Identification of a Growth Stimulant for Lactobacillus sanfranciscot

The starter sponge, or inoculum, used in the production of San Francisco sourdough French bread contains a unique heterofermentative Lactobacillus species that was first isolated by Kline and Sugihara (4). Based on the exacting nutritional requirements and genetic composition of this organism, these authors proposed the new species name Lactobacillus sanfrancisco for the sourdough bacterium. Successful isolation of this organism requires the incorporation of a hot-water extract of bakers' yeast into artificial culture media. This nutritional requirement cannot be fully met by commercial yeast extracts or various other crude complex extracts of plant and animal origin (9). The present study was initiated to isolate and identify the component(s) of fresh yeast extract (FYE) responsible for the stimulation of L. sanfrancisco.