Growth‐promoting factors for Bifidobacterium longum

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Abstract
The ability of various biological materials to promote growth of Bifidobacterium Iongum (ATCC 15708) was tested using Bacto B12 assay medium (Difco Corp.). Supplements included yeast extract, beef extract, malt extract, α‐lactalbumin, β‐lactoglobulin, trypticase soy broth, phytone‐peptone and unknown factors from Escherichia coli spent broth. Growth of B. longum 15708 was monitored by measuring turbidity and pH. Yeast extract, α‐lactalbumin and β‐lactoglobulin were the best growth promoters. Growth in the presence of E. coli spent broth was maximal; however, fresh enzymatically hydrolyzed E. coli broth was as effective. Beef extract and trypticase soy broth were effective to some extent. Malt extract and phytone‐peptone did not significantly enhance growth. All materials lost growth promoting activity when their disulfide bonds were reduced‐alkylated.