No abstract

Management of dairy whey has often involved implementation of the most economical disposal methods, including discharge into waterways and onto fields or simple processing into low value commodity powders. These methods have been, and continue to be, restricted by environmental regulations and the cyclical variations in price associated with commodity products. In any modern regimen for whey management, the focus must therefore be on maximizing the value of available whey solids through greater and more varied utilization of the whey components. The whey protein constituents offer tremendous opportunities. Although whey represents a rich source of proteins with diverse food properties for nutritional, biological, and functional applications, commercial exploitation of these proteins has not been widespread because of a restricted applications base, a lack of viable industrial technologies for protein fractionation, and inconsistency in product quality. These shortcomings are being addressed through the development of novel and commercially relevant whey processing technologies, the preparation of new whey protein fractions, and the exploitation of the properties of these fractions in food and in nontraditional applications. Examples include the following developments: 1) whey proteins as physiologically functional food ingredients, 2) alpha-lactalbumin and beta-lactoglobulin as nutritional and specialized physically functional food ingredients, and 3) minor protein components as specialized food ingredients and an important biotechnological reagents. Specific examples include the isolation and utilization of lactoferrin and the replacement of fetal bovine serum in tissue cell culture applications with a growth factor extract isolated from whey.

No abstract

We have investigated the response of several epithelial and fibroblastic cells to a mitogenic extract of bovine milk. Cation exchange chromatography was used to produce a mitogen-rich fraction from an industrial whey source that, although comprising only 0.5% of total whey protein, contained the bulk of the growth factor activity. This fraction was a source of potent growth promoting activity for all mesodermal-derived cells tested, including human skin and embryonic lung fibroblasts, Balb/c 3T3 fibroblasts, and rat L6 myoblasts. Maximal growth of all these cell types exceeded that observed in 10% fetal bovine serum. Feline kidney and baby hamster fibroblasts and Chinese hamster ovary cells were less responsive, achieving a maximal growth response of 50-75% that observed in 10% fetal bovine serum. Maximal growth achieved in whey-extract-supplemented cultures of Balb/c 3T3 and human skin fibroblasts, and L6 myoblast cultures exceeded that seen in response to recombinant acidic or basic fibroblast growth factor, platelet-derived growth factor, insulin-like growth factor, or epidermal growth factor. Importantly, addition of low concentrations of fetal bovine serum to the whey-derived mitogenic fraction produced an additive response. However, concentrated milk-derived factors were found to be inhibitory to the growth of all epithelial lines tested, including rat intestinal epithelial cells, canine kidney epithelial cells, and mink lung cells. It is concluded that industrial whey extracted in this form constitutes an important source of potent growth-promoting agents for the supplementation of mesodermal-derived cell cultures.

Bovine cheese whey was investigated as a source of growth-stimulating factors that might replace or supplement fetal bovine serum in cell culture. Although some cell growth activity was demonstrated in whey or whey ultrafiltrates, enrichment on the basis of molecular size was not useful because the most abundant whey proteins, beta-lactoglobulin and alpha-lactalbumin, have molecular masses that are similar to most known growth factors. Instead, cation-exchange chromatography was selected as an enrichment process because, in contrast to the major whey proteins, growth factors generally have basic isoelectric points. Adsorption to and elution from Sepharose Fast Flow-S resin yielded an extract containing only 1 to 2% of whey protein but substantial growth-promoting activities on Balb/c 3T3 cells, L6 myoblasts, and human skin fibroblasts. The growth activity could be separated from lactoferrin, one of the prominent basic proteins present, through a stepwise elution from the resin. The resultant fraction, which contained lactoperoxidase as the most abundant protein stimulated the growth of the three cell lines at protein concentrations that were 2- to 20-fold lower than observed with fetal bovine serum. Immunoglobulin G could be removed by affinity chromatography, or lactoperoxidase could be inactivated by heat, without significant losses to the growth-promoting capacity of the fraction. These results suggest that enrichment of growth factors by cation-exchange chromatography offers a practical method for the large-scale isolation of an extract from cheese whey that stimulates cell growth.