Efficiency of Immobilized Enzymes on Bacterial Magnetosomes

Despite the advancements of enzyme immobilization, improved immobilization techniques and new sources of supporting material is still a necessity. In this work, we have immobilised different enzymes such as alpha-amylase, alpha-glucosidase, lipase and catalase onto bacterial magnetosomes extracted from magnetotactic bacteria (MTB). Among the four enzymes, catalase and lipase showed significant increase in enzyme activity whereas the other two showed reduced activity when compared to the free enzyme. The free catalase activity was found to be 300.9 U/mg whereas the immobilised catalase activity was found to be 534.0 U/mg. The enzyme activity after immobilisation increased by 33.5% when compared to free enzyme. The spectrophotometric studies on the lipase activity with p-nitrophenyl acetate as substrate showed 2-5% increase in the activity for the immobilised lipase over free enzyme. However, the activity of magnetosome immobilised alpha-glucosidase and alpha-amylase decreased by 6 and 20%, respectively, compared to free enzyme. The decline in activity might be due to the insufficient coupling of enzymes with magnetosomes and leaching of unbound enzymes while washing. The results indicate that the process of coupling the magnetosomes with the enzymes needs to be improved for attaining enhanced activity.