Acidolin was isolated from skimmilk cultured for 48 hours with Lactobacillus acidophilus (CHR. HANSEN's Laboratory strain 2181). It was extracted from the skimmilk with methanol and acetone and was further concentrated and purified by Sephadex G-25 gel filtration, high voltage electrophoresis, and thin-layer chromatography on silica gel. Ultraviolet, infrared, nuclear magnetic resonance, and mass spectra results are presented for the antibiotic. Acidolin has a low molecular weight (-200), is acidic in nature, possesses a yellow-brown color, and is highly hygroscopic and thermostable. Acidolin exhibits antimicrobial activity against enteropathogenic organisms and sporeformers and only limited activity against lactic-acid bacteria. It is non-toxic to tissue culture cells (H-Ep-2) and is more active against vaccinia than polio virus. The production of antibiotics by lactobacilli has been reported by several workers: KODAMA2) * Approved as Journal Series Article 3-74 of the Ohio Agricultural Research and Development Center.

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The effect of 0.05 and 0.10% potassium sorbate on acid and acetaldehyde production and growth of three commercial yogurt cultures was studied. Either amount of potassium sorbate retarded growth of both Lactobacillus bulgaricus and Streptococcus thermophilus strains in the commercial cultures and also decreased the rate of acid production of cultures incubated at 45 C. Acetaldehyde in these cultures decreased during storage and decreased more in samples containing potassium sorbate. In all trials 0.1% potassium sorbate had a greater effect than 0.05% on the above characteristics of the yogurt cultures.