This study aimed to identify chitosan polymers that have antibacterial activity against the bacterial wilt pathogen. The chitosan polymers were enzymatically synthesized using chitosan and five cinnamic acids (CADs): caffeic acid (CA), ferulic acid (FA), cinnamic acid (CIA), p -coumaric acid (COA) and chlorogenic acid (CHA), using laccase from Pleurotus ostreatus as a catalyst. The reaction was performed in a phosphate buffered solution under heterogenous reaction conditions. The chitosan derivatives (CTS- g -CADs) were characterized by FT-IR, XRD, TGA and SEM. FT-IR demonstrated that the reaction products bound covalently to the free amino groups or hydroxyl groups of chitosan via band of amide I or ester band. XRD showed a reduced packing density for grafted chitosan comparing to original chitosan. TGA demonstrated that CTS- g -CADs have a higher thermostability than chitosan. Additionally, chitosan and its derivatives showed similar antibacterial activity. However, the IC 50 value of the chitosan-caffeic acid derivative (CTS- g -CA) against the mulberry bacterial wilt pathogen RS-5 was 0.23 mg/mL, which was two-fifths of the IC 50 value of chitosan. Therefore, the enzymatically synthesized chitosan polymers can be used to control plant diseases in biotechnological domains. [ABSTRACT FROM AUTHOR]