Evaluation of multi-walled carbon nanotubes bearing aldehyde groups of different lengths for the immobilization of Geobacillus kaustophilus L-asparaginase

Abstract

In this study, l-asparaginase from Geobacillus kaustophilus was recombinantly expressed in E. coli and purified using Ni2+-NTA column. The purified l-asparaginase was then immobilized covalently on multi-walled carbon nanotubes containing an aldehyde group with different spacer arms to mitigate acrylamide from potato chips. All the free and immobilized l-asparaginase preparations had an optimum pH at 8.5. The optimum temperature 55 C-degrees for free l-asparaginase, whereas the optimum temperature was 65 C-degrees for all immobilized preparations. The thermal stability of immobilized l-asparaginases was at least 17- and 32-fold higher than that of the free enzyme at 55 and 65 C-degrees, respectively. All immobilized l-asparaginases retained 90 % of their initial activity after 20 reuses. In potato chips, the acrylamide mitigation was achieved as 93 % for free l-asparaginase and >95 % for immobilized l-asparaginases after a reaction time of 60 min. The results show that the immobilized preparations of G. kaustophilusl-asparaginase are robust and more efficient biocatalysts than their free counterparts in the mitigation of acrylamide from potato chips.