Astaxanthin is a valuable carotenoid, which has been approved as a food coloring by the US Food and Drug Administration and is considered as a food dye by the European Union (European Commission). This work aimed to attain Rhodosporidium toruloides mutants for enhanced astaxanthin accumulation using ultraviolet (UV) and gamma irradiation mutagenesis. Gamma irradiation was shown to be more efficient than UV for producing astaxanthin-overproducer. Among the screened mutants, G17, a gamma-induced mutant, exhibited the highest astaxanthin production, which was significantly higher than that of the wild strain. Response surface methodology was then applied to optimize the medium compositions for maximizing astaxanthin production by the mutant G17. The optimal medium compositions for the cultivation of G17 were determined as a peptone concentration of 19.75 g/L, malt extract concentration of 13.56 g/L, and glucose concentration of 19.92 g/L, with the maximum astaxanthin yield of 3021.34 µg/L ± 16.49 µg/L. This study suggests that the R. toruloides mutant (G17) is a potential candidate for astaxanthin production.
Gamma‐aminobutyric acid (GABA)‐enriched products (GEP) exhibited a wide range of pharmaceutical properties. In this study, anti‐inflammatory activity of GEP from Lactobacillus fermentum‐fermented water solution of rice bran was evaluated on lipopolysaccharide‐activated macrophage model. GABA content in L. fermentum‐fermented rice bran solution was determined up to 1.27 g/L. GEP was shown to inhibit the expression levels of inducible nitric oxide synthase and cyclooxygenase‐2 enzymes. Moreover, pretreatment of GEP attenuated the generation level of interleukin (IL)‐6, IL‐1β, tumor necrosis factor α, and monocyte chemoattractant protein‐1. Especially, the activation of signaling pathways due to nuclear factor‐κB (NF‐κB) and mitogen‐activated protein kinases (MAPKs) was interrupted in GEP‐exposed cells. Notably, molecular docking result showed a potential binding of GABA to Toll‐like receptor 4 with a binding energy of −3.88 kcal/mol, suggesting the role of GABA in suppression of Toll‐like receptor 4‐MAPK/NF‐κB signaling cascades. As the result, GEP from L. fermentum‐fermented rice bran solution could be suggested as a promising food for suppression of inflammatory responses.
Practical applications
GABA‐enriched products have been evidenced to possess various pharmaceutical properties and health beneficial effects. In this study, GABA‐enriched product from L. fermentum‐fermented rice bran solution exhibited the inhibition on inflammatory response in macrophages. Hence, it could be used as a potential ingredient for the mitigation of inflammatory responses.
Gamma-aminobutyric acid (GABA) is a potent bioactive component that widely exists in both plants and animals, has numerous health benefits. This study aimed to optimise the fermentation process conditions for the growth of Lactobacillus fermentum from rice bran extracts that have high potential to produce GABA. GABA content was assessed by thin-layer chromatography (TLC) method. In this study, fermenting conditions for medium production of GABA by L. fermentum from rice bran extracts were optimised. L. fermentum showed high potential for GABA-producing ability. Some factors influencing the GABA production such as carbon sources, nitrogen sources, mineral salt sources, substrate concentration of monosodium glutamate (MSG), pH, and the time of fermentation were investigated. When the L. fermentum is cultivated in the rice bran extracts medium supplemented with 1.5% lactose, 2% yeast extract, and 1% MSG with pH 6.0 in 48 h, this strain showed high GABA at a concentration of 736 mg/l.
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