Screening and evaluation of high stress tolerance, high esterase activity and safety of Oenococcus oeni strains adapt to challenging conditions in Northwest China wine

Malolactic fermentation is an essential process in winemaking. In Northwest China, increasing alcohol content due to global warming and rapid temperature drops during fermentation complicate the initiation and completion of MLF. In this study, 20 Oenococcus oeni strains from Ningxia wine region were selected to identify strains with superior fermentation performance. The strains NXH-58, NXH-79, NXH-86, NXG-103, and NXH-20 exhibited high tolerance to various wine stress factors and demonstrated high esterase activity. Under combined stress conditions, O. oeni NXG-103 exhibited the highest vitality, with an average viable count of 2.72 × 10⁷ CFU/mL, followed by NXH-20 with 1.70 × 10⁷ CFU/mL, both of which were significantly higher than those of commercial strains Oeno 1. Fermentation experiments showed that O. oeni NXG-103 and O. oeni NXH-20 promptly and completely reduced L-malic acid in Cabernet Sauvignon wines within 28 and 32 days, respectively. Post-MLF analysis of wine volatile compounds revealed wines fermented with high esterase activity strains had higher levels of esters, advanced alcohols, and terpenes. Furthermore, the concentrations of biogenic amines and ethyl carbamate in the wines fermented by these two O. oeni strains were lower than commercial strain, approximately at 9.0 mg/L and 4.8 μg/L, respectively. This study underscores the importance of selecting excellent strains and understanding their MLF characteristics, laying a foundation for developing indigenous Chinese wine starter cultures and enhancing wine quality. • Twenty indigenous Oenococcus oeni strains and their stress tolerance were studied. • Three strains have good tolerance to high ethanol, high SO 2 and low temperature. • Richer aroma and faster fermentation were linked to the esterase activity of strains. • The screened strains produced less biogenic amines and ethyl carbamate in wines.