Sucrose is a type of sugar that is widely used in various types of foods and beverages. In Indonesia, sucrose consumption reaches 2.8 million tons on average per year. Effects of consuming too much sucrose can increase the risk of various diseases such as diabetes, dental caries and obesity. The level of maximum amount of sucrose that is safe for the body equal to 10% of the total energy or the equivalent of 50 g/person/day, so that the required detection system and the identification of the sucrose concentration. In this work, the identification process was carried out using an amperometric biosensor based on the yeast Saccharomyces cerevisiae as a bioreceptor. Measurements were made by immobilizing yeast cells and analyte samples into the biosensor electrodes and observed based on cellular respiration activity which was expressed as a parameter of dissolved oxygen (DO). The biosensor response is generated in the form of an output potential value, then processed using principal component analysis (PCA) to produce a sucrose concentration classification point with a percentage of variance of the two main components of 98.77% which states that the sensor is able to identify sucrose concentrations.
Environmental problems including water and air pollution, over fertilization, insufficient wastewater treatment and even ecological disaster are receiving greater attention in the technical and scientific area. In this paper, a method for water quality monitoring using living green algae (Chlorella Kessleri) with the help of the intelligent mobile lab (IMOLA) is presented. This measurement used two IMOLA systems for measurement and reference simultaneously to verify changes due to pollution inside the measurement system. The IMOLA includes light emitting diodes to stimulate photosynthesis of the living algae immobilized on a biochip containing a dissolved oxygen microsensor. A fluid system is used to transport algae culture medium in a stop and go mode; 600s ON, 300s OFF, while the oxygen concentration of the water probe is measured. When the pump stops, the increase in dissolved oxygen concentration due to photosynthesis is detected. In case of a pollutant being transported toward the algae, this can be detected by monitoring the photosynthetic activity. Monitoring pollution is shown by adding emulsion of 0,5mL of Indonesian crude palm oil and 10mL algae medium to the water probe in the biosensor.
A biosensor system for dissolved oxygen level detection based on a current mirror method has been designed and characterized. Most biosensor systems implement a transimpedance circuit to convert the flowing current on the sensor to an output voltage signal. These systems are voracious and susceptible to instability and noise due to the configuration of the circuit used. The power supply is also impractical due to the bipolar polarity needed, and the systems consume more power since they use more active devices in the op-amp. These disadvantages need to be overcome when special requirements are needed such as low-noise measurement in dissolved oxygen level detection, and for battery-powered and low-power devices for in situ and remote area measurement. Differing from transimpedance, current mirror circuits convert the flowing current to the output voltage by copying the current with a ground-referenced input and output, and use fewer active devices. The proposed current mirror circuit aims to diminish the noise of the output and minimize the power consumption through reducing the active devices used. The results show some significant signal quality improvements when using the current mirror circuit, where the noise response of the current mirror circuit is ten times lower than the transimpedance circuit.
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