Immobilization of (R)- and (S)-amine transaminases on chitosan support and their application for amine synthesis using isopropylamine as donor
•Several transaminases successfully immobilized on chitosan.•Improvement of stability, recycling and storage achieved.•Activation upon immobilization observed.•Divinylsulfone as alternative linker molecule, besides glutaraldehyde, used.•Asymmetric amine synthesis using isopropylamine as donor achieved.
Transaminases from Aspergillus fumigatus ((R)-selective, AspFum), Ruegeria pomeroyi ((S)-selective, 3HMU) and Rhodobacter sphaeroides 2.4.1 ((S)-selective, 3I5T) were immobilized on chitosan with specific activities of 99, 157, and 163 U/g and acceptable yields (54, 21, and 23%, respectively) for glutaraldehyde (GA) immobilization. Besides GA, also divinylsulfone was used as linker molecule leading to a similar efficient immobilization for two enzymes, GibZea and NeoFis, whereas GA was superior in the other cases. Storage of the GA-immobilized enzymes for one month resulted in increased relative activities between 120 and 180%. The thermal stability was improved, especially for the GA-immobilized AspFum compared to the free enzyme after incubation for 4 h at 60 °C (10% vs. 235% residual activity). Especially after incubation of AspFum (free or immobilized) for 2 h at 50 °C a strongly increased activity was observed (up to 359% of the initial activity). This effect was studied in more detail, revealing that one heat activation prior and one after immobilization increased the overall immobilization efficiency. Recycling of the immobilized ATAs resulted only in a small reduction of activity after four batches. Asymmetric synthesis of (R)- or (S)-1-methyl-3-phenylpropylamine from the prostereogenic ketone using isopropylamine (IPA) as amino donor was applied with conversions up to 50% (AspFum) or 75% (3HMU). Except for NeoFis, all immobilized ATAs showed higher conversions compared to the free enzyme.
Journal: Journal of Biotechnology - Volume 191, 10 December 2014, Pages 32–37