Probiotic Lactobacillus and Bifidobacterium species are generally fastidious bacteria and require rich media for propagation. In milk-based media, they grow poorly, and nitrogen supplementation is required to produce high bacterial biomass levels. It has been reported that caseinomacropeptide (CMP), a 7-kDa peptide released from κ-casein during renneting or gastric digestion, exhibits some growth-promoting activity for lactobacilli and bifidobacteria. During the digestive process, peptides derived from CMP are detected in the intestinal lumen The aim of this study was to evaluate the effects of peptic and tryptic digests of CMP on probiotic lactic acid bacteria growth in de Man, Rogosa and Sharpe broth (MRS) and in milk during fermentation at 37 °C under anaerobic conditions. The study showed that pepsin-treated CMP used as supplements at 0·5 g/l can promote the growth of probiotics even in peptone-rich environments such as MRS. The effect was strain-dependent and evident for the strains that grow poorly in MRS, with an improvement of >1·5 times (P<0·05) by addition of pepsin-treated CMP. Trypsin-treated CMP was much less efficient as growth promoter. Moreover, pepsin-treated CMP was effective in promoting the growth in milk of all probiotic lactic acid bacteria tested, with biomass levels being improved significantly, by 1·7 to 2·6 times (P<0·05), depending on the strain. Thus, supplementation of MRS and of milk with pepsin-treated CMP would be advantageous for the production of high biomass levels for Bifidobacteria and Lactobacilli.

Serum-free media were used to culture Plasmodium falciparum. A commercial preparation, Daigo's GF21 developed as a growth-promoting factor for many kinds of mammalian cells, and consisting of the 55–70% ammonium sulphate fraction of adult bovine serum, insulin, transferrin, ethanolamine and sodium selenite, was found to sustain growth of the parasite when Daigo's T was employed as a basal medium. The optimal Daigo's GF21 concentration for parasite growth was between 5 and 20% (v/v), with the best results at 10%. Differential counts indicated that Daigo's GF21 is essential for schizogony. Established serum-free medium, GIT, consisting of Daigo's T basal medium and Daigo's GF21, yielded good parasite growth without any supplementation. Growth-promoting factor derived from adult bovine serum in Daigo's GF21 was shown to be crucial to parasite growth. The results presented here will not only be of practical value, but will provide important information about the developmental requirements for the parasite.