Multi-microorganism solid-state fermentation (SSF) is a traditional technique to produce fermented foods. However, the fermentation kinetics is difficult to establish due to the irregular and complex growth and metabolism profiles of the microorganisms. In this work, the SSF of vinegar was described and predicted for the first time by using two-stage kinetics. The in situ and in vitro kinetics of cell growth, product formation, and substrate utilization of the predominant microorganisms Acetobacter and Lactobacillus with R-2 more than 0.98 were analyzed using Logistic, Luedeking-Piret, and Luedeking-Piret-like modes, respectively. Ethanol, lactic acid, and acetic acid were found to be the main factors responsible for the temporal variation of fermentation profiles. Potential interactions between predominant microorganisms were revealed by in vitro SSF. Acetic acid mainly produced by Acetobacter was proven the main factor for the two-stage profiles, and its modulating role for microbial growth and metabolism was more important than that of lactic acid and ethanol. The thresholds of acetic acid to the negative specific growth rate were 3.05 and 1.68 g/100 g of Cupei for A. pasteurianus and L. helveticus, respectively. These results provide the theoretical modules to understand the SSF of cereal vinegars for further monitoring and modulation.

Bioaugmentation technology may be an effective strategy to improve the solid-state fermentation rate and utilization of raw materials for traditional vinegar production. The relationship between bacteria and fermentation process was analyzed to rationally design and perform bioaugmented solid-state fermentation of the Tianjin Duliu mature vinegar (TDMV). Fermentation process was highly correlated with Acetobacter, Lactobacillus , and Pediococcus contents, which were the core functional microorganisms in TDMV fermentation. Pediococcus acidilactici AAF1-5 was selected from 20 strains to fortify the fermentation due to its acidity and thermal tolerance. Bioaugmentation was performed in the upper layer of TDMV fermentation. P. acidilactici AAF1-5 colonized and then spread into the lower layer to improve the fermentation. Result showed that the fermentation period was 5 days less than that of the control. Meanwhile, the non-volatile acid, lactic acid, amino nitrogen, and reducing sugar contents in the bioaugmented TDMV increased by 53%, 14%, 32%, and 36%, respectively, compared with those in the control. Bioaugmentation with P. acidilactici AAF1-5 not only improved the utilization of starch from 79% to 83% but also increased the bacterial community diversity.