Novel, thick-film biosensors have been developed for the determination of L-glutamate in foodstuffs. The sensors were prepared by immobilization of L-glutamate oxidase by using polycarbamylsulfonate-hydrogel on a thick-film sensor. L-Glutamate oxidases obtained from Streptomyces sp. with different degree of purification were compared with their characteristic response to L-glutamate at different conditions and for their specificity, inhibition, and storage properties. These sensors were applied to determine monosodium glutamate in soy sauce samples and show good correlation with colorimetric method.