Alginate-chitosan based biopolymer for possible application as edible film coating has been studied. Alginate hydrosol and chitosan hydrosol with mass ratio of 1:1 were mixed to form a thin membrane and then dried. The obtained alginate-chitosan membrane was confirmed using FTIR spectrophotometers. Characterization of the membrane, which includes thickness, tensile strength, water vapor sorption, resistance to pH change and antimicrobials properties, were conducted. It was showed that the interaction of alginate and chitosan in the membrane occurred through the electrostatic interaction of the carboxylic group of alginate and ammonium groups of chitosan. At the same thickness, the alginate-chitosan membrane tensile strength was higher and more resistant to pH changes than both native alginate and chitosan membranes. Furthermore, the alginate-chitosan membrane has good antibacterial potential against gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli). It is expected that the alginate-chitosan membrane has the potential application for safe and efficient fruit coating.
The synthesis of polyelectrolyte complexes (PEC) based on chitosan and determination of their antibacterial properties had been conducted. The microstructure of PECs obtained were described by SEM analysis, while inhibition activity of PECs against S. aureus and E. coli was determined by measuring inhibitory zone diameter. Characteristics of chitosan, alginate and κ-carrageenan as natural polymers which non-toxic, biodagradable and safe to eat meet the edible film criteria. Chitosan as a polycationic interacts with alginate and κ-carrageenan as polyanionic under the appropriate conditions to form PEC film. Based on FTIR spectra, it was found that interaction of chitosan and alginate as well as chitosan and κ-carrageenan was an electrostatic interaction. Microstructure study using SEM found that PECs have irregular and fibrous surface structure. Based on their inhibitory activity against S. aureus and E. coli, PECs have the strongest antibacterial activity compared to their original polymer. Therefore, PECs film could be excellent edible film for food coating that protect product from bacterial contamination.
The preparation of polyelectrolyte complex (PEC) based on bio-composite materials often requires crosslinking agents to achieve the desired stability and properties of the material formed. PEC with opposite charges has the advantage in self-crosslinking through electrostatic interactions. Chitosan is a positively charged polysaccharide with -NH3
+ group while κappa-carrageenan is a negatively charged polysaccharide with -OSO3
− group. This work focused on synthesizing chitosan-carrageenan membrane and determining its characteristics. The membrane was prepared by interacting chitosan and carrageenan hydrosols at a pH of 5. The obtained chitosan-carrageenan membrane had better physical-mechanical properties, including tensile strength (load), elongation (strain), and elasticity (modulus young), adsorption, and resistance of water, than the constituent polymers. The FTIR spectra indicated the presence of self interaction in membrane between protonated amine groups of chitosan and sulfate groups of carrageenan. The difference in surface morphology among chitosan-carrageenan membrane and its constituent membranes was confirmed by SEM analysis.
A screen-printed three-electrode system is fabricated to prepare a novel screen-printed biosensor for rapid determination of Hg(II) in aqueous solution. The amperometric biosensor is prepared by entrapping urease in alginate–chitosan membrane to modify the screen-printed carbon electrode. The urease/alginate–chitosan membrane for Hg(II) had optimum measurement conditions at work potential of -0.15 V, pH of 7, urea concentration of 75 mM, response time of 8 seconds, inhibition time of 7 minutes and temperature of 25 °C. The resulted biosensor characteristic were found to have the range concentration of Hg(II) ion between 40-90 ppb with the detection limit I10% was 66.45 ppb, the coefficient of variance (Cv) was 0.8%, and reactivation was 5 times reuse.
Determination of glucose concentration in urine and blood that anyone can use at any time is Benedict reagent based chemical sensor. This optical sensor was developed by immobilizing Benedict reagent into nata cellulose as supporting material via entrapment. The nata cellulose/Benedict membrane for glucose determination has optimum condition at maximum wavelenght of 541.57 nm, Benedict concentration of 0.4470 M, and ratio of nata cellulse mass to Benedict volume was 1:3. Characterization of optical sensor for glucose was in working range of 0-5000 ppm, limit of detection was 911,11 ppm, sensitivity was 0.0009 and reproducibility was 0.2295%.
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