Immobilization of Trichoderma harzianum α-amylase on treated wool: optimization and characterization.

α-Amylase from Trichoderma harzianum was covalently immobilized on activated wool by cyanuric chloride. Immobilized α-amylase exhibited 75% of its initial activity after 10 runs. The soluble and immobilized α-amylases exhibited maximum activity at pH values 6.0 and 6.5, respectively. The immobilized enzyme was more thermally stable than the soluble one. Various substrates were hydrolyzed by immobilized α-amylase with high efficiencies compared to those of soluble α-amylase. The inhibition of the immobilized α-amylase by metal ions was low as compared with soluble enzyme. On the basis of the results obtained, immobilized α-amylase could be employed in the saccharification of starch processing.

Purification and characterization of α-Amylase from Miswak Salvadora persica.

BACKGROUND: The miswak (Salvadora persica) is a natural toothbrush. It is well known that very little information has been reported on enzymes in miswak as medicinal plant. Recently, we study peroxidase in miswak. In the present study, the main goal of this work is to purify and characterize α-amylase from miswak. The second goal is to study the storage stability of α-amylase in toothpaste. METHOD: The purification method included chromatography of miswak α-amylase on DEAE-Sepharose column and Sephacryl S-200 column. Molecular weight was determined by gel filtration and SDS-PAGE. RESULTS: Five α-amylases A1, A4a, A4b, A5a and A5b from miswak were purified and they had molecular weights of 14, 74, 16, 30 and 20 kDa, respectively. α-Amylases had optimum pH from 6 to 8. Affinity of the substrates toward all enzymes was studied. Miswak α-amylases A1, A4a, A4b, A5a and A5b had Km values for starch and glycogen of 3.7, 3.7, 7.1, 0.52, 4.3 mg/ml and 5.95, 5.9 4.16, 6.3, 6.49 mg/ml, respectively. The optimum temperature for five enzymes ranged 40°C- 60°C. Miswak α-amylases were stable up to 40°C- 60°C after incubation for 30 min. Ca+2 activated all the miswak α-amylases, while Ni2+, Co+2 and Zn+2 activated or inhibited some of these enzymes. The metal chelators, EDTA, sodium citrate and sodium oxalate had inhibitory effects on miswak α-amylases. PMSF, p-HMB, DTNB and 1,10 phenanthroline caused inhibitory effect on α-amylases. The analysis of hydrolytic products after starch hydrolysis by miswak α-amylases on paper chromatography revealed that glucose, maltose, maltotriose and oligosaccharide were the major products. Crude miswak α-amylase in the toothpaste retained 55% of its original activity after 10 months of storage at room temperature. CONCLUSIONS: From these findings, α-amylases from miswak can be considered as beneficial enzymes for pharmaceuticals. Therefore, we study the storage stability of the crude α-amylase of miswak, which contained the five α-amylases, in toothpaste. The enzyme in the toothpaste retained 55% of its original activity after 10 months of storage at room temperature.