S.F. Sourdough Yeast and Lactobacillus
I put this out for anyone who might be interested. It describes how to make L. sanfranciscensis and C. humilis, the lactobacillus and yeast in S.F. sourdough. It comes from US patent #3734743 by Kline and Sugihara. I have updated the names of the microorganisms from the patent to reflect the current names.
Is thre anyone with a knowledge of chemistry who could say how feasible this would be to do given a properly-equipped laboratory? Note that these both utilize baker's yeast.
Preparation of pure cultures of the sour dough bacteria L. sanfranciscensis
The bacteria in question grows well on a broth containing the following ingredients:
Sour dough bacteria (SDB) broth
Maltose __________________________________ __ 2
Commercial yeast extract ____________________ __ 0.3
Fresh yeast extractives (FYE)* __________ __ 0.5 to 1.5
'Sorbitan polyoxyethylene monooleate (Tween 80) .. 0.03
Casein hydrolysate (Trypticase) ____________ __ 0.06
Water ____________________________ __ To make 100
*Prepared by autoclaving a 20% suspension of commercial compressed baker's yeast in distilled water for 30 minutes at 15 p.s.i., allowing the suspension to settle overnight at 34—35° R, decanting and further clarifying the supernatant by centrifugation. The extract prepared in this manner contained 1.5% solids and if not to be used within a few days, was frozen or freeze-dried immediately. The FYE preparations are used in a proportion to furnish 0.5 to 1.5% of the dry FYE solids.
Adust to pH 5.6 with 20% lactic acid or acetic acid or1 to 6 N HCl.
The broth is sterilized by autoclaving it, cooled, and inoculated with about 1% of a broth culture of the bacteria, then incubated at about 80° F. for 1 or 2 days.
Since growth of the bacteria is stimulated by CO2, it ispreferably to carry out the culture in an atmosphere containing some CO2. This may be done by ?ushing air out of the top of the culture vessel with CO2 and then stoppering the vessel. Alternatively, the vessel can be placed within a receptacle containing about 25 to 95 volume percent of CO5, (the remainder, air). Alternatively, one may sparge the culture with such gas mixture. During the culture the system is preferably agitated or shaken slowly to get good contact between the growing cells and the nutrients. The bacterial cells are harvested by centrifuging the broth culture, preferably using a refrigerated centrifuge.
The centrifuge cake is then washed with chilled 1% aqueous salt solution to remove nutrients, metabolic products, etc. The washed cells can then be used as the bacterial inoculum for liquid starter make-up.
If the cells are not needed a short time after preparation, they may be preserved as follows:
The washed cells (100‘ parts) are suspended in 200 parts of a stabilizing carrier (a mixture of glycerol and sterile SDB broth) and the suspension is ?ash frozen, using liquid N2 or Dry Ice-acetone slush. The culture is then held in a frozen state (about -20° F. or below),
whereby it retains its viability for at least 2 months. When the product is to be used, it is thawed and used directly.
Further details on preparation of cultures of L. sanfranciscensis are disclosed in our copending application referred to above. Methods whereby this species may be isolated from source materials such as sour dough sponges are also disclosed in said application.
Cultures of several strains of Lactobacillus sanfranciscensis useful for the purpose of the invention have been deposited in the Stock Culture Collection of the US. Department of Agriculture, Northern Regional Research Laboratory, Peoria, Ill.61604, from which organization samples of these strains may be obtained.
Preparation of pure culture of the sour dough yeast Candida Humilis.
The yeast in question grows well on many media, including those used for growing commercial baker’s yeast. We have routinely cultured the organism on the following broth:
Glucose ____________________________________ _. 2
Yeast extract _______________________________ __ 0.5
Casein hydrolysate (Trypticase) _________________ __ 1
Water ________________________________ To make 100
The broth is sterilized by autoclaving it, cooled, and inoculated with about 1% of a broth culture of the yeast, then incubated at about 86° F. for 1 or 2 days under highly aerobic conditions. The yeast cells are harvested by centrifugation or filtration, then washed with chilled 1% aqueous salt solution to remove nutrients, metabolic products, etc. The washed cells can be used directly or stored in the refrigerator for future use. For longer storage, the yeast can be dried — this is preferably done by extruding it through a die to form noodle-like filaments which are dried to a moisture content of about 8% in a current of air at about 100-140°F. To prevent loss of viability, the temperature of the air during the last part of the drying cycle is kept in the lower portion of the stated range, or, alternatively, the humidity of the air stream is increased while keeping the temperature high.
Cultures of several strains of candida humilis useful for the purpose of the invention have been deposited in the Stock Culture Collection of the US. Department of Agriculture, Northern Regional Research Laboratory, Peoria, 111. 61604, from which organization samples of the strains may be obtained. The strains are designated as Nos. NRRL Y-7244, Y-7245, Y-7246, Y-7247, and Y
7248. As noted above, in the sporulating form the yeast may be termed Saccharomyces exiguus.