Microbial and genes diversity analysis: Relationship between starch conversion and carbohydrate metabolism during Niandoubao fermentation via the glutinous proso millet (GPM) process

Niandoubao is an ancient Chinese northeast fermented food mainly manufactured by glutinous proso millet (GPM). Succession and carbohydrate metabolism of complex microorganisms during GPM soaking (primarily spontaneous fermentation) may affect pH and starch content and then change the texture properties of Niandoubao. This study determined physicochemical parameters during the GPM spontaneous fermentation period, including pH, starch components, and reducing sugar content. Analysis of microbial diversity and the functional pathways related to these physicochemical parameters were also performed by 16S rDNA and metagenomics sequencing. Results showed that the pH value significantly decreased during the GPM spontaneous fermentation process. The total starch content and amylopectin content of fermented samples decreased significantly (p