activity than the raw extract, partly because of the starch rests
in the raw extract, due to its low solubility.
4. The kinetic analyse indicated a relatively high value of the Michaelis-Menten
constant, this fact shoving a lower affinity of the enzyme for the substrate,
probably because of the wide dimension range of the substrate. The maximum
rate was relatively low, possibly because of the purification method, whose
efficiency was not good enough.
REFERENCES
Atlas, R.M. (2004). Handbook of Microbiological Media, 3rd edition, CRC Press, New York.
Bahrim, G., Dan, V.(1994). The optimization of biosynthesis conditions for protease-amylase
complex bysp.MIVG 6.61, Proc.8th Nat .Symp. Ind. Microbiol. Biotehnol. (Bucharest),
pp. 237-240.
Baig, M.A., Pazlarova, J., Votruba, J. (1984). Kinetics of α-amylase production in a batch and
fed-batch culture of Bacillus subtilis, Folia Microbiol., 29, 359-364.
Banu, C., Vasu, S., Stoicescu, A. (1987). Biotehnologii în industria alimentară, Ed. Tehnică,
Bucureşti.
Dan, V.(2000). Microbiologia produselor alimentare,vol.2,Ed. S.C. Alma, GalaŃi.
Dan, V., Bahrim, G., Nicolau,A.(1998). CondiŃii de obŃinere a complexului amilazo-proteazic
prin cultivarea tulpinii Bacillus subtilis MIUG 9.61 pe medii semisolide. Lucr. IX Symp.
Microbiol. Biotehnol. (Iaşi), pp. 37-44.
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