(P09-016-24) Development of Rice Bran Enhanced With γ-Aminobutyric Acid (GABA) by Fermentation of Aspergillus oryzae and Lactobacillus brevis

Objectives: Environmental sustainability is a critical issue attracting research interest globally. Rice bran is one of the major agricultural by-products in Asia, which is generally used as animal feed or discarded. It is worth investigating how to transform rice bran into functional foods with health benefits. Fermentation is known to enhance crops' nutritional value, such as γ-aminobutyric acid (GABA). This study aims to utilize Aspergillus oryzae (A. oryzae) and L. brevis) to develop fermented rice bran rich in GABA.

Methods: For fermentation, steamed rice was inoculated with A. oryzae to produce rice koji. The mixture of rice bran and shiro-nuka rice bran was saccharified by rice koji and then fermented by L. brevis to produce GABA. The level of GABA and total phenolic content in the fermented rice bran mixture (FRB) were determined by high-performance liquid chromatography and the modified Folin-Ciocalteu’s method. The antioxidant ability of FRB was assessed by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability test. The energy and nutrients of FRB, including protein, fat, total carbohydrate, and dietary fiber, were analyzed as well.

Results: The level of GABA in rice bran fermented by A. oryzae and L. brevis was 123.54 mg/g, whereas untreated rice bran showed only 1.25 mg GABA/g. The GABA in fermented shiro-nuka rice bran increased from not detectable to 37.18 mg/g. The total phenolic content also increased after fermentation. Comparison of different FRBs showed that 75% rice bran mixed with 25% shiro-nuka rice bran produced the highest GABA level (124.15 mg/g) and exhibited higher total phenolic content and DPPH free radical scavenging ability than others. Furthermore, the level of protein rose (26.9 g/100 g) while the dietary fiber (11.8 g/100g), fat (9.3 g/100g), and energy (338.9 Kcal/100 g) decreased in FRB. In addition, FRB was used to produce GABA-enriched functional foods like Instant miso soup and noodles according to the suggested dosage of GABA for stress reduction or sleep benefit.

Conclusions: The findings suggest that rice bran fermented by A. oryzae and L. brevis could markedly enhance the GABA concentration, facilitating the potential for developing rice bran into functional foods.

Funding Sources: This study is supported by the Ministry of Agriculture, Taiwan.