Nutritional composition and physicochemical properties of fermented cassava (Manihot esculenta Crantz) during solid-state fermentation: Metabolites and microbial communities influenced by medium-temperature Daqu

• Metabolites and microbial communities were investigated in fermented cassava. • Enhanced fermentation of cassava with medium-temperature Daqu could significantly reduce the content of cyanogenic glycosides. • The microbial communities were closely related to non-volatile metabolites. Guangxi cassava ( Manihot esculenta Crantz) was used with medium-temperature Daqu as the fermentation agent to enhance the nutritional value and physicochemical properties of the products through solid-state fermentation. Using an orthogonal experimental design, the optimal fermentation conditions were determined as follows: inoculation volume of 8%, moisture content of 60%, and fermentation time of 48 h. Under this optimised condition, the amino acid and reducing sugar content of fermented cassava reached 37.51 and 18.54 mg/g, and the contents of leucine, valine and phenylalanine were significantly increased by 300%, 231.03% and 120.21%, respectively. Additionally, the anti-nutritional factors linustatin and linamarin were effectively reduced. Metagenomic sequencing results revealed that Enterococcus, Enterobacter , and Lactococcus were the dominant bacterial genera, with relative abundances of 52.15, 18.28, and 14.40%, respectively. Amino acids and their derivatives, along with organic acids, emerged as the main differentially expressed metabolites. Among the volatile metabolites in fermented cassava, palmitic acid, elaidic acid, and linoleic acid were the most abundant, reaching concentrations of 51.91, 48.35, and 29.72 μg/g, respectively.