Nur Rokhati

Immobilization of glucose oxidase on chitosan-based porous composite membranes and their potential use in biosensors

The glucose oxidase (GOx) enzyme was immobilized on chitosan-based porous composite membranes using a covalent bond between GOx and the chitosan membrane. The chitosan-based porous membranes were prepared by the combination of the evaporation- and non-solvent-induced phase separation methods. To increase the membrane conductivity, carbon nanotubes (CNTs) were added to the chitosan solution. The resulting membranes were characterized in terms of water permeability, surface morphology and surface chemistry. Enzyme immobilization was performed on the chitosan membranes with and without activation using glutaraldehyde (GA). Three different configurations of working electrodes were evaluated to investigate the potential use of the modified membranes in biosensors. The results show that enzyme immobilization capacity was greater for membranes that had been activated than for membranes that had not been activated. In addition, activation increased the stability of the enzyme immobilization. The immobilization of GOx on chitosan-based membranes was influenced by both pH and the concentration of the enzyme solution. The presence of CNTs significantly increased the electrical conductivity of the chitosan membranes. The evaluation of three different configurations of working electrodes suggested that the third configuration, which was composed of an electrode-mediator-(chitosan and carbon nanotube) structure and enzyme, is the best candidate for biosensor applications.

Performance Comparison of α- and β-Amylases on Chitosan Hydrolysis

The low solubility in common solvent and high viscosity resulting from its high molecular weight (MW) with fiber-like structure prevents a more widespread use of chitosan. This paper presents a performance comparison of nonspecific, commercially available enzymes, α- and β-amylases, for the hydrolysis of chitosan to lower its MW. The results showed that both enzymes demonstrate the ability to be used as catalysts in chitosan hydrolysis with β-amylase having better performance than α-amylase. The chitosan hydrolysis was influenced by not only the enzyme and the chitosan characteristics but also the hydrolysis condition. The optimum pH solution was 4 for α-amylase and 5 for β-amylase. The hydrolysis temperature was found to be optimal at 90 and 50°C for α- and β-amylases, respectively.

Polymeric Membrane Made of Cellulose Isolated from Tropical Water Hyacinth Blended with Chitosan

In Indonesia, membrane application is limited by the use of high cost imported membranes. Therefore, efforts to produce membrane using local materials are very important to be performed. Cellulose and chitosan are two materials, which their availability in Indonesia is abundant. In this work, cellulose acetate (CA) has been successfully produced from tropical water hyacinth via isolation and acetylation processes. By using FTIR, a comparative analysis of functional groups between the resulted CA and commercial CA was also investigated. The result shows that the IR spectra of the resulted CA and commercial CA are similar. The produced CA can further be processed into membrane. The resulting membranes were then characterized using SEM. In addition, the membranes were examined for filtering humic acid solution as surface water model. To improve the performance, CA membranes prepared from water hyacinth were modified by addition of chitosan (Chi) via blending in phase separation method. The resulting CA-Chi membranes were characterized using SEM and FTIR.

Production of Chitosan from Amusium sp Scallop Shell Waste

Chitosan is one of the natural polysaccharides, which is produced from chitin by deacetylation process. In this study, chitosan was produced from Amusium sp scallop shell waste. First, chitin was isolated by extraction via deproteinization using alkaline solution followed by demineralization using acid solution. Thereafter, chitosan was resulted from deacetylation of chitin using a high concentration of alkaline solution. The chemical structure of chitin and chitosan products was characterized using fourier transform infrared spectroscopy (FTIR).