Amperometric L-glutamate sensor using a novel L-glutamate oxidase from Streptomyces platensis NTU 3304

Abstract

Streptomyces platensis NTU 3304, isolated from soil samples, produces extracellular L-glutamate oxidase in liquid culture. Strains of this species have never been reported to be able to produce this enzyme. The purified enzyme was immobilized onto a cellulose triacetate membrane which was held at an oxygen electrode. The sensor was specific to L-glutamate in accordance with the properties of the novel L-glutamate oxidase. The time required for each assay in batch operation was less than 3 min. A linear relationship is observed between the decrease in dissolved oxygen and the concentration of L-glutamate between 20 and 140 mg l −1 (ca. 0.12 and 0.84 mM). The sensor retained 95% of its original activity after 400 assays over a period of 3 weeks. The sensor was applied to determine the concentration of L-glutamate in broth samples during L-glutamic acid fermentation. Good correlations were achieved between results obtained with the sensor and by enzymatic analysis using glutamate dehydrogenase.