The fusions of elastin-like polypeptides and xylanase self-assembled into insoluble active xylanase particles.

We fused the genes of elastin-like polypeptides (ELPs) and xylanase and then expressed them in Escherichia coli. Unexpectedly, the fusion proteins self-assembled into insoluble active particles as the ELPs underwent a hardly reversible phase transition. The specific activity of the particles was 92% of the native counterparts, which means it can act as a pull-down handler for converting soluble proteins into active aggregates. We evaluated the characterizations of the insoluble active xylanase particles in detail and the results were encouraging. The pH optimum (6.0) of the particles was the same as the free one, but the optimum pH range was 5-7, while the free xylanase was 6-7. The free xylanase had an optimum temperature of 50°C, whereas the insoluble active xylanase particles shifted to 70°C. The pH stability, thermostability and storage stability of the xylanase particles increased significantly when compared with the free xylanase. We also observed an increase of the Km values of the free xylanase from 0.374gL(-1) to 0.980gL(-1) at the insoluble state. The considerable higher activity and stability of the xylanase particles were much like immobilized xylanases and could be valuable for its industrial application.