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Higher alcohols are not only the key flavor substance but also the precursor of other flavor substances in Baijiu. In the metabolic pathway of higher alcohols, alcohol dehydrogenase (ADH) plays an important role and its genes can be used as a marker gene for analyzing the producer of higher alcohols. In this study, the degenerate primers of Zinc-dependent long-chain ADH gene (L.adh) were designed and applied to investigate the diversity of L.adh in different Daqu (HT, SC and SD). The results showed that the degenerate primers were able to amplify the fragment of L.adh and had good coverage in high-throughput sequencing. The diversity and composition of L.adh in the three kinds of Daqu were different and the diversity of L.adh in SC was the highest while HT was the lowest. The predominant L.adh in SC and HT were form Bacillus (54%–78%) and Aspergillus (64%–66%), respectively, and the predominant L.adh in SD were from Aspergillus (7%–51%) and Enterobacter (2%–47%). In addition, L.adh from bacteria and fungi could be clustered into one evolutionary branch and divided into 10 clusters. The findings of this study will provide a new perspective for evaluating the potential microorganisms associated with higher alcohol synthesis in Daqu and reference for selecting suitable Daqu in the production of Baijiu.

Antimicrobial peptides, as natural preservatives, had a wide application prospect in the food industry due to their high efficiency, stability and safety. To determine the optimal fermentation condition for producing antifungal peptides from Lacticaseibacillus paracasei ALAC, this study took the antibacterial zone as the indicator, the effects of fermentation time, fermentation temperature, initial pH and inoculum volume on the production of antimicrobial peptides were studied by single factor experiments and the response surface optimization was performed using Box-Behnken design on three parameters that significantly affect fermentation time, inoculation amount, and initial pH. Results showed that, when the inoculum amount of 4%, initial pH of 7.0, and fermentation time of 24 h, under this condition, the antibacterial substances produced by fermentation had the best antibacterial activity, with a diameter of 17.33±0.17 mm, this result could provide a theoretical basis for the production of antimicrobial peptide powder and its application in food.

Fungal spoilage of food is a worldwide concern prompting the development of many antimicrobial agents and applications. In this study, the cell-free supernatant (CFS) of Lacticaseibacillus paracasei ALAC-4 had a significant inhibition effect on fungi. The CFS with antifungal activities were combined with chitosan (CS) matrix to prepare an active packaging CS-CFS films by using a solvent casting method and used for the packaging of Mongolian cheese for 15 days during storage at 4 ± 1℃. The optimized formulation of the film were 1.25% (w/v) chitosan, 1.75% (w/v) gelatin, 0.3% (v/v) glycerol, and 9.6% (w/v) CFS. It was found that CS-CFS films exhibited strong antifungal activities against molds and yeasts, especially Candida albicans, and also had excellent mechanical properties. Additionally, FTIR spectroscopy indicated that hydrogen bonds between the CFS and CS formed, and there was a smooth surface, compact cross-section observed in SEM morphologies of CS-CFS films. Furthermore, CS-CFS film also displayed a strong antifungal effect against molds and yeasts on cheese surface. These results suggest that the chitosan-based CS-CFS film has a promising application for Mongolian cheese and food preservation.

Fermented porridge is usually made though the process of natural fermentation of grains with higher starch. Organic acids are the main flavor compounds in fermented porridge. However, the understanding of the correlation between the microbial communities and organic acids is limited in the fermentation process of traditional Chinese sour porridge (CSP). In this study, the dynamic of bacterial community and organic acids was investigated and the correlation between bacterial communities and organic acids was revealed during the fermentation process of CSP. The results showed that the richness and diversity of the bacterial communities at initial state (0h) were significantly higher than other period and the concentration of 9 organic acids (oxalic acid, tartaric acid, malic acid, lactic acid, acetic acid, citric acid, and succinic acid) increased with the fermentation process. Pediococcus and Lactobacillus were the dominative genus in the fermentation process of CSP and the fermentation process of CSP can be divided into three stages, with 0 h as the initial stage, 6–18 h as the second group and 24–36 h as the third based on PCA and cluster analysis. Moreover, 20 bacteria genus had significant correlation with (|ρ|>0.7) organic acids based on O2PLS analysis and The Lactobacillus and Acinetobacter were positively correlated with seven (succinic acid, tartaric acid, lactic acid, oxalic acid, acetic acid, malic acid and succinic acid) and four (tartaric acid, acetic acid, lactic acid, and α-ketoglutarate) organic acids respectively. Clostridium, Paenibacillus, Cupriavidus, Shinella, Streptococcus, Flavobacterium, Enterobacteriaceae, Cyanobacteria, Pseudomonas, Ralstonia, Microbacterium, Bradyrhizobiaceae, Escherichia-Shigella, Acidovorax, Leuconostoc, Alphaproteobacteria, Pediococcus, and Mitochondria were negatively correlated with organic acids in the fermentation process of CSP.