Determination of L-glutamate using flow injection analysis with immobilized L-glutamate oxidase reactor.

L-Glutamate oxidase (GOD) and horseradish peroxidase (HRP) were covalently coupled on alkylamine pretreated controlled pore glass (CPG) by means of glutaraldehyde. The immobilized enzymes were packed into a teflon tube and used in flow injection analysis (FIA) system for L-glutamate determination. A good linearity range was obtained at 0.1-2.0 mM, and the coefficient of variation was 0.7% (n = 8). More than 80 samples were measured within an hour. The stability of the immobilized GOD reactor was good, retaining 50% of its initial activity after 4 months storage in buffer at 4 degrees C. When the concentration of L-glutamate remained lower than 2.5 mM, the determination of L-glutamate in this system was not affected by pH and temperature within the range of 6.0-8.0 and 20-35 degrees C, respectively. The system was applied to determine L-glutamate in broth samples during L-glutamate fermentation and good correlations were achieved between results obtained with the FIA system, L-glutamate oxidase kit and Warburg's method.