The effects of Metschnikowia pulcherrima and high glucose osmolality on S. cerevisiae pyruvate dehydrogenase pathway (PDH) by-pass were examined by varying the starting sugar concentration of synthetic grape juice and the inoculation ratio of S. cerevisiae to M. pulcherrima. The findings revealed that M. pulcherrima and osmolarity impacted S. cerevisiae’s PDH by-pass. The inoculation concentration of M. pulcherrima significantly affected pyruvate decarboxylase (PDC) activity and acs2 expression when the initial sugar concentration was 200 g L⁻¹ and 290 g L⁻¹. The osmolarity caused by the initial sugar (380 g L⁻¹) significantly influenced the enzymatic activity of S. cerevisiae, which decreased PDC and acetaldehyde dehydrogenase (ALD) activities while increasing Acetyl-CoA synthetase (ACS) activity. The reduction in acetic acid in the wine was caused by M. pulcherrima altering the initial sugar concentration faced by S. cerevisiae, which in turn affected enzymatic activity. The alteration of enzyme activity and accumulation of primary metabolites revealed why mixed fermentation could reduce the acetic acid content in wine by altering the enzymatic activity and affecting the expression of several key genes. The M. pulcherrima inoculation levels had no significant effect on the acetic acid and glycerol concentration in the same fermentation medium.

Integrated assessments of commercial Chardonnay wines from East Asia remain limited. This study compared wines from eight wineries—four in the Shandong Peninsula (China) and four in the Chugoku region (Japan)—across two vintages (2022–2023), with one bottle analyzed per winery–vintage combination, yielding 16 commercial wine observations. Physicochemical, HS-SPME-GC-MS volatile, sensory, and growing-season climate data were integrated. Among the sampled commercial wines, Chugoku wines generally showed higher acid retention and stronger floral–citrus characteristics, whereas Shandong wines were more fruit-forward, with higher fruity ester contributions in several 2023 samples. Exploratory climate–composition analysis identified a negative association between GDD and total terpenoids after FDR correction, whereas other associations did not remain significant after multiple-testing correction. These results indicate regional and vintage-associated differences among the sampled commercial wines. Because vinification practices and post-bottling factors were not fully controlled, climate–composition relationships should be interpreted as exploratory rather than causal.