Characterization and antimicrobial activity of water-soluble N-(4-carboxybutyroyl) chitosans against some plant pathogenic bacteria and fungi

► Water-soluble N-(4-carboxybutyroyl) chitosan derivatives with different degrees of substitution (DS) were synthesized to enhance the antimicrobial activity of chitosan molecule against plant pathogens. ► The chemical structures were characterized by 1H and 13C NMR spectroscopy and the data showed that the acylate reaction took place at the N-position of chitosan. ► The derivatives exhibited a wide range of antimicrobial activity against bacteria of crown gall Agrobacterium tumefaciens and soft mold Erwinia carotovora and fungi of grey mold Botrytis cinerea, damping off Pythium debaryanum and Rhizoctonia solani. ► It was found that the attachment of the carboxybutyroyl moiety on the amino group of chitosan is not necessarily sufficient to obtain high antimicrobial action. The key issue is the optimal DS in relation to the polymer backbone.