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The potential applications of alginate lyase in pharmaceutical, food, agriculture, bioenergy and medical diagnostic industries and the high cost of commercially available alginate lyase necessitate searching for microbial biocatalyst for sustainable and economical production of this enzyme. In the current study, a potent alginate lyase-producing bacterium was isolated from decomposed Sargassum seaweed waste off Barbados' coast and identified as Arthrobacter sp. AD-10 (GenBank accession number MG983495) via 16S rRNA gene sequencing. Biocatalytic efficacy of this novel bacterium for cleaving alginate was assessed by immobilizing its extracted alginate lyase onto functionalized chitosan nanoparticles. Glutaraldehyde cross-linked chitosan nanoparticles could able to retain 79.3% of alginate lyase activity. Chitosan-nanoparticle immobilized alginate lyase exhibited pH and temperature optimum at pH 8 and 45 °C, respectively, and had a strong affinity toward alginate by displaying a low K m (1.21 mg/mL) and a high V max (11.3 U/mg-protein) value. Activation energy, enthalpy and entropy of catalysis values were recorded as 42.2 kJ/mol, 39.7 kJ/mol and −105.2 J/mol/K, respectively. Additionally, the immobilized alginate lyase was not affected by 0.34 M NaCl and retained 66.3% of its maximal activity after seven consecutive reuses. These promising biocatalytic characteristics suggest the industrial potential of chitosan-nanoparticle immobilized alginate lyase for bioprocessing of alginate. [ABSTRACT FROM AUTHOR]