title: Immobilization of cross-linked phenylalanine ammonia lyase aggregates in microporous silica gel.
abstract: A separable and highly-stable enzyme system was developed by adsorption of phenylalanine ammonia lyase (PAL) from Rhodotorula glutinis in amino-functionalized macroporous silica gel and subsequent enzyme crosslinking. This resulted in the formation of cross-linked enzyme aggregates (PAL-CLEAs) into macroporous silica gel (MSG-CLEAs). The effect of adsorptive conditions, type of aggregating agent, its concentration as well as that of cross-linking agent was studied. MSG-CLEAs production was most effective using ammonium sulfate (40%-saturation), followed by cross-linking for 1 h with 1.5% (v/v) glutaraldehyde. The resulting MSG-CLEAs extended the optimal temperature and pH range compared to free PAL and PAL-CLEAs. Moreover, MSG-CLEAs exhibited the excellent stability of the enzyme against various deactivating conditions such as temperature and denaturants, and showed higher storage stability compared to the free PAL and the conventional PAL-CLEAs. Such as, after 6 h incubation at 60°C, the MSG-CLEAs still retained more than 47% of the initial activity whereas PAL-CLEAs only retained 7% of the initial activity. Especially, the MSG-CLEAs exhibited good reusability due to its suitable size and active properties. These results indicated that PAL-CLEAs on MSG might be used as a feasible and efficient solution for improving properties of immobilized enzyme in industrial application.
authors.affiliation: Research Center for Fermentation Engineering of Hebei, College of Bioscience and Bioengineering, Hebei University of Science and Technology, Shijiazhang, P R China ; National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, HaiDian District, Beijing, P R China ; Key Laboratory of Industry Microbiology, Ministry of Education, Tianjin University of Science and Technology, Tai Da Development Area, Tianjin, P R China.
authors.forename: Jian Dong
authors.initials: JD
authors.lastname: Cui
authors.forename: Lian Lian
authors.initials: LL
authors.lastname: Li
authors.forename: Hong Jie
authors.initials: HJ
authors.lastname: Bian
mesh_terms: D000327:Adsorption; D003432:Cross-Linking Reagents / Q000737:chemistry; D004789:Enzyme Activation; D004800:Enzymes, Immobilized / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010650:Phenylalanine Ammonia-Lyase / Q000737:chemistry*; D016062:Porosity; D012248:Rhodotorula / Q000201:enzymology; D058428:Silica Gel / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics
chemical_list: D003432:Cross-Linking Reagents; D004800:Enzymes, Immobilized; D058428:Silica Gel; D010650:Phenylalanine Ammonia-Lyase