ABSTRAKBiopolimer kitosan memiliki banyak aplikasi diantaranya sebagai biosorben, scaffold, bahan pengawet ikan, dan anti mikroba pada makanan. Dalam beberapa penelitian, kitosan sangat efektif dalam mengadsorpsi ion zat warna Metilen biru. Adapun tujuan dari penelitian ini untuk identifikasi karakteristik kitosan hasil isolasi dari cangkang kerang Mutiara. Proses isolasi biopolimer kitosan menggunakan metode deasetilasi bertahap. Dimana proses isolasi dilakukan dengan tiga proses yaitu deproteinasi, demineralisasi, dan deasetilasi. Serbuk hasil isolasi diidentifikasi rendemennya, diukur densitasnya, analisis gugus fungsi yang terbentuk dengan FTIR, dan menghitung kemampuan dalam mengadsorbsi zat warna metilen blue dengan Uv-Vis. Hasil penelitian menunjukkan bahwa kitosan yang dihasilkan berbentuk serbuk berwarna putih keabuan, rendemen 33,71%, densitas curah kitosan sebesar 1,21 gr/, serta didapat derajat deasetilasi dari kitosan sebesar 57,50 %. Efisiensi penyerapan zat warna Metilen biru oleh kitosan di setiap konsentrasi rata-rata bernilai 90 %. Oleh karena itu, biopolimer kitosansangat efektif dalam mengadsorbsi zat warna metilen blue. Kata kunci: deasetilasi bertahap; efisiensi penyerapan; karakteristik kitosan. ABSTRACTChitosan biopolymer has many applications including as a biosorbent, scaffold, fish preservative, and antimicrobial in food. In several studies, chitosan was very effective in adsorption of methylene blue dye ions. The purpose of this study was to identify the characteristics of chitosan isolated from pearl shells. The process of isolation of chitosan biopolymer uses the stepwise deacetylation method. Where the isolation process is carried out by three processes, namely deproteination, demineralization, and deacetylation. The isolated powder was identified its yield, measured its density, analyzed the functional groups formed by FTIR, and calculated the ability to adsorb methylene blue dye with UV-Vis. The results show that the chitosan is a grayish-white powder, the yield is 33.71%, the bulk density of chitosan is 1.21 gr/cm3, and the degree of deacetylation of chitosan is 57.50%. The absorption efficiency of methylene blue dye by chitosan at each concentration averaged 90%. Therefore, chitosan biopolymer is very effective in adsorbing methylene blue dye. Keywords: gradual deacetylation; absorption efficiency; chitosan characteristics.