## 4 Discussion
Nevertheless, it will return to the original count after the first week. In this study, the viable cell counts of all strains dropped throughout eight days. After 12 days, the viable cell counts of A7, A50, and B28 declined to vary degrees. _O. oeni_ 31-DH and _L. plantarum_ BV-S2 are relatively stable. A7, A50, and B28 decrease and then increase, but MLF can be continued. Genetic differences can explain the differences in acid reduction among strains isolated from the same region. Being able to survive in 17% ethanol does not necessarily help finish MLF. When changing from the nutrient-rich environment to the nutrient-poor environment, and with too many factors affecting growth, the strains will face many difficulties that threaten their growth. The inhibitory effects of polyphenols in wine on the growth of LAB and the existence of yeast secondary metabolites lead to the incompatibility between yeast and LAB [2]. In comparison, A7 has the potential to become an excellent MLB. [PERSON] et al. [39] isolated 204 strains from red wine in the Rioja region, of which 98.5% were _O. oeni_. [PERSON] et al. [40; 41] isolated strains from wines of different years and fermentation stages in different wineries in Spain. Moreover, it identified that _O. oeni_ was the dominant strain. The proportion of other strains was between 2% and 10%. [PERSON] et al. [42] isolated and identified 150 strains from wines from the Apulia region, most of which were _L. plantarum_. Due to grape variety, wine pH, ethanol, and other factors, the selection of MLB strains becomes more diverse. _O. oeni_ is no longer the single choice in the process of MLF. The tolerance of _L. plantarum_ to ethanol and its more enzymatic properties make it dominant in the future oncology process. Compared with the aroma composition and content of non-MLF wine, it was found that the composition and content of esters in all wines increased after MLF. Compared with the control strains, the number and content of esters produced by A7, A50, and B28 were relatively higher. Especially A7 had high content in ethyl acetate, isoamyl acetate, ethyl caproate, hexyl acetate, ethyl heptanoate, ethyl trans-2-hexenoate, isoamyl caproate, methyl octanoate, ethyl octanoate, ethyl nonanoate, and isobutyl octanoate. Giving the wine some pleasant aroma, such as fruit, flower, and honey, is essential. Although the total amount of wine alcohols decreased to 78.17 mg/L, 71.31 mg/L, and 73.70 mg/L (Table S1) after MLF, the difference was insignificant compared to control strains. The differences were mainly concentrated in less harmful aromas such as isoamyl alcohol (almond taste, astringent taste) and 3-methylthiopromal (garlic flavor, raw potato flavor). Moreover, increase the variety of flower aroma composition. Together with esters and other volatile aroma substances, it enriches wine and reduces undesirable aroma. Compared with control strains, A7 contains benzaldehyde, nonanal, phenylacetaldehyde, 2,4-di-tert-butylphenol and other substances closely related to wine fermentation metabolism was the highest. These substances contribute to the balance of wine taste and the improvement of sensory quality. The variation in aroma content and variety is partly due to \(\beta\)-D glucosidase. Some studies have found that _L. plantarum_ is one of the primary sources of \(\beta\)-D glucosidase in oenology [32]. An essential role of \(\beta\)-glucosidase in oenology process is to promote the production of aromatic compounds in wine, thus affecting the aroma and taste of wine [43]. Furthermore, \(\beta\)-glucosidase also changes the composition of phenols in wine by hydrolyzing compounds [44]. A7, A50, and B28 had specific \(\beta\)-D glycosidase activity. It could be seen from the phylogenetic clustering tree that they were all in different branches, which made it possible for MLF to produce more diverse aroma components.