Abstract: Objective: This study aimed to evaluate the stress resistance and malolactic fermentation ability of an acid-tolerance mutant strain of Oenococcus oeni for the purpose of providing a basis for the development of commercial wine fermentation starters. Methods: A acid-tolerant mutant b1, obtained by N+ ion implantation mutagenesis, was tested for the effect of various environmental stress factors and their combinations as well as wine-model conditions on its growth, L-malic acid degradation rate and β-glycosidase activity. Furthermore, we assessed the malolactic fermentation (MLF) ability of mutant b1. Results: The L-malic acid degradation rate and β-glycosidase activity of b1 were higher than those of the other strains under the conditions: pH 3.0, alcohol concentration of 14% and malic acid concentration of 3 g/L. pH had the greatest influence on the growth, L-malic acid degradation rate and β-glycosidase activity of b1, alcohol concentration was in the middle, and L-malic acid concentration was least effective. When the alcohol concentration of the model wine was 14%, the L-malic acid consumption of strain b1 was 1.493 2 g/L, which was 1.41 and 1.26 times as high as that of O. oeni SX-1b and 31-DH, respectively, and it had the highest β-glucosidase activity. Conclusion: Acid-tolerant mutant b1 has good stress resistance and malolactic fermentation ability. Therefore, it has the potential to be used as a commercial starter .

Key words: Oenococcus oeni, growth, deacidification, β-glycosidase, malolactic fermentation