Immobilisation of the Thermostable l -aminoacylase from Thermococcus litoralis to Generate a Reusable Industrial Biocatalyst

A thermostable archaeal l -aminoacylase from Thermococcus litoralis has been used in immobilisation trials to optimise its application in industrial biotransformation reactions. Immobilisation techniques used included direct adsorption and crosslinking of the enzyme onto solid supports, bioencapsulation, and covalent bonding onto a variety of activated matrices. The most successful immobilisation methods were covalent binding of the enzyme onto glyoxyl-Sepharose and Amberlite XAD7. These methods yielded an average of 15 and 80 mg of protein bound per gram of support (wet weight for glyoxyl-Sepharose), respectively, with nearly 80% activity recovery in both cases. Enzyme immobilised onto glyoxyl-agarose was stabilised 106-fold under aqueous conditions and 142-fold in 100% acetonitrile when activity was measured after 24 h at 90°C. A column bioreactor containing the recombinant l -aminoacylase immobilised onto Sepharose beads was constructed with the substrate, N -acetyl- dl -Trp, continuously flowing at 60°C for 10 days. No loss of activity was detected over five days, with 32% activity remaining after 40 days at 60°C. These results show the potential of the use of immobilised l -aminoacylase in biotransformation reactions for the production of fine chemicals.