title: Thermostabilization of Aspergillus oryzae β-d-galactosidase.
abstract: The thermal stability of the Aspergillus oryzae β-d-galactosidase (β-gal) was evaluated at 60 °C. The stability of β-gal was dependent on the pH, buffer, and additives. The β-gal exhibited its highest thermal stability in a 0.02 M phosphate buffer pH 6. Among all the tested additives, galactose, a competitive inhibitor of β-gal, was the upmost thermal stabilizer. A 0.15 M galactose solution caused β-gal to retain a whole of 98.65% of its initial activity after incubation at 60 °C for 2 H. The second best thermal stabilizer of β-gal was raffinose. A 0.15 M raffinose-β-gal mixture retained 84.41% of its initial activity after incubation at 60 °C for 2 H, whereas the control retained only 61.02%. The results of this study also revealed that all the tested positively charged polymers (diethylaminoethyl [DEAE] dextran and polyethyleneimine [PEI] 800, 2,000, 750,000 Da) significantly destabilized β-gal. However, these positively charged polymers exerted different effects on the β-gal's activity. PEI 750,000 significantly activated the enzyme, while DEAE dextran and PEI 800 did not exert any significant effects on the β-gal's activity. Nevertheless, PEI 2,000 significantly activated the enzyme.
authors.affiliation: Department of Natural and Microbial Chemistry, National Research Center, Dokki, Cairo, Egypt.|Centre of Scientific Excellence, Group of Encapsulation and Nanobiotechnology, Cairo, Egypt.
authors.forename: Marwa I
authors.initials: MI
authors.lastname: Wahba
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D001236:Aspergillus oryzae / Q000201:enzymology*; D002021:Buffers; D002241:Carbohydrates / Q000494:pharmacology; D004795:Enzyme Stability / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D011108:Polymers / Q000494:pharmacology; D013696:Temperature; D001616:beta-Galactosidase / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D002021:Buffers; D002241:Carbohydrates; D011108:Polymers; D001616:beta-Galactosidase
keywords: galactose; polymers; raffinose; thermal stabilization; β-d-galactosidase