The Research Of Glucose Non-enzyme Detection System During Fermentation

Glucose,the carbon source and the reactive substance required for bacterial growth during the fermentation process,is directly determine the quality and yield of the produced product.Different fermentation stages have different requirements for the glucose concentration.So it is extremely important for real-time on-line detection of glucose concentration.The glucose biosensor of the existing glucose detection devices mostly use glucose oxidase(GOx)as its core detection elements.The glucose biosensor can be divided into two types of detection methods,which is the enzyme membrane type and the enzyme liquid type.The glucose biosensor,use enzyme as the molecular recognition element,is affected by the characteristics of the biological macromolecules of enzyme.Its stability is highly dependent on the detection environment.And it has a short operating life,which ofthen needs to be replaced.The Enzyme membrane sensors require high cost of carrier and reagents for immobilization.And the complex preparation process also lead to the attenuation of enzyme activity and poor repeatability.The enzyme-liquid sensors have long detection time and low sensitivity.And the enzyme solution needs to be re-added during each detection process,which leads to the waste of the enzyme solution and increased cost.At the same time,the transmission of the enzyme solution can easily block the pipeline.In the previous research,we have developed an enzyme-liquid on-line glucose analyzer.The analyzer is mets the requirements for glucose detection in the fermentation process,but it has large actual error.Therefore,it is important to develop a glucose biosensor with good performance,which contains short detection time and low noise.Enzyme-free glucose sensors use nano-materials,such as metals and their oxides,as detection elements.The detection principle of non-enzyme sensors is the glucose further oxidize by electrocatalyze on the surface of the nano-electrodes to generate the current response,which have linear relationship with the glucose concentration.The enzyme-free glucose sensor is not easily affected by the environment.Simultaneously,its not affected by the partial pressure of oxygen in the solution,which because of the detection principle of enzyme-free glucose sensor is different of the enzyme sensor.Also,it has low working voltage and short detection time.However,the enzyme-free glucose sensor has low selectivity and poor anti-toxicity,which is due to the adsorption of Cl-and intermediate product on the surface of electrode.The stability of non-enzyme glucose sensor is severely affected.Therefore,the key to solve the problems the problems faced by enzyme-free glucose sensors in the field of glucose detection during fermentation is design a new enzyme-free glucose sensor with long-term stability,good selectivity and anti-toxicity.In order to solve the problem of glucose detection in the fermentation process,An@Ni/C enzyme-free glucose sensor with excellent performance was proposed.At the same time,the software and hardware for glucose detection based on the enzyme-free glucose sensor were designed and implemented.Based on those,the mechanism model of sensor performance loss compensation after long-term operation of the enzyme-free glucose sensor was studied.The main research results obtained are as follows:(1)Design and prepare Au@Ni/C enzyme-free glucose sensorBased on the Au-based sensor,an glucose-free sensor with a core-shell structure is designed.The core-shell structure makes the operating voltage of sensor negatively shift and solves the problem that the bare Au electrode is susceptible to chloride ion and impurities.So,the sensor has good selectivity and anti-toxicity.And the stability and detection time are greatly improved compared with the existing enzyme sensors.The linear range for the detection of glucose is from 0.5 mmol L^-1to 10 mmol L^-1with a rapid response time of ca.3 s,sensitivity estimated to be 92.68mA cm^-2mM^-1,and a detection limit of 0.0157 mM.The Au@Ni/C enzyme-free glucose sensor designed in this paper can be used in the field of glucose detection during fermentation.(2)Research and establish loss compensation model of enzyme-free glucose sensorEstablished the loss compensation mechanism model of enzyme-free glucose sensor.The model is based on Burke's"Incipient Hydrous Oxide Adatom Mediator theory"and Ostwald Ripening theory.The model illustrates that the enzyme-free glucose sensor after long-term operation have the decrease of the current response to the same glucose concentration is due to the surface interface energy of nanoparticles with different particle sizes lead to the appearance of concentration gradient.Accordingly,the overall specific surface area of the sensor decreases,which causes the current response to linearly decay with the specific surface area.The verification experiment was designed to verify the accuracy of the model.The diffusion coefficient of the Au@Ni/C non-enzyme glucose sensor is estimated by the experimental data on 0.5 day.Then,the particle size distribution at 0.5-7 days is predict and calculate the specific surface area attenuation rate.The results show that the current response decay curve predicted by the mechanism model is highly consistent with the current response curve of the three Au@Ni/C enzymeless glucose sensors tested,which proves that the accuracy of the established enzymeless glucose sensor loss compensation model meets the requirements.(3)Designed and implemented the software and hardware of glucose-free enzyme detection systemIn order to achieve the function of the detection system,which contains constant potential control of the three-electrode detection system,weak signal conditioning of the enzyme-free glucose sensor,collection of detection data,transmission and display of the host computer and OLED and the system power,the lower computer software system and external hardware circuit based on STM32F103C8T6 is designed and implemented.The hardware mainly includes STM32 data acquisition circuit,three-electrode constant voltage detection circuit,micro-current detection circuit,output and display interface and power supply circuit.The glucose detection system has two working modes of constant potential and cyclic voltammetry.The controllable range of the three-electrode voltage is-2.5-2.5 V,the current response resolution is 0.05mA,and the measurable current range is-1.5-1.5 mA.The above characteristics fully meet the detection needs of Au@Ni/C non-enzyme glucose sensors and other non-enzyme glucose sensors.