Exploring the Effects of Solid-State Fermentation on Polyphenols in Acanthopanax senticosus Based on Response Surface Methodology and Nontargeted Metabolomics Techniques

Abstract

In order to optimize the process of solid-state fermentation and understand the changes of active ingredients during fermentation of A.senticosus, we used response surface methodology to optimize the solid-state fermentation process of A.senticosus and analyzed the effect of fermentation on the active components of A.senticosus by nontargeted metabolomics techniques. The effects of fermentation conditions on polyphenol content were studied in terms of fermentation time, fermentation temperature, water content, and the inoculum level through Plackett–Burman design and response surface experiments. The optimized fermentation conditions were a fermentation time of 60 h, a fermentation temperature of 37°C, a water content of 55%, and an inoculum level of 12.5%, and the polyphenol content reached 10.25 ± 0.05 mg·g−1, which was 40% higher than that before fermentation. Furthermore, the metabolites and metabolic pathways of A. senticosus were analyzed before and after fermentation using nontargeted metabolomics techniques, and differences in metabolites were investigated based on the analysis of the principal components. The results showed that A.senticosus contained 57 phenolics, and a total of 12 polyphenolic metabolites were significantly different before and after fermentation (including phenols and isoflavonoids), among which the content of caffeic acid and its derivatives with antioxidant capacity was significantly increased, which may improve the antioxidant capacity of fermented A.senticosus. Therefore, solid-state fermentation opens new avenues for the clinical development and application of A. senticosus.