71A-25 |
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M. M. SALAMEH, S. A. Ibrahim, C. W. Seo, and S. A. Ahmad. Food Science and Nutrition Program, North Carolina A&T State Univ., Dept. of Human Environment and Family Sciences, 171-B Carver Hall, Greensboro, NC 27411-1064 The International Dairy Federation (IDF) recommends M17 broth for starter lactococci and streptococci and MRS broth (DeMan Rogosa Sharpe) for starter lactobacilli growth. An M17 broth medium with specific modifications could be utilized for growth of selected Lactobacillus reuteri and Bifidobacterium sp. as a convenient medium that can be used easily by the industry in a routine fashion. The objective of this study was to evaluate the ability of modified M17 to promote the growth of L. reuteri and bifidobacteria. Six strains of L. reuteri (DSM20016, MM2-3, SD2112, CF2-7F, and MF14-C) and four strains of Bifidobacterium sp. [B. infantis (ATCC 15697, ATCC 15702, ATCC 25962), and B. longum 79] were used in this study. The modified M17 broth was prepared by adding M17 37.25 g/l; beef extract 5.0 g/l, yeast extract 2.5g/l, and peptone from casein 5.0 g/l. Glucose solution (20.0g/100ml) was autoclaved separately and added to the sterilized modified M17 broth. Overnight cultures were centrifuged and washed twice with peptone water. Strains were then inoculated into fresh M17 and modified M17 broths, then mixed well and incubated at 37 °C for 24 hr. Bacterial growth was monitored using a spectrophotometer 21 (610nm) at 0.0, 12, and 24 hr. At the end of the incubation period, all tested strains were plated on MRS agar to obtain microbial population. Results showed that higher microbial growth was observed in all tested strains using modified M17. The optical density in the modified M17 reached 1.30 and greater, while it only reached 0.70 in the original M17. The bacterial population increased by at least 1.0 log cfu/ml. Results suggest that modified M17 broth could be a good growth medium in quality control laboratories for the general purpose of bacterial growth of lactic acid bacteria and probiotics.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |