SAN FRASCISCO MEDIUM 500 grams/bottle

San Francisco Base Medium Modified is a medium described by Vogel et al. for the identification of Lactobacilli from sourdough in 1994. Picozzi et al. modified this medium by adding 150 ml of a fresh yeast extract solution instead of rye or wheat flour and bakers yeast components since these made the agar plates turbid and spongy. Tryptone and beef extract provide nitrogen, vitamins, minerals and aminoacids essential for growth. Glucose, fructose and maltose are the fermentable carbohydrates providing carbon and energy. Yeast extract is a source of vitamins, particularly of the B-group. Sodium gluconate has been added as a stabilizing agent. Sodium acetate is added as a carbon source. Ammonium citrate at a low pH inhibits most microorganisms, including streptococci and molds, and limits swarming, but allows the growth of lactobacilli. Dipotassium acid phosphate is a buffer. Sulphate salts are ions required in a big variation of enzymatic reactions. L-cysteine hydrochloride is the reducing agent. Bacteriological agar is the solidifying agent.