Dynamic changes in the bacterial communities and metabolites of Moringa oleifera leaves during fermentation with or without pyroligneous acid

In this study, Moringa oleifera leaves (MOL) were fermented with or without pyroligneous acid (PA) for 3, 7, 14, and 30 days, respectively. The addition of PA enhanced the contents of acetic acid and true protein (P < 0.01), and decreased the contents of coliforms bacteria, pH (P < 0.01), non-protein nitrogen (P < 0.01) and ammonium nitrogen (P < 0.01). With the addition of PA, the abundance of Lactobacillus increased, but the abundance of Enterobacter decreased. Simultaneously, 754 metabolites were identified and the contents of most amino acids increased with the fermentation time prolong. With the PA addition, the contents of apigenin, arbutin, biotin, 2-methoxy-4-vinyl phenol, and 4-methoxy cinnamic acid increased, while the relative contents of skatole decreased. The metabolites detected were correlated with bacterial communities, especially Lactobacillus and Weissella. In conclusions, the addition of PA improved the fermentation quality, affected the bacterial communities and metabolites of fermented MOL.