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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In the process of isolating sialic acid from bovine isoelectric casein a hydrolytic product (CBF) was obtained, possessing growth promoting activity for Bifidobacterium bifidum var. pennsylvanicus. Growth was measured turbidimetrically by addition of CBF (250 ppm) to ATCC Medium 76. Stimulation by CBF was comparable to that obtained with N-acetylglucosamine. Whole casein, sialic acid-free casein and k-casein failed -to stimulate the growth of -the organism to the level achieved with CBI? The CBF fraction contained 0.15% nhosohorus. 7% free lactose and various peptides. No sialic acid or other amino sugars were detected. On the basis of phosphorus content and amino acid analysis it was concluded that CBF was likely a degradation product of k-casein.

Identification techniques for Bacillus cereus are unsettled even though there is an increased awareness of the organism's potential public health implications. Biochemical and morphological characteristics of 17 strains of B. cereus, including 10 isolated from confirmed foodborne outbreaks, were studied by routine methods. Of the characteristics attributed to B. cereus, two strains were negative for the Voges-Proskauer reaction and nitrate reduction; three did not utilize salicin; and five exhibited rhizoidal growth on nutrient agar. Heat resistance of the strains was determined using the serum bottle technique. In demineralized water D- values at 100°C ranged from 0.6 to 27 min, with z-values from 7.4 to 14.5°C. Mean growth constant (k/h) determined turbidimetrically in nutrient broth at 15, 21, 25, 35, 40, 45 and 50°C was 0.15, 0.39, 0.89, 1.54, 1.99, 2.54 and 2.08, respectively. No single feature typified pathogenic strains. At 7 or 11°C, sixteen strains produced hemolysin on blood agar plates, whereas at 45°C, only two strains were hemolytic. Phospholipase activity measured on egg yolk agar plates was evident for three strains at 7°C, for all strains at 35°C, and for only two strains at 45°C.

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A comparison was made of the conventional tube and microplate Limulus amoebocyte lysate assay for detection of gram-negative bacterial lipopolysaccharide in milk. Raw whole milk samples were maintained frozen and portions were examined periodically on alternate days during 13-d storage to evaluate the reproducibility of both Limulus amoebocyte lysate procedures and to determine optimum reaction conditions for the microplate method. One-day-old, raw and locally purchased pasteurized milk samples, held at 7 degrees C, were analyzed during storage to establish the correlation of both procedures with aerobic and modified psychrotrophic plate counts. Vitamin- and mineral-fortified dairy-based products were examined using the microplate Limulus amoebocyte lysate test as a potential indicator of raw material or finished product bacterial quality and possible postprocessing contamination. Statistical analysis of the data collected comparing the conventional tube and the microplate Limulus amoebocyte lysate assay demonstrated no significant difference exists between the methods when either the modified psychrotrophic bacterial count or the aerobic plate count was used to determine gram-negative bacteria in pasteurized or raw milk (P less than .91). The microplate method, which uses half the lysate reagent, was a good indicator of the bacterial quality of milk and fortified dairy products, consistently detecting bacterial levels greater than 10(3) to 10(4)/ml.

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Germination, growth, sporulation, and. survival of Bacillus cereus 7 was determined in cultured (Streptococcus lactis C10) and direct acidified (lactic acid) skimmilks. For cultured systems, B. cereus increased initially at approximately the same rate in milks with or without streptococci. However, as the acidity of the milk increased, vegetative B. cereus cells failed to survive but spore counts remained unchanged. B. cereus organisms did not influence acid production or multiplication of the lactic streptococci. In direct acidified skimmilk, spore germination and outgrowth and vegetative cell multiplication decreased as the pH of the system was lowered from 6.5 to 5.0. In skimmilk at pH 5.0, vegetative cells failed to multiply and spore germination ceased. In Cheddar cheese manufacture, B. cereus multiplied rapidly during the period from the end of cooking to milling of the curd. B. cereus survived in the spore state in Cheddar cheese during 52 weeks curing.