Enzyme immobilizations were widely used to increase their shelf life which is essential for the world’s industries. Therefore, amylase immobilized using Na-alginate as a matrix is necessary optimized and characterized. The parameters measured in the optimization of immobilization are the determination of the concentration of sodium alginate and contact time. Characterizations were conducted to determine the optimum concentration of substrate, the value Vmax, Michaelis-Menten constant (KM), pH, temperature, incubation time, and test reuse. The process of immobilized amylase activity test was performed in a continuous flow system using a reactor, and its sugar levels were determined using the Dinitro Salisilat Method (DNS). The results reveal that the immobilized amylase commercial has optimum concentration of Na-alginate of 5% (w/v) and contact time of 90 minutes with an immobilization efficiency value of 43.02%. Furthermore, the immobilized amylase has optimum activity at substrate concentrations of 3.5% (w/v), pH 4, incubation temperature of 40 °C, and a reaction time of 20 minutes with the value of the activity of 2760.4 U / mL. KM value of free amylase and immobilized amylase row are 0.18 mM and 0.15 mM, repectively. The value of KM immobilized amylase is smaller than the free enzyme. It proves that the immobilized amylase has a high affinity for the substrate. The immobilized amylase can be used up to 12 times with a value of the residual activity of 56.7%.

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A bacterial lipase producer was isolated from garbage dump soil and was identified its genus. Lipase was extracted according to production time optimized, purified using ammonium sulfate fractionation and gel chromatograph. Determination of enzyme characteristic studied were influence of pH, temperature, various metals to lipase activity. The result of this research shows that the genus of isolated bacteria which produced lipase was Acinetobacter sp., the lipase optimum production time is about 18 hours with the activity is about 115 unit/mL. The highest activity of lipase fractionation using ammonium sulfate is about 45% and the highest activity of purifying with filtration gel chromatograph column using Sephadex G-150 at 24 th fraction. Lipase from crude extract and purifying product at this fraction has optimum pH 6 and optimum temperature is about 40 o C. Lipase to be classified as metalloenzyme that shows with decreasing the activity after added the EDTA. Metals ion, such as Cu 2+ and Zn 2+ were inhibited the lipase activity. Ca 2+ ion could increase lipase crude extract activity but inhibited the activity of lipase purifying product. Hg 2+ ion could increase the activity of lipase purifying product.

Glucose biosensors based on porous material of alginate cryogel has been developed, and the cryogel provides a large surface area for enzyme immobilization. The alginate cryogel has been supplemented with NiFe2O4 nanoparticles to improve the electron transfer for electrochemical detection. The fabrication parameters and operational conditions for the biosensor have also been optimized. The results showed that the optimum addition of NiFe2O4 nanoparticles to the alginate solution was 0.03 g/mL. The optimum operational conditions for the electrochemical detection were a cyclic voltammetry scan rate of 0.11 V/s, buffer pH of 7.0, and buffer concentration of 150 mM. The fabricated alginate NiFe2O4 nanoparticles cryogel-based glucose biosensor showed a linear response for glucose determination with a regression line of y = 18.18x + 455.28 and R² = 0.98. Furthermore, the calculated detection limit was 0.32 mM and the limit of quantification was 1.06 mM.

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