Hydrogen peroxide production in reconstituted skim milk (10%) and low-fat milk by four strains lf Lactobacillus acidophilus was studied at 37 and 4 C. Strains A and B produced little, but strains C and D produced larger amounts, especially if agitated continuously during growth at 37 C or storage at 4 C. Continuous shaking was required at 4 C for C or D (4.0 X 10(8)/ml) to produce sufficient hydrogen peroxide to retard growth of Pseudomonas fragi. Flavin adenine dinucleotide stimulated the oxidation of reduced nicotinamide adenine dinucleotide by dialyzed cell-free extracts of C and D, which indicated that the reduced nicotinamide adenine dinucleotide oxidases of these strains produce hydrogen peroxide as an end product.

The production of lipoprotein lipases by Pseudomonas sp. M-12-33 was improved by an increased aeration. Glucose stimulated the growth of the bacterium but reduced the enzyme production in Bouillon medium. Olive oil remarkably increased the production of lipoprotein lipases but the effect was cancelled by calcium carbonate. Stearic and palmitic acids were as effective as olive oil, but capric and caprylic acids inhibited the enzyme production. Urea was proved to be very effective as '" nitrogen source for the production of lipoprotein lipases.