الفهرس 
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Abstract
The aim of the present thesis was to optimize, isolate, purify and immobilize α-glucosidase from P. chrysogenum. The results in the present investigation showed the following:
* The optimal pH and temperature of production were 7 and 35 ºC. Also, the optimal incubation period was 7th day of incubation.
* The effect of different carbon sources showed that sucrose expressed the highest enzyme production. The concentration 1.5 % w/v of sucrose was the optimal concentration.
* The effect of different nitrogen sources showed that NaNO3 expressed the highest production. Also, the results showed that the 2 % NaNO3 was the highest concentration for α-glucosidase production.
* α-glucosidase was isolated and purified using 85 % ammonium sulphate, DEAE-cellulose and Sephadex G-200. The obtained results indicate that the enzyme was purified with 360 units mg-1 protein and 52.9 fold. The molecular weight of the enzyme was 68 KDa.
* The optimal pH and temperature of α-glucosidase activity were 5 and 40 ºC.
* The thermostability of α-glucosidase was studied at 60 ºC in the presence of dextrose, sucrose and raffinose and the results showed a reduction in the relative activity with increasing the time. Raffinose was the least effective compound.
* The thermostability of α-glucosidase was studied at 60 ºC in the presence of trehalose and the results revealed that thermostability in the absence of trehalose was lower than in its presence at all the exprimental time intervals.
* The chelating agents namely α-α-dipyridyl and EDTA inhibited α-glucosidase activity. The IC50 for the two compounds were 17.8 and 17.1 mM, respectively.
* H2O2 inhibited α-glucosidase activity at all the tested concentrations and the IC50 was 22.9 % v/v.
Summary
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* Studying the effect of amino acids on enzyme activity revealed that cysteine, glycine, arginine and methionine enhanced the enzyme activity with different rates at the lower concentrations.
* Studying the effect of thiol containing compounds revealed that reduced glutathione (GSH) and thioglycolate enhanced α-glucosidase at the lower concentrations and inhibited the activity at the higher one.
* Studying the effect of various surfactants such as T60, T80, Triton x-100, cefridime and SDS revealed that all surfactants increased the activity of α-glucosidase and highest relative activity was observed in presence of SDS.
* The effect of ATP on α-glucosidase indicates that the activity increased gradually up to 1.2 mM then the activity decreased.
* Differnt organic solvents such as methanol, ethanol, propanol and hexane increased the activity of α-glucosidase at all concentrations.
* The reagent of active groups (NAI and DC) inhibited the enzyme activity. The IC50 for the two compounds were 4.9 and 7 mM, respectively.
* The phytohormones such as kinetin, NAA, jasmonic acid and BAP enhanced α-glucosidase activity with variable ranges at the lower concentrations.
* The extracts from Trigonella foenum-grecum, Sinapis arvensis, Cucurbita moschata, Apium crispum and Lepidium sativum expressed an inhibitory effect on α-glucosidase activity. The results show that Sinapis arvensis extract was the best for inhibiting α-glucosidase activity (IC50 = 65.3 μg ml-1) whereas the least effective extract was Lepidium sativum (IC50 = 97.9 μg ml-1)
* α-glucosidase was immobilized on Ca-alginate, silica gel and chitosan. The results show that chitosan was the best one for α-glucosidase immobilization followed by alginate and silica gel.
* The effect of protein loading on immobilization efficiency was investigated using different concentrations of α-glucosidase reveal continuous increase in α-glucosidase activity.
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* The influence of calcium chloride on α-glucosidase revealed increase in immobilization efficiency (%) of α-glucosidase with increasing the concentration up to 0.6 mM after which immobilization efficiency declined continuously.
* The results showed that storage stability of the immobilized α-glucosidase was higher than the free enzyme at 4 °C and 25 °C. Also, studying the effect of substrate concentrations on the activity of free, entrapped and cross-linked α-glucosidase showed different values for Vmax and Km.
* The effect of different metal ions on α-glucosidase activity indicates that MgCl2 did not show remarkable effect however, Ca2+ activated α-glucosidase. CoCl2, HgCl2, CdCl2 and NiCl2 inhibited the α-glucosidase activity.
* The reuse of entrapped and cross-linked α-glucosidase revealed that the cross-linked α-glucosidase expressed higher residual activity compared with the entrapped one throughout the nine cycles.
* The desorpivity percent of both entrapped and cross-linked α-glucosidase revealed that the entrapped α-glucosidase showed higher desorptivity compared to the cross-linked α-glucosidase.