Comparison of Covalent and Noncovalent Immobilization of Malatya Apricot Pectinesterase (Prunus armeniaca L.)

Figures & data

Figure 1. Immobilization of Malatya apricot pectinesterase on porous glass beads.

Table 1. Purification of pectinesterase enzyme isolated from Malatya apricot.

Purification step	Volume (mL)	Total activity (unit)	Total protein (mg)	Specific activity (unit/mg)	Yield %	Purification n-fold
Crude extract	1060	1742.6	298.9	5.83	100	1.0
40-80% (NH4)2SO4 precipitation	125.5	880.76	29.1	30.27	50.5	5.2
Dialysis	122.5	1666.7	23.5	70.92	95.6	12.2

Table 2. Immobilization of PE from Malatya apricot on porous glass beads.

Free enzyme		Immobilized enzyme
Protein (mg/ 2.15 g glass beads) (x)	Specific activity (unit/mg)	Protein in washing (mg) (y)	Bound protein (mg) (x-y = A)	Activity (unit)	Specific activity (unit/mg)	Activity yield (%) ((A/x)x100)
1.92	5.83	0.199	1.721	4.651	2.702	89.64

Table 3. Inactivation rate constants and of free and immobilized apricot PEs.

	Inactivation rate constant, k(x10^3)			Half-life, t1/2 (ln 2/k) (min)
Temperature (°C)	Free PE	Immobilized on porous glass beads	Bentonite-immobilized enzyme	Free PE	Immobilized on porous glass beads	Bentonite-immobilized enzyme
70	2.55	2.46	1.55	271.8	281.7	440
80	2.63	2.59	1.82	263.5	267.6	380
90	3.007	2.65	2.35	230.5	261.5	300

Figure 2. The effect of pH on the activity of free and immobilized apricot PE. Reactions were made with 0.5 mL 0.2 M phosphate buffer (pH 7.5) into 4 mL 1% pectin in 0.2 N NaCl.

Figure 3. The effect of temperature on the activity of free and immobilized apricot PE. Reactions were made with 1% pectin concentration at pH 9.0.

Figure 4. The thermal stability profıle for free apricot PE. Reactions were made with 0.5 mL enzyme in 0.2 M phosphate buffer (pH 7.5) into 4 mL 1% pectin in 0.2 N NaCl at pH 9.0.

Figure 5. The thermal stability profıle for covalently immobilized apricot PE. Reactions were made with 1% pectin concentration and 0.05 g immobilized enzyme dissolved with 0.5 mL 0.2 M sodium phosphate buffer (pH 7.5) at pH 9.0.

Figure 6. The thermal stability profıle for noncovalently immobilized apricot PE. Reactions were made with 1% pectin concentration and 0.05 g immobilized enzyme dissolved with 0.5 mL 0.2 M sodium phosphate buffer (pH 7.5) at pH 9.0.

Table 4. Kinetic properties of free and covalently and noncovalently-immobilized apricot PEs.

Enzyme PE	Km (mM)	Vmax (μmol min^−1 mg^−1)
Free	0.77	1.75
Covalently-immobilized PE	0.71	0.64
Noncovalently-immobilized PE	0.51	14.6

Figure 7. Storage stability of free and immobilized PE from Malatya apricot pulp at 4°C.