Comparative Study on the Fermentation Characteristics of Selective Lactic Acid Bacteria in Shanxi Aged Vinegar: Pure Culture Versus Co-Culture

The diversity of the microbial community structure plays a crucial role in the flavor and nutritional value of Shanxi aged vinegar in fermentation. Illumina Miseq high-throughput sequencing identified thirteen bacterial genera, with Lactobacillales (44.89%) and Acetobacter (21.04%) being the predominant species. Meanwhile, the fermentation characteristics of selected lactic acid bacteria strains isolated from Shanxi aged vinegar were studied in different media. The results showed that the biomass, and physical and chemical indices, as well as flavor compounds of the four strains of lactic acid bacteria in the simulated vinegar fermented grains medium were superior to those in barley and pea medium and sorghum juice medium. The bacterial interaction was conducted to investigate the effects on growth, the physicochemical indices, and flavor substances in order to determine the optimal combination. Furthermore, the interaction between pure cultures and co-cultures of lactic acid bacteria in a simulated vinegar culture medium was investigated, with a focus on the impact of this interaction on strain growth, fermentation characteristics, and flavor compound production. Compared with the pure culture, when strains L7 and L729 were co-inoculated, the reducing sugar content was 0.31 ± 0.01 g/100 g, total acid content was 3.02 ± 0.06 g/100 g, acetoin content was 2.41 ± 0.07 g/100 g, and total organic acid content was 3.77 ± 0.17 g/100 g. In terms of flavor compounds, the combined culture system exhibited higher levels of esters, aldehydes, and acids compared to pure cultures or other co-culture systems. This study revealed the fermentation characteristics of selected lactic acid strains in Shanxi aged vinegar under different conditions and their interaction in simulated vinegar fermentation media, which could provide theoretical support for the safety and health evaluation of aged vinegar.