title: Enhancement of Alkaline Protease Activity and Stability via Covalent Immobilization onto Hollow Core-Mesoporous Shell Silica Nanospheres.
abstract: The stability and reusability of soluble enzymes are of major concerns, which limit their industrial applications. Herein, alkaline protease from Bacillus sp. NPST-AK15 was immobilized onto hollow core-mesoporous shell silica (HCMSS) nanospheres. Subsequently, the properties of immobilized proteases were evaluated. Non-, ethane- and amino-functionalized HCMSS nanospheres were synthesized and characterized. NPST-AK15 was immobilized onto the synthesized nano-supports by physical and covalent immobilization approaches. However, protease immobilization by covalent attachment onto the activated HCMSS-NH₂ nanospheres showed highest immobilization yield (75.6%) and loading capacity (88.1 μg protein/mg carrier) and was applied in the further studies. In comparison to free enzyme, the covalently immobilized protease exhibited a slight shift in the optimal pH from 10.5 to 11.0, respectively. The optimum temperature for catalytic activity of both free and immobilized enzyme was seen at 60 °C. However, while the free enzyme was completely inactivated when treated at 60 °C for 1 h the immobilized enzyme still retained 63.6% of its initial activity. The immobilized protease showed higher V(max), k(cat) and k(cat)/K(m), than soluble enzyme by 1.6-, 1.6- and 2.4-fold, respectively. In addition, the immobilized protease affinity to the substrate increased by about 1.5-fold. Furthermore, the enzyme stability in various organic solvents was significantly enhanced upon immobilization. Interestingly, the immobilized enzyme exhibited much higher stability in several commercial detergents including OMO, Tide, Ariel, Bonux and Xra by up to 5.2-fold. Finally, the immobilized protease maintained significant catalytic efficiency for twelve consecutive reaction cycles. These results suggest the effectiveness of the developed nanobiocatalyst as a candidate for detergent formulation and peptide synthesis in non-aqueous media.
authors: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia. ashebl@ksu.edu.sa.|Department of Chemistry of Natural and Microbial Products, Pharmaceutical Industries Research Division, National Research Center, El-Buhouth St., Dokki, Cairo 12311, Egypt. ashebl@ksu.edu.sa.
authors: Abdelnasser Salah Shebl
authors: AS
authors: Ibrahim
authors: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia. aaasalah98@yahoo.com.
authors: Ali A
authors: AA
authors: Al-Salamah
authors: King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451, Saudi Arabia. aamohammad@ksu.edu.sa.|Central Metallurgical Research and Development Institute, Helwan, Cairo 11421, Egypt. aamohammad@ksu.edu.sa.
authors: Ahmed M
authors: AM
authors: El-Toni
authors: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia. kalmaary@ksu.edu.sa.
authors: Khalid S
authors: KS
authors: Almaary
authors: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia. mohamedmicro32@yahoo.com.
authors: Mohamed A
authors: MA
authors: El-Tayeb
authors: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia. alzeeem95@yahoo.com.
authors: Yahya B
authors: YB
authors: Elbadawi
authors: Institute of Technical Microbiology, Hamburg University of Technology, Hamburg 21073, Germany. antranikian@tuhh.de.
authors: Garabed
authors: G
authors: Antranikian
mesh_terms: D001407:Bacillus / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D010450:Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism; D054118:Nanospheres / Q000737:chemistry*; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D004800:Enzymes, Immobilized; D012822:Silicon Dioxide; D010450:Endopeptidases; C087822:alkaline protease
keywords: alkaline protease; alkaliphiles; detergents; hollow core-mesoporous shell silica nanospheres; immobilization; nanotechnology