Zheng Wang

Understanding the composition of the bacterial community on the epidermis of wine grapes and in winery environments, as well as the response of grape epidermal bacteria to climatic factors, plays a significant role in ensuring grape health and promoting grape conversion into wine. This study utilized high-throughput sequencing to explore the composition of the bacterial community on the wine grape epidermis and representative wineries of three sub-regions of the Eastern Foothills of Helan Mountain, Ningxia. The results showed that the bacterial diversity and richness in the Yongning (YN) sub-region were the highest, with Qingtongxia (QTX) having the lowest levels of grape epidermal bacteria. The bacterial diversity and richness were the highest in Yinchuan (YC) and the lowest in YN in the winery environment (p < 0.05). The composition of dominant bacteria on the grape epidermis and in winery environments of the three sub-regions was not different at the phylum and genus level, but the levels of these dominant bacteria were different among the sub-regions. There was a correlation between grape epidermal bacteria and climatic factors. Approximately 93% of the bacterial genera on the grape epidermal genera in the three sub-regions are present in the winery environment and contain all the dominant bacterial genera on the epidermis.

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.