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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Vikram V. Mistry


Bifidobacteria, Infant formulas, Growth characteristics, Growth promoters, Lactulose, Fructooligosaccharides


Four strains of bifidobacteria; B. bifidum (ATCC 15696), B. longum (ATCC 15708), B. breve (ATCC 15700), and B. infantis (ATCC 15697) were rehydrated in MRS broth and inoculated at 2.5% into three types of infant formula: soy-based (SB), milk-based (MB), casein-hydrolyzed (CH), and control, non fat milk (C) followed by incubation at 37°C for 24 h. Mean maximum colony forming unit per milliliter (cfu/ml) for B. bifidum were 6.lxl06 (SB), 1.4xl09 (MB), l.lxl07 (CH), and l.8xl09 (C). Generation time (G) ranged from 96 (MB) to 322 (SB) min. Mean maximum bacterial counts for B. longum were 2.6xl08 (SB), 2.2xl08 (MB), 5.9xl07 (CH), and l.3xl09 (C) cfu/ml. Generation times ranged from 121 (C) to 337 (CH) min. For B. breve maximum counts were l.2xl09 (SB), 2.3xl09 (MB), 2.5xl08 (CH), and 2.7xl09 (C) cfu/ml and G ranged from 88 (MB) to 220 (CH) min. The mean maximum counts for B. infantis were 2.4xl08 (SB), 3.7xl08 (MB) 6.8xl07 (CH), and 8.lxl08 (C) cfu/ml with G ranging from 64 (MB) to 120 (CH) min. Counts for SB and MB were similar (P> .05) with all strains except B. bifidum and those for CH were always the lowest (P< .05) for all strains except B. bifidum for which SB had the lowest maximum count. Generation times for B. longum and B. breve indicated similar (P> .05) trends. Results suggest that growth characteristics of bifidobacteria in infant formula were strain specific and that maximum growth occurred in milk-based formula. In another experiment growth promoters, lactulose and fructooligosaccharides (FOS), were inoculated at .5% into SB and CH with 2.5% of above mentioned 4 strains of bifidobacteria and their mixture (mixed-culture), and incubated at 37°C for 24 h. Lactulose did not influence maximum counts and G in SB and CH for all the strains except B. infantis for which counts were lower (P < .05) in CH. Trends of developed acidity and pH in SB and CH with or without lactulose for mixed-culture similar (P > .05) to that for B. breve. Maximum counts and G remained unchanged (P > .05) in SB and CH with or without FOS for all the strains and mixed-culture except B. bifidum in SB for which maximum counts did not occur. Growth in SB and CH was inhibited (P < .05) for B. infantis with lactulose and B. breve with FOS past 8 h inoculation suggesting that lactulose and FOS were not an alternative to enhance the growth of bifidobacteria in vitro in infant formulas.

Library of Congress Subject Headings

Infant formulas -- Health aspects
Bifidobacterium -- Growth


Includes bibliographical references (pages 45-60)



Number of Pages



South Dakota State University


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