Optimization of Solid-State Fermentation Conditions of Astragali Radix Residues and Changes of Its Nine Constituents Content Before and After Fermentation

Background: For the last few years huge quantity of herb residues are discharged in China, and so far there is not a good solution. The current methods of disposal and utilization of herb residues (stacking, incineration, and landfill) were not only great harmful to the ecological environment, but also cause the waste of medicinal herb resources. The fermentation can further decompose and transform the active ingredients and nutrients in herb residue, so the fermentation technology has good application prospect in the treatment of herb residues. In this study, we investigated the applicability of fermentation processes with the Aspergillus niger (ACCC 30583) strain for the reuse of Astragali Radix residues (ARR) by comparing the content changes of its nine constituents before and after fermentation. The contents of total protein and crude fat in the ARR were determined via near-infrared scanning; the iron, copper, zinc, and manganese contents were assayed with atomic absorption spectroscopy, the calycosin-7-glucoside and astragaloside Ⅳ content were determined by HPLC, and the polysaccharide content was determined via phenol sulfuric acid spectrophotometry. Results: The optimum fermentation conditions for ARR with ACCC 30583 was culture medium content 60%, fermentation time 5 days, and fermentation temperature 28 ℃. Compared with the residues before fermentation, the contents of total protein, calycosin-7-glucoside, astragaloside Ⅳ, Astragali Radix polysaccharides (ARP), and manganese increased significantly, the iron content decreased significantly, and the crude fat, zinc, and copper contents exhibited no significant changes. Conclusions: The solid fermentation of ARR with the Aspergillus niger (ACCC 30583) strain effectively promoted the separation of astragaloside Ⅳ and ARP from ARR, which provided methodological basis for the effective reuse of herb residues.