Pepsinized Sweet Whey Medium for Growing Lactobacillus acidophilus for Frozen Concentrated Cultures

Abstract

Three pepsinized whey based media were compared for growing cells of Lactobacillus acidophilus NCFM for preparing frozen concentrated cultures. Concentrations of dried sweet whey tested in the media were 2.5, 5.0, and 7.5%. The cells of Lactobacillus acidopbilus NCFM were grown at 37C in various media maintained at pH 6.0 during growth with a neutralizer of 20% sodium carbonate in 20% ammonium hydroxide. As whey solids were increased in the media, maxb mum populations attained during growth decreased. The culture reached maximum populations in the media containing 2.5 and 5.0% whey solids after 12 and 18 h, then remained constant for the remainder of the 24-h incubation period. However, in the medium containing 7.5% whey solids the culture appeared to enter a death phase after only 12 h of incubation. The maximum population in the 7.5% medium was also considerably lower than maximums in the 2.5 and 5.0% media. Concentrated cultures were prepared from cells of Lactobacillus acidopbilus NCFM grown in the media containing 2.5 and 5.0% whey solids and stored in liquid nitrogen. The viability and bile resistance of the cultures during storage in liquid nitrogen and subsequent storage in refrigerated milk was highest for cells of Lactobacillus acidophilus NCFM