A Study of Cultural Methods for the Quantitative Determination of Bacterial Populations of Distillery Mashes

Abstract

Quantitative cultural data on bacterial contamination in a distillery are difficult to obtain because ordinary methods will not distinguish between yeast and bacteria. Direct counts are unreliable because of the large number of grain particles which are difficult to distinguish from bacteria. This investigation was begun, therefore, in order to find a reliable cultural method for counting bacteria in distillery mashes. A procedure which seemed worthy of investigation was the "tube count" method which has been used for many years by the Bureau of Dairy Industry of the United States Department of Agriculture in counting lactate-fermenting bacteria in Swiss cheese. Dr. W. C. Frazier of the University of Wisconsin suggested that the method had possibilities in routine work, and under his direction it was used extensively in research work on brick cheese (Garey et al., 1941). METHODS Of several special culture media tried, the following medium was found to give satisfactory results:

Metabolism of Glycerol by an Acrolein-Forming Lacto-Bacillus

“…The organism used was lactobacillus strain 208-A, a representative of group H described by 261 on September 21, 2020 by guest http://jb.asm.org/ Downloaded from Serjak et al (1954). The stock culture was maintained in tomato juice agar (Garey et al, 1945). Growth experiments were performed in tomato juice broth or in a defined medium containing the following ingredients, per 1: Glucose or glycerol and glucose as required; casein hydrolyzate (10 per cent casein, acid-hydrolyzed), 150 ml; K2HPO4, 10 g; salts B,' 10 ml; tryptophan, 200 mg; cystine, 200 mg; cysteine, 200 mg; guanine, 12 mg; adenine, 12 mg; uracil, 12 mg; niacin, 2 mg; pantothenic acid, 2 mg; pyridoxal, 2 mg; riboflavin, 2 mg; thiamine, 2 mg; folic acid (Folvite), 1 mg; and Tween 80, 2 g; adjusted to pH 5.7.…”

Malt Sterilization, Cathode Radiation as a Means of Sterilizing Distiller's Barley Malt

“…They were analyzed for -amylase content and residual bacteria and were evaluated as saccharifying agents in laboratory scale grain alcohol fermentations. Lactic acid organisms were determined in shake tubes of tomato juice agar as described by Garey and others (8) and aerobic organisms by plating in nutrient agar. Colony counts were made after 48 hours' incubation at 37°C.…”

“…Grain alcohol fermentations in which barley malt is used for saccharification are subject, as a consequence of bacterial contamination, to the potential development of abnormal acidity, off-flavored distillates, and reduced alcohol yields. Previous reports from this laboratory have been concerned with media and methods for counting these contaminants (mainly Lactobacilli) (8), their general description and the production of acrolein by certain types (74), and the evaluation of antibiotics as contamination-control agents (7).…”

Acrolein Production by Bacteria Found in Distillery Grain Mashes

“…End fermentor samples after proper dilution in sterile water blanks were inoculated into tomato juice agar (TJA) shake cultures as described by Garey et al (1945). The composition of TJA medium was as follows: ....................................... Adjusted to pH 6.9 400 ml 10 g 10 g 5 ml 5 ml 600 ml 15 g Salt solution, A contained 25 g each of mono-and dibasic potassium phosphate per 250 ml of distilled water.…”