What role does Lactobacillus play in brewing?

Lactobacillus plays a crucial role in brewing, specifically in the production of tart lactic acid. This bacteria is a primary player in sour beer production because it can convert sugars into lactic acid. This bioconversion not only contributes to the sour and tangy flavor profile associated with sour beers but also influences the beer's overall acidity and mouthfeel. The presence of lactic acid gives these beers their distinctive character, differentiating them from traditional styles that focus on cleaner, crisper profiles.

In terms of the other functions mentioned, Lactobacillus does not produce bitterness, ferment sugars into ethanol, or generate significant amounts of carbon dioxide like other fermentation yeasts. While there are elements of fermentation in brewing, the specific contribution of Lactobacillus to the flavor profile of sour beers through lactic acid production is what makes this answer the most relevant and accurate.