A survey of growth stimulators in natural rubber serum powder for Bifidobacterium bifidum

Natural rubber serum powder, rich in crude protein and carbohydrates, had a strong growth-stimulating activity for Bifidobacterium bifidum, which was unable to grow in a fully synthetic medium, B₁₂ assay medium. Natural rubber serum powder was fractionated by ultrafiltration (molecular weight cut off 1000). The active ultrafiltrate was furthermore concentrated and desalted with an adsorptive microconcentrator, which adsorbs virtually all amino acids and peptides. Through this purification step, it was found that the adsorbed fraction obtained could not exhibit a growth-stimulating activity independently but acted complementarily with ammonium sulfate contaminated in the ultrafiltrate. Furthermore, ammonium sulfate could be substituted with other ammonium salts, ammonium chloride and ammonium nitrate. The adsorbed fraction was subsequently analyzed on reversed-phase high performance liquid chromatography, and the activities of the eluates were measured on B₁₂ assay medium supplemented with ammonium sulfate. Consequently, it was proved that several ingredients in the adsorbed fraction enhanced the growth of B. bifidum.