The facilitation between Staphylococcus carnosus M43 and Zygosaccharomyces rouxii Y-8, and as starter on the quality of broad bean paste

Zygosaccharomyces rouxii ( Z. rouxii ) and Staphylococcus carnosus ( S. carnosus ) are fundamental taxa in spontaneous bean-based food fermentation , playing a vital role in flavor generation and macromolecule degradation. The present study aimed to investigate the biological mechanisms underlying the interaction between Z. rouxii Y-8 and S. carnosus M43 in BBP (broad bean paste) moromi by mono- and co-culture. It was found that the biomass of Z. rouxii and S. carnosus was higher in co-culture than that in mono-culture ( p  < 0.05), indicating that a facilitation relationship among them. Moreover, the observed intensity of facilitation (OIF) peaked at 0.479 ± 0.002 under aerobic conditions, which was higher than that under anaerobic conditions (0.147 ± 0.014). Furthermore, the facilitative microbial interaction showed the stability and robustness during co-culture with different inoculum proportions (1:3, 1:5, 1:7, 1:10) and cell passage from 1 to 4 generations. Physical separation co-culture and acetic acid tolerance test revealed that acetic acid played a crucial role in regulating the interaction between Z. rouxii (R 2  = 0.6955) and S. carnosus (R 2  = 0.7097), with metabolic complementarity and inhibition alleviation as the underlying mechanisms. Additionally, Z. rouxii and S. carnosus as starter could enhance the accumulation of flavor compound, and accelerate the maturity of BBP fermentation. The dissection of interaction between Z. rouxii and S. carnosus provided valuable insights for revealing the complex web of relationships among microbiota and the development of microbial starter in BBP brewing ecosystem.