Metabolism of milk fat globule membrane components by nonstarter lactic acid bacteria isolated from cheese

The objective of this study was to investigate how components present in the milk fat globule membrane (MFGM) may be used for growth and survival by cheese-ripening lactobacilli. This was achieved by analyzing metabolites produced during incubation on appropriate media. The lactobacilli investigated were able to utilize components from the MFGM throughout a 24-d incubation period. We observed an apparent connection between the higher proteolytic activity of Lactobacillus paracasei INF448 and its ability to grow in the MFGM media after depletion of readily available sugars. All the studied strains produced large amounts of acetate when grown on an acylated aminosugar, presumably from deacetylation of the monosaccharides. Growth of Lb. plantarum INF15D on D-galactose resulted in a metabolic shift, expressed as different fates of the produced pyruvate, compared with growth on the other monosaccharides. For Lb. plantarum INF15D, the presence of D-galactose also seemed to initiate degradation of some amino acids known to take part in energy production, specifically Arg and Tyr.