Bacteria are an important part of wine ‘microbial terroir’ and contribute to the formation of wine flavor. Based on high-throughput sequencing and non-targeted metabonomic technology, this study first explored the bacterial composition and its effect on the aroma formation of spontaneously fermented ‘Cabernet Sauvignon’ (CS) wine in the Eastern Foot of Helan Mountain (EFHM), Ningxia. The results showed that there were significant differences in bacterial communities during fermentation of CS grapes harvested from different sub-regions of EFHM, with the earlier-established vineyard obtaining more species. The level of bacterial diversity initially decreased and then increased as the fermentation proceeded. Malolactic fermentation (MLF) was spontaneously initiated during alcohol fermentation (AF). Pantoea, Lactobacillus, Rhodococcus, Fructobacillus, and Komagataeibacter were the core bacterial genera in the fermentation mixture. Lactobacillus contributed to the synthesis of methyl and isobutyl esters and the formation of red and black fruity fragrances of wine. Fructobacillus was closely related to the synthesis of aromatic alcohols and the generation of floral flavors.

• Hanseniaspora uvarum dominated the non-Saccharomyces yeast population during spontaneous fermentation. • H. uvarum increases the ethyl ester content in grape wine by 48.54–110.92 % through mixed fermentation. • H. uvarum reduced the acetic acid content of grape wine from 10.81 % to 17.78 % through mixed fermentation. • The tropical fruit flavor of grape wine benefits from the increased production of ethyl esters.

The eastern foothills of the Helan Mountains in the Ningxia region (Ningxia), is a Chinese wine-producing region, where Cabernet Sauvignon is the main grape cultivar; however, little compositional or flavor information has been reported on Ningxia wines. Oenological parameters, volatile profiles, and phenolic profiles were determined for 98 Ningxia Cabernet Sauvignon wines from the 2013–2018 vintages, as well as 16 from Bordeaux and California, for comparison. Ningxia wines were characterized by high ethanol, low acidity, and high anthocyanin contents. Multivariate analysis revealed that citronellol and 12 characteristic phenolic compounds distinguish Ningxia wines from Bordeaux and California wines. The concentrations of most phenolic compounds were highest in the 2018 Ningxia vintage and decreased with the age of the vintage. To our knowledge, this is the first extensive regionality study on red wines from the Ningxia region.