Enhancement of GABA Production Utilizing Enzyme-Treated Rice Bran by Lactic Fermentation with pH Control

Abstract

　Optimum conditions for GABA production utilizing enzyme-treated rice bran by lactic fermentation were investigated. A culture containing 11% enzyme-treated rice bran (nutrient source) and 11.7% monosodium glutamate (additive substrate of GABA) inoculated with Lactobacillus brevis IFO12005 yielded a GABA content of 7.1% (w/w) when the pH was maintained at 5.0 throughout the fermentation period. This resulting GABA content is 4-5-fold higher than without pH control. In addition, the fermented product did not have an unfavorable flavor according to sensory testing. Thus, it is possible to add culture broth to food or drink products to enrich GABA content without damaging their original flavor.