Telah dipelajari peranan kation logam dalam imobilisasi papain pada kitosan. Kitosan dibuat melalui deproteinasi, demineralisasi diikuti deasetilasi kitin dari cangkang udang windu (Penaus monodon). Pada penelitian ini peranan kation logam Mg(II), Ca(II), Cu(II) dan Zn(II) terhadap proses imobilisasi papain dievaluasi, meliputi sifat adsorpsi, gugus fungsional, ukuran pori dan perubahan aktivitas proteolitik papain terimobilisasi. Penelitian ini diawali dengan identifikasi secara spektroskopi inframerah terhadap gugus fungsional kitosan yang diperkirakan berfungsi sebagai situs aktif imobilisasi. Beberapa parameter yang diinvestigasi pada peneltian ini, antara lain pH medium, laju adsorpsi dan imobilisasi (k1), energi (E) dan kapasitas adsorpsi dan imobilisasi (b). Model kinetika adsorpsi orde satu dan pseudo orde 2 digunakan sebagai dasar untuk mengestimasi laju adsorpsi dan imobilisasi, sedangkan model isoterm adsorpsi Langmuir digunakan untuk menetapkan energi dan kapasitas adsorpsi dan imobilisasi. Peranan kation logam pada imobilisasi papain diinvestigasi dengan cara mempelajari perubahan aktivitas proteolitik papain terimobilisasi. Hasil penelitian menunjukkan bahwa kitosan bead mempunyai ukuran pori lebih besar dibanding kitosan serbuk sehingga kitosan bead lebih sesuai untuk matriks imobilisasi papain. Hasil identifikasi gugus fungsional, sifat adsorpsi (kapasitas , laju dan energi) logam, perubahan aktivitas proteolitik papain terimobilisasi menunjukkan bahwa imobilisasi papain pada kitosan melibatkan gugus fungsional NH2. Energi adsorpsi ion logam Mg(II), Ca(II), Cu(II) dan Zn(II) dari 21,04 sampai 28,57 kJ/mol sedangkan energi imobilisasi 31,43 sampai 33,13 kJ/mol. Kapasitas adsorpsi kation logam Mg(II), Ca(II), Cu(II) dan Zn(II) pada kitosan bead secara signifikan lebih besar dibanding kapasitas imobilisasi papain pada matriks kitosan bead-logam. Kapasitas adsorpsi kation logam Mg(II), Ca(II), Zn(II) dan Cu(II) pada kitosan bead adalah 17,39.10-4 mol/g; 19,61. 10-4 mol/g , 20,02. 10-4 mol/g dan 23,15. 10-4 mol/g sedangkan kapasitas imobilisasi papain pada kitosan bead-Mg(II) kitosan bead-Ca(II), kitosan bead-Zn(II) dan kitosan bead- Cu(II) adalah 46,61. 10-6 mol/g; 67,98.10-6 mol/g; 79,84.10-6 mol/g; dan 93,27.10-6 mol/g. Laju imobilisasi papain pada kitosan bead-Mg(II), kitosan bead-Ca(II), kitosan bead- Zn(II) dan kitosan bead-Cu(II) adalah 8.26.10-4 menit-1; 9.38 10-4 menit-1, 11.20 .10-4 menit-1 and 16.08 .10-4 menit-1 . pH optimum proses imobilisasi papain pada matriks kitosan bead-kation logam tercapai pada kisaran pH dari 7 sampai 8. Papain terimobilisasi mempunyai suhu optimum yang lebih tinggi dibanding papain bebas. Papain terimobilisasi mampu digunakan ulang sebanyak 10-12 kali dengan aktivitas masih sekitar 7- 10 % pada pemakaian yang ke-12.

The involvement of metal cation in papain immobilization on chitosan was studied. The chitosan was made by deproteination, demineralization followed by deacetylation of chitin from shrimp shell (Penaus monodon). In this studies, the involvement of metal cation Mg(II), Ca(II), Cu(II) and Zn(II) in papain immobilization was evaluated i.e properties of adsorption, functional group, size of pore, and the change of proteolitytic activities in the immobile papain.. This work was started with the Infra Red Spectroscopy identification of functional groups which is expected to be the adsorption and immobilization active sites. Parameters investigated in this work such as medium pH, adsorption and immobilization rate (k1), energies (E) and capacity of adsorption and immobilization (b). The kinetic model of first order adsorption and pseudo second order was applied to estimate the adsorption and immobilization rate, whereas the isotherm adsorption Langmuir model was employed in the determination of the energy and the capacity in adsorption and immobilization. The involvement of metal cations were investigated by studying the change of the proteolytic activities in the papain immobile compared with that in the native papain. The results showed that the chitosan bead possesses bigger pore size than chitosan powder, so that chitosan bead should be more compatible as matrix in the immobilization of papain. The result of identification of functional groups, the properties of adsorption (capacity and rate of adsorption) of metals, the change of proteolitic activities in the immobile papain expected to be involved in the adsorption and the immobilization was NH2. The energies of adsorption of Mg(II), Ca(II), Cu(II) and Zn(II) metal ions on chitosan were ranging from 21.04 to 28.57 kJ/mole, whereas the energies of papain immobilization were from 31.43 to 33.13 kJ/mole. The adsorption capacity of Mg(II), Ca(II), Cu(II) and Zn(II) metal ions on chitosan bead were significantly bigger than that the immobilization of papain on chitosan bead- metal. The adsorption capacity of metal cation on chitosan bead Mg(II), Ca(II), Zn(II) and Cu(II) were 17.39.10-4 mol/g; 19.61. 10-4 mole/g , 20.02. 10-4 mole/g and 23.15. 10-4 mole/g respectively. Whereas the capacity of immobilization papain on chitosan bead-Mg(II), chitosan bead-Ca(II), chitosan bead-Zn(II) and chitosan bead-Cu(II) were 46.61. 10-6 mole/g; 67.98.10-6 mole/g; 79.84.10-6 mole/g; and 93.27.10-6 mole/g. The rate of immobilization papain on chitosan bead-Mg(II), chitosan bead-Ca(II), chitosan bead- Zn(II) and chitosan bead- Cu(II) were 8.26.10-4 min-1; 9.38 . 10-4 min-1, 11.20 .10-4 min-1 and 16.08 .10-4 min-1 respectively. The optimum pH of immobilization process on chitosan bead- metal cation matrix was ranging from 7 to 8. The thermal stability of the immobilized papain, relative to that of the native papain, increased markedly. The immobilized papain can be reused for at least 10 to 12 times and still had activity around 7-10 % on the 12th using.

Kata Kunci : Data imobilisasi,Imobilisasi papain,Kation logam,Kitosan