Investigation of the solid-state fermentation of Astragalus membranaceus residue with Cordyceps militaris: effects on phenolic profile and in vitro neuroprotective activity

From the paper

Abstract

We developed a Cordyceps militaris-mediated solid-state fermentation (SSF) strategy to enhance phenolic antioxidants in Astragalus membranaceus residue (AR) and confer neuroprotective effects against oxidative stress. α-amylase (0.11 U/g), β-glucosidase (3288.2 U/g), protease (292.02 U/g), and esterase (33.08 U/g) were secreted, driving substantial increases in total phenols (106.61 %), flavonoids (27.35 %), and protein (136.24 %) while reducing polysaccharides in fermented AR-(FAR). Scanning electron microscopy revealed morphological alterations in FAR. Metabolomic profiling identified 129 differentially abundant metabolites, with antioxidant isoflavonoids, flavonoids, and phenolic acids exhibiting marked upregulation. KEGG enrichment confirmed activation of phenylpropanoid, flavonoid, and isoflavonoid biosynthetic pathways. HPLC-validation demonstrated markedly increased calycosin, calycosin-7-O-β-D-glucoside, formononetin, and ononin, while activities of key phenolic synthases phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumarate-CoA ligase were significantly enhanced in FAR. FAR mitigated H₂O₂-induced oxidative stress by suppressing reactive oxygen species and malondialdehyde while restoring superoxide dismutase activity. This study shows SSF bioprocessing of AR enhances food innovation while reducing agro-waste.