During each day of harvest, wasted banana stems are obtained in large quantities. These stems are composed mainly of 74.37% cellulose which is a very important raw material. This study aims to isolate cellulose from banana stems using liquefaction, delignification and bleaching processes with a microwave  at power variations of 450, 600 and 800 W.  The results showed that the highest cellulose content of 86.43% was obtained at 800 W for 14 minutes. Meanwhile, the fourier-transform infrared spectroscopy (FTIR) analysis result did not show a peak at wavenumber 1519 cm-1 which is the specific peak for lignin but showed a peak for cellulose at wavenumber 898 cm-1. Furthermore, XRD analysis of crystallinity showed a typical diffraction peak of cellulose at 22.5o with a degree of crystallinity of 56.8% while, morphological analysis with SEM showed that the sizes of the cellulose fibers produced varied, ranging from 5 to hundreds of micrometers and visible fibrillary fibers

Silica gel (SG) is one of common adsorbent on solid phase extraction for preconcentration. Due to the low selectivity and effectiveness of adsorption to metal ions, SG should be modified. The SG was modified with d-glycine (Si-Gly) using 3-aminopropyltrimethoxysilane and glutaraldehyde as a crosslinker. Capability of Si-Gly as adsorbent for cadmium ions (Cd) was investigated using batch adsorption. The result was proved by infrared spectra. The optimum condition of Cd adsorption by the Si-Gly was obtained at pH 5, with 0.3 g of adsorbent and 11 minutes of contact time. The percentage of Cd adsorption at the optimum condition by the Si-Gly (99.34%) which is greater than the SG (89.03%). The maximum adsorption capacity of the Si-Gly is 9.77 mg/g, obtained at 400 mg/L. The Cd(II) adsorption on the SG and the Si-Gly follow the Langmuir isotherm equation.

Synthesis of glutaraldehyde cross-linked chitosan (chitosan-GA) has been done and characterized by using FTIR and TGA. Adsorption of Fe(III) ion by glutaraldehyde cross-linked chitosan (chitosan-GA) has been studied by using batch method. The objectives of this research are to know optimum adsorption condition of Fe(III) ion by chitosan-GA, then study influence of Cu(II) ion to adsorption of Fe(III) ion and its application to vetiver oil. Optimum conditions are finding out by response surface Box Behnken method. Percent adsorption value of Fe(III) ion by Chitosan-GA (DD = 78%) is about 91,8439% in optimum conditions : weight adsorbent 0,75 gram, temperature 25 o C, time contact 360 minutes. Percent adsorption of Fe(III) ion was decreased from 91,9521% to 79,724% because the existence of Cu(II) ion. The color of vetiver oil was changed from dark to reddish brown.

Most of the alcohol analytical methods are robust and instrumentally expensive. An alternative of ethanol biosensor based on selected biofilm forming Acetobacter aceti bacteria producing alcohol oxidase was constructed on a screen-printed carbon electrode. The enzyme specifically oxidizes the ethanol and generate electrical current that then electrochemically detected and measured by cyclic voltammetry method. A scanning electron microscopic analysis indicated that the biofilm was formed firmly in the electrode. This constructed biosensor reached its optimum at biofilm formed by bacteria of 1.33 × 1010 cells/ml, temperature of 27°C, and pH 7. The enzyme kinetic had KM and Vmax AOX values of 3.5 mm and 125 μA respectively. The biosensor had detection and quantization limit of 0.003 and 0.009%, respectively, and a sensitivity of 57.29 μA (%)-1. A linearity and relative deviation value were revealed at 0.993 and 1.95% respectively. The biosensor was relatively specific and had no interferences with methanol, sodium chloride and citric acid as the common interferences of ethanol compounds. Furthermore, the biosensor had been stably for at least 55 days. Therefore, this constructed biosensor should be developed into a prototype for a practical effective analysis.

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