Antioxidant compounds from rice bran fermentation by lactic acid bacteria

Abstract

This research aims to study antioxidant compounds of two rice bran strains (Khao Bahn Nah and Thai jasmine) in different moisture contents (50 and 75% w/v) with solid state fermentation (SSF) by lactic acid bacteria (LAB) as Lactobacillus casei and Lactobacillus plantarum . After the incubation at 24, 48, and 72 h, the highest total polysaccharide (38.77 ± 1.21 mg/mL) found in Thai jasmine without SSF at 75% w/v moisture after 72 h. While the rice bran extract with SSF by both LAB presented higher amount of phenolic content and antioxidant activity than the rice bran extract without SSF, particularly Khao Bahn Nah extract with 50% w/v moisture by L. plantarum at 48 h showed the maximum phenolic compound (2.85 ± 0.05 mg/mL). As well as the best percentage of antioxidant activity found in both fermented rice bran extract strains with 50% moisture by L. casei with the same incubation time at 48 h (Thai jasmine = 78.79% and Khao Bahn Nah = 78.49%). HPLC chromatogram revealed the composition of phenolic compounds in both rice bran extract strains, mainly in Thai jasmine with SSF by L. casei at 50% w/v moisture for 48 h displayed the best quantity of tocopherol (4.51 ± 0.38 mg/L), gamma-oryzanol (3.61 ± 0.15 mg/L), coumaric acid (14.47 ± 1.20 mg/L) and ferulic acid (35.23 ± 0.82 mg/L). From the potential of antioxidant activity and total phenolic content of rice bran extract showed the possibility of adding value to the agricultural residue. Therefore, the rice bran extract by SSF may be applied to become a functional food product in the future.