Production of Xylaria nigripes-fermented grains by solid-state fermentation and an assessment of their resulting bioactivity

Abstract

Solid-state fermentation was applied to achieve synergistic effects between the bioactivities of Xylaria nigripes (XN) mycelium and whole grains, including brown rice, red beans, mung beans and soybeans. After culturing in cooked grains for 30 days, the XN-mycelium becomes intertwined with the grains. The scavenging activity on DPPH (α-diphenyl-β-picrylhydrazyl) radicals, inhibitory activity on lipid peroxidation and reduction potential were determined to evaluate the antioxidant activities. Anti-inflammatory activity was determined by measuring the concentration of nitric oxide in lipopolysaccharide-induced RAW264.7 cells and by assessing the cyclooxygenase-2 (Cox-2) activity with a commercial enzyme-linked immunosorbent assay kit. Compared to unfermented grains, XN-fermented grains exhibited greater antioxidative, anti-inflammatory and neuroprotective potential. XN-fermented red beans exhibited the highest bioactivities. Ethanol (70%) was a more effective solvent than hot water to extract bioactive compounds. The IC50 for ethanol extract of the XN-fermented and unfermented red beans on DPPH scavenging activity were 2.0 ± 0.1 and 2.7 ± 0.1 mg/ml, respectively, and on lipid peroxidation inhibition were 0.97 ± 0.1 and 3.44 ± 0.1 mg/ml, respectively. For Cox-2 inhibition and PC12 protection, ethanol extract of the XN-fermented red beans showed 36.5 ± 0.5% and 27.2 ± 1.1%; while ethanol extract of the unfermented red beans were 24.9 ± 1.5% and 25.4 ± 2.2%.