Glucose monitoring biosensor
Image 12
A good example of a biosensor in frequent use is the glucose oxidase enzyme. The enzyme is immobilized on an electrode surface which acts as an electrocatalyst for oxidation of glucose. The biosensor gives reproducible electrical signal for glucose concentrations as low as 0.15 mM.
(Image ref 12- http://www.pinnaclet.com/glucose.html)
(Image ref 12- http://www.pinnaclet.com/glucose.html)
biosensor for cell population
Lactate Sensor
A lactate sensor composed of lactate oxidase and a voltammetric device to determine hydrogen peroxide is used to determine the numbers of lactate acid produced in the bacteria. The system consists of a lactate sensor in a membrane filter for trapping lactic acid producing bacteria.
The principle of the system for the determination of cell numbers ia as follows: Lactic acid producing bateria produce mainly lactate as a metabolite from glucose. The rate of lactate production depends on the cell numbers retained on the membrane filter, when the glucose concentration of the sample solution is constant. Therefore, the current obtained from the lactate sensor is also affected by the cell number on the membrane filter. The system is suitable for the specific determination of lactic acid producing bacteria.
A lactate sensor composed of lactate oxidase and a voltammetric device to determine hydrogen peroxide is used to determine the numbers of lactate acid produced in the bacteria. The system consists of a lactate sensor in a membrane filter for trapping lactic acid producing bacteria.
The principle of the system for the determination of cell numbers ia as follows: Lactic acid producing bateria produce mainly lactate as a metabolite from glucose. The rate of lactate production depends on the cell numbers retained on the membrane filter, when the glucose concentration of the sample solution is constant. Therefore, the current obtained from the lactate sensor is also affected by the cell number on the membrane filter. The system is suitable for the specific determination of lactic acid producing bacteria.
biosensors for products
Alcohol Sensor
Continual measurements of ethyl alcohol concentration in culture broth are required for fermentation industries. Furthermore, in the cultivation of yeasts using sugar as a carbon source it is well known that ethyl alcohol as a bi-product decreases the sugar basis yield of whole cells. In the cultivation of micro-organisms using methyl alcohol as a carbon source, the concentration of methyl alcohol must be maintained at the optimum level to avoid substrate inhibition.
It is well known that many micro-organisms utilize alcohols as carbon sources. Assimilation of alcohols by micro-organism can be determined from the respiration activity of micro-organisms. The respiration activity is directly measured with an oxygen electrode. Therefore, it is possible to construct a microbial sensor for alcohols using immobilized micro-organisms and a oxygen electrode. A microbial electrode consisting of immobilized yeasts or bacteria, a gas permeable teflon membrane and an oxygen electrode can be prepared for the determination of methyl and ethyl alcohol. Furthermore, the microbial sensor can be applied to continuous determination of alcohols in a fermentation broth.
Continual measurements of ethyl alcohol concentration in culture broth are required for fermentation industries. Furthermore, in the cultivation of yeasts using sugar as a carbon source it is well known that ethyl alcohol as a bi-product decreases the sugar basis yield of whole cells. In the cultivation of micro-organisms using methyl alcohol as a carbon source, the concentration of methyl alcohol must be maintained at the optimum level to avoid substrate inhibition.
It is well known that many micro-organisms utilize alcohols as carbon sources. Assimilation of alcohols by micro-organism can be determined from the respiration activity of micro-organisms. The respiration activity is directly measured with an oxygen electrode. Therefore, it is possible to construct a microbial sensor for alcohols using immobilized micro-organisms and a oxygen electrode. A microbial electrode consisting of immobilized yeasts or bacteria, a gas permeable teflon membrane and an oxygen electrode can be prepared for the determination of methyl and ethyl alcohol. Furthermore, the microbial sensor can be applied to continuous determination of alcohols in a fermentation broth.
Some of the important biosensors used in environmental pollution monitoring are:
a) Gas biosensors- In order to detect gases such as sulphur dioxide, (SO2), methane, carbon dioxide etc, microbial biosensors have been developed.Thiobacillus-based biosensors can detect the pollutant SO2, whereas methane (CH4) can be detected by immobilized Methalomonas. A particular strain ofPseudomonas is used to monitor carbon dioxide levels.
b) Immunoassay biosensors- Immunoelectrodes as biosensors are used to detect low concentrations of pollutants. Pesticide specific antibodies can detect the presence of low concentrations of triazines, malathion and carbamates, by using immunoassay methods.
c) BOD biosensor- Biological oxygen demand (BOD) is widely used as a test to detect the levels of organic pollution. This requires five days of incubation but a BOD biosensor using the yeast Trichosporon cutaneum with oxygen probe takes only 15 minutes to detect organic pollution.
d) Miscellaneous biosensors- A graphite electrode with Cynobacterium andSynechococcus has been developed to measure the degree of electron transport inhibition during the photosynthesis due to certain pollutants e.g. herbicides. To detect phenol, phenol oxidase enzyme obtained from potatoes and mushrooms is used as a biosensor. Biosensors for the detection of polychlorinated biphenyls (PCBs) and chlorinated hydrocarbons and certain other organic compounds have also been developed. Biosensors employing acetylcholine esterase which can be obtained from bovine RBC can be used for the detection of organophosphorus compounds in water.
(Ref. no 1)
b) Immunoassay biosensors- Immunoelectrodes as biosensors are used to detect low concentrations of pollutants. Pesticide specific antibodies can detect the presence of low concentrations of triazines, malathion and carbamates, by using immunoassay methods.
c) BOD biosensor- Biological oxygen demand (BOD) is widely used as a test to detect the levels of organic pollution. This requires five days of incubation but a BOD biosensor using the yeast Trichosporon cutaneum with oxygen probe takes only 15 minutes to detect organic pollution.
d) Miscellaneous biosensors- A graphite electrode with Cynobacterium andSynechococcus has been developed to measure the degree of electron transport inhibition during the photosynthesis due to certain pollutants e.g. herbicides. To detect phenol, phenol oxidase enzyme obtained from potatoes and mushrooms is used as a biosensor. Biosensors for the detection of polychlorinated biphenyls (PCBs) and chlorinated hydrocarbons and certain other organic compounds have also been developed. Biosensors employing acetylcholine esterase which can be obtained from bovine RBC can be used for the detection of organophosphorus compounds in water.
(Ref. no 1)