Haruo Obana

A potentiometric microbial sensor based on immobilized escherichia coli for glutamic acid

The sensor consists of immobilized E. coli (which contains glutamate decarboxylase) and a carbon dioxide gas-sensor. Continuous introduction of sample solution into a flow system incorporating the sensor gives a potential which increases until a steady state is reached after 5 min. Measurements can also be made with only a 1- or 3-min introduction period with little loss of sensitivity. Calibration plots of mV measurements vs. logarithmic glutamic acid concentration are linear in the range 100–800 mg l-1. The sensor is highly selective, stable and reproducible. It has been applied to the determination of glutamic acid in fermentation broths.

Amperometric determination of total assimilable sugars in fermentation broths with use of immobilized whole cells

A microbial sensor consisting of immobilized living whole cells of Brevibacterium lactofermentum and an oxygen electrode was prepared for continuous determination of total assimilable sugars (glucose, fructose and sucrose) in a fermentation broth for glutamic acid production. Total assimilable sugars were evaluated from oxygen consumption by the immobilized microorganisms. When a sample solution containing glucose was applied to the sensor system, increased consumption of oxygen by the microorganisms caused a decrease in the dissolved oxygen around the Teflon membrane of the oxygen electrode and the current of the electrode decreased markedly with time until steady state was reached. The response time was ≈ 10 min by the steady state method and 1 min by the pulse method. A linear relationship was found between the decrease in current and the concentration of glucose (<1 mM), fructose (<1 mM) and sucrose (<0.8 mM). The ratio of the sensitivity of the microbial sensor to glucose, fructose and sucrose was 1.00:0.80:0.92. The decrease in current was reproducible to within 2% of the relative standard deviation when a sample solution containing glucose (0.8 mM) was employed for experiments. The selectivity of the microbial sensor for assimilable sugars was satisfactory for use in the fermentation process. The additivity of the response of the microbial sensor for glucose, fructose and sucrose was examined. The difference between the observed and calculated values was within 8%. The microbial sensor was applied to a fermentation broth for glutamic acid production. Total assimilable sugars can be determined by the microbial sensor which can be used for more than 10 days and 960 assays.

Sugar (Glucose, Fructose, Sucrose) Sensor for Fermentation Control

Cane and beet molasseses, which are used as the raw materials of fermentation processes, mainly contain three kinds of sugars, glucose, fructose and sucrose. Accordingly, on-line measurements of those sugars would be required for advanced fermentation control.’ A glucose consisting of immobilized glucose oxidase and an oxygen electrode can be used for the determination of glucose. However, the determination of fructose is quite tedious. On the other hand, three sugars can be specifically determined by a glucose sensor system consisting of chemical isomerization and chemical hydrolyzation reactors. The schematic diagram of a sugar sensor system is shown in FIGURE 1. The principles of each sugar measurement are as follows: (1) Glucose measurement4lucose + 0, Glucono-lactone + glumrc oxidass