In addition to oligosaccharides and carbohydrates, other biologically complex
materials such as bovine casein digest, yeast extract, amino sugars, and peptides
have been examined in efforts to improve the growth of bifidobacteria. Poch
and Bezkorovainy demonstrated that yeast extract and bovine casein digest promoted
the growth of bifidobacteria in TPY media.113 Klaver et al. reported that 15 out of 17
Bifidobacterium strains tested grew poorly in milk, which was attributed to lack of
proteolytic activity in these strains, whereas addition of casitone (casein hydrolysate)
or a mixture of amino acids to the milk-based medium resulted in good growth of
most of the strains.108 Another approach has involved the coculturing of proteolytic
species, such as lactobacilli with bifidobacteria, which has resulted in the enhanced
availability of sufficient nitrogenous compounds, leading to improved growth of bifidobacteria
in milk.108 For example, B. lactis demonstrated enhanced growth when
co-cultured with Lb. acidophilus in milk.116 Bifidobacteria species have also shown
variable growth in media, as studies by Desjardins et al. have indicated that bifidobacteria
of infant origin grow much better in milk than those of adult origin;115
further, Poch and Bezkorovainy indicated that bifidobacteria species of infant origin
grow better than those of adult origin in the presence of growth factors