''Fructilactobacillus sanfranciscensis'' is a heterofermentative species of lactic acid bacteria which, through the production mainly of lactic and acetic acids, helps give

sourdough bread Sourdough or sourdough bread is a bread made by the fermentation of dough using wild lactobacillaceae and yeast. Lactic acid from fermentation imparts a sour taste and improves keeping qualities. History In the ''Encyclopedia of Food Microbiolo ...

its characteristic taste. It is named after

San Francisco San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...

, where sourdough was found to contain the variety, though it is dominant in Type I sourdoughs globally. In fact, ''F. sanfranciscensis'' has been used in sourdough breads for thousands of years, and is used in 3 million tons of sourdough goods yearly.

Sourdough starter Sourdough or sourdough bread is a bread made by the fermentation of dough using wild lactobacillaceae and yeast. Lactic acid from fermentation imparts a sour taste and improves keeping qualities. History In the ''Encyclopedia of Food Microbio ...

s are

leaven In cooking, a leavening agent () or raising agent, also called a leaven () or leavener, is any one of a number of substances used in doughs and batters that cause a foaming action (gas bubbles) that lightens and softens the mixture. An alterna ...

ed by a mixture of

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

and lactobacilli in a ratio of about 1:100. The yeast is most commonly ''Kasachstania humilis'' (formerly ''

Candida humilis ''Candida humilis'' is a species of yeast in the genus '' Candida''. It commonly occurs in sourdough and kefir cultures, along with different species of lactic acid bacteria (e.g., ''Lactobacillus fermentum'', '' Lactobacillus paralimentarius'', ...

'' or ''C. milleri)''. This yeast cannot metabolize the

maltose } Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two- ...

found in the dough, while the ''Fructilactobacillus'' requires maltose. They therefore act without conflict for substrate, with lactobacilli utilizing maltose and the yeast utilizing the other sugars, including the glucose produced by the ''F. sanfranciscensis''. External conditions such as acidity and temperature affect the growth rates of ''F. sanfranciscensis''. A temperature of 33 °C (91 °F) leads to maximum growth rates, whereas temperatures over 41 °C (105 °F) completely inhibit the bacteria growth. Ideal and maximum growth temperatures of other organisms may be quite different; for instance a common yeast in sourdough, ''K. humilis'' prefers 27 °C (81 °F) and will not grow above 36 °C (97 °F). For commercial use, specific strains of ''F sanfranciscensis'' are grown on

defined media A definition is a statement of the meaning of a term (a word, phrase, or other set of symbols). Definitions can be classified into two large categories: intensional definitions (which try to give the sense of a term), and extensional definitio ...

, freeze-dried, and shipped to bakeries worldwide.

References

External links

Type strain of ''Lactobacillus sanfranciscensis'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q1757333 History of San Francisco Lactobacillaceae Bacteria described in 1971 Cuisine of the San Francisco Bay Area