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The Cultivation, Growth, and Viability of Lactic Acid Bacteria: A Quality Control Perspective
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Recovery of Lactic Acid Bacteria on Petrifilm™ SM Under Various Incubation Atmospheres 1
John U McGREGOR1, Sandra M Traylor1, Ronald H Gough1
1Dairy Science Department, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803.
Abstract:
The ability of lactic cultures to grow on Petrifilm™ SM plates was studied. Frozen yogurt mix was analyzed microbiologically by plating on TOE, LBS, M17 and Petrifilm™ SM. Plates were incubated aerobically in a Gas-Pak System and under a CO2 environment. Also, Lactobacillus bulgaricus , Streptococcus thermophilus , Lactococcus lactis subsp. diacetylactis , and Leuconostoc cremoris were isolated from yogurt and buttermilk samples for study. Isolated cultures were grown in nutrient broth and plated on Petrifilm™ SM and M17 agar. Plates were incubated aerobically and in a Gas-Pak system. Petrifilm™ SM plates performed as well or better than the M17 agar in assaying lactic growth with the exception of Streptococcus thermophilus culture in an aerobic environment. Petrifilm™ SM plates show promise as a method for enumerating viable lactic cultures if incubated in a reduced oxygen environment.
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