i CHARACTERIZATION AND IMMOBILIZATION OF PARTIALLY PURIFIED POLYGALACTURONASE FROM ASPERGILLUS NIGER (SA6) FOR INDUSTRIAL USE
i CHARACTERIZATION AND IMMOBILIZATION OF PARTIALLY PURIFIED POLYGALACTURONASE FROM ASPERGILLUS NIGER (SA6) FOR INDUSTRIAL USE
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Date
2008-05
Authors
LAWAL, BUGA MOHAMMED
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Abstract
ABSTRACT
Polygalacturonase (PG) was isolated from Aspergillus niger(A.
niger) SA6. The enzyme was partially purified and characterized. It
was then immobilized by entrapment using calcium alginate. The
enzyme showed two bands on SDS-PAGE suggesting the
presence of an endo and exo PG with apparent molecular
weights of 35KDa and 40KDa respectively. The PG was purified 9
fold with a yield of 0.18 % and a specific activity of 246
mole/min/mg. The KM and Vmax values of the enzyme were 2.74
mg/ml and 0.78mole/min/mg respectively. The optimum
temperature and optimum pH of the enzyme were 40oC and 4.5
respectively. The native PG was found to be more stable to
temperature changes than to pH changes. Both the Vmax and KM
of the native PG increased in the presence of EDTA and the
following divalent cations Mg2+,Ca2+ and Mn2+. The increase was
more pronounced in the presence of Ca2+ ion. The activation
energy (Ea) of native PG was 259.19 Cal/degree/mole. The Dixon
Plot of the enzyme gave pKa values of 4.9 and 5.6 suggesting
Glutamic acid and histidine at the active site of the enzyme. The
apparent KM and Vmax of the immobilized PG were 11.1mg/ml and
1.65 mole/min/mg respectively. The optimum pH and optimum
temperature of the immobilized PG were 4.5 and 40oC
respectively. Immobilized PG was more resistant to changes in pH
than to temperature. The activity of the immobilized PG reduced
to 34.56 % and 14.81 % of the initial activity in the second and third
catalytic cycles respectively. The half-life of the enzyme at 40oC
and the activity lost per minute on thermal storage were 10
minutes and 0.0213 μmole of D- galacturonic acid. These findings
present novel information on the physico- chemical
characteristics of the native and immobilized Polygalacturonase
isolated from a local strain of Aspergillus niger (SA6).
Description
DEPARTMENT OF BIOCHEMISTRY
FACULTY OF SCIENCE
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
Keywords
CHARACTERIZATION,, IMMOBILIZATION,, PARTIALLY,, PURIFIED,, POLYGALACTURONASE,, ASPERGILLUS,, NIGER,, (SA6), INDUSTRIAL,, USE