Fig 1.

Anaerobic batch cultures of Lb. delbrueckii subsp. bulgaricus cocultivated with S. cerevisiae in the absence of added CO₂ (culture sparged with 100% nitrogen gas) (A), in pure culture in the absence of added CO₂ (culture sparged with 100% nitrogen gas) (B), or in pure culture with sparging of the culture vessel with a 2% CO₂–98% N₂ gas mixture (C). □, optical density; ▼, lactose; ◆, glucose; ●, galactose; ■, lactate. The dashed lines in panels A and C represent the percentage of CO₂ in the off-gas. Cultures were run in duplicate. The duplicates differed by less than 10%, and the results for a single replicate are represented in each panel.