Synthesis of biocontrol macromolecules by derivative of chitosan with surfactin and antifungal evaluation.

A derivative of chitosan was prepared with chitosan and β-cyclodextrins, which was synthesized by the immobilization reaction, as a carrier to adsorb surfactin produced from Bacillus amyloliquefaciens and got biological macromolecules. The antifungal activity against three sapstain fungi by a combination of macromolecules was tested. The results showed that the macromolecules inhibited the mycelium growth of sapstain fungi Lasiodiplodia rubropurpurea, L. crassispora, and L. theobromae by about 73.22%, 76.72%, and 70.22%, respectively. The macromolecules were relatively thermally stable with more than 50% of the antifungal activity even after being held at 121°C for 30 min. Meanwhile, the activity of the macromolecules remained more than 55% at a pH value ranging from 4 to 12. The macromolecules were resistant to hydrolysis by most protein-denaturing detergents and other enzymes. The results indicated the macromolecules might provide an alternative bioresource for the bio-control of sapstain.