title: Cross-linked enzyme aggregates of phenylalanine ammonia lyase: novel biocatalysts for synthesis of L-phenylalanine.
abstract: Cross-linked enzyme aggregates of phenylalanine ammonia lyase (PAL-CLEAs) from Rhodotorula glutinis were prepared. The effects of the type of aggregating agent, its concentration, and that of cross-linking agent were studied. PAL-CLEAs production was most effective using ammonium sulfate (40 % saturation), followed by cross-linking for 1 h with 0.2 % (v/v) glutaraldehyde. Moreover, the storage and operational stability of the resulting PAL-CLEAs were also investigated. Compared to the free enzyme, the PAL-CLEAs exhibited the expected increased stability of the enzyme against various deactivating conditions such as pH, temperature, denaturants, and organic solvents and showed higher storage stability than its soluble counterpart. Additionally, the reusability of PAL-CLEAs with respect to the biotransformation of L-phenylalanine was evaluated. PAL-CLEAs could be recycled at least for 12 consecutive batch reactions without dramatic activity loss, which should dramatically increase the commercial potential of PAL for synthesis of L: -phenylalanine. To the best of our knowledge, this is the first report of immobilization of PAL as cross-linked enzyme aggregates.
authors.affiliation: Research Center for Fermentation Engineering of Hebei, College of Bioscience and Bioengineering, Hebei University of Science and Technology, Shijiazhang, People's Republic of China. cjd007cn@163.com
authors.forename: Jian-Dong
authors.initials: JD
authors.lastname: Cui
authors.forename: Si
authors.initials: S
authors.lastname: Zhang
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Sun
mesh_terms: D055162:Biocatalysis; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004795:Enzyme Stability / Q000187:drug effects; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D009930:Organic Chemicals / Q000737:chemistry / Q000494:pharmacology; D010649:Phenylalanine / Q000096:biosynthesis*; D010650:Phenylalanine Ammonia-Lyase / Q000737:chemistry* / Q000378:metabolism*; D011489:Protein Denaturation / Q000187:drug effects; D012248:Rhodotorula / Q000201:enzymology; D012997:Solvents / Q000737:chemistry / Q000494:pharmacology; D013696:Temperature
chemical_list: D003432:Cross-Linking Reagents; D004800:Enzymes, Immobilized; D009930:Organic Chemicals; D012997:Solvents; D010649:Phenylalanine; D010650:Phenylalanine Ammonia-Lyase