Wednesday, September 16, 2026

Question: San Francisco sourdough gets its signature tang from a species of lactic acid bacteria so tied to the city that scientists named the microbe after San Francisco. What is it called?

Answer: Lactobacillus sanfranciscensis (recently reclassified as Fructilactobacillus sanfranciscensis). It was first isolated from San Francisco sourdough starters in 1971 by USDA researchers Leo Kline and Frank Sugihara, and produces the lactic and acetic acids behind the tang.