Aims: Acetaldehyde is the major carbonyl compound formed during winemaking and has implications for sensory and colour qualities of wines as well as for the use of the wine preservative SO2. The current work investigated the degradation of acetaldehyde and SO2-bound acetaldehyde by two commercial Oenococcus oeni starters in white wine. Methods and Results: Wines were produced by alcoholic fermentation with commercial yeast and adjusted to pH 3.3 and 3.6. While acetaldehyde was degraded rapidly and concurrently with malic acid at both pH values, SO2-bound acetaldehyde caused sluggish bacterial growth. Strain differences were small. Conclusions: Efficient degradation of acetaldehyde can be achieved by commercial starters of O. oeni. According to the results, the degradation of acetaldehyde could not be separated from malolactic conversion by oenococci. While this may be desirable in white winemaking, it may be necessary to delay malolactic fermentation (MLF) in order to allow for colour development in red wines. SO2-bound acetaldehyde itself maybe responsible for the sluggish or stuck MLF, and thus bound SO2 should be considered next to free SO2 in order to evaluate malolactic fermentability. Significance and Impact of the Study: The current study provides new results regarding the metabolism of acetaldehyde and SO2-bound acetaldehyde during the MLF in white wine. The information is of significance to the wine industry and may contribute to reducing the concentration of wine preservative SO2.