Protein, peptide, amino acid composition, and potential functional properties of existing and novel dietary protein sources for monogastrics

Replacement of current protein resources for novel or alternative sources may be one of the solutions to abolish the expected scarcity of dietary protein for animal feeds. However, little is known about the nutritional, protein composition, and potential functional value of such novel or alternative protein sources. In the present study, we used advanced proteomic and bioinformatic approaches to characterize the protein component of 6 different protein sources and predicted the biofunctionalities of their in vivo digestion products. We used casein (CAS), partially delactosed whey powder (DWP), spray-dried porcine plasma (SDPP), soybean meal (SBM), wheat gluten meal (WGM), and yellow meal worm (YMW). We characterized and semiquantified the individual proteins present in these resources by nano-liquid chromatography-LTQ Orbitrap-mass spectrometry (nLCMS). Based on the data obtained, we calculated the AA composition of the proteins that constitute 90% of the total calculated protein content and compared this with the chemically deter- mined AA compositions of the corresponding protein sources. By the use of bioinformatic procedures, we predicted the bioactive properties of these protein sources after in silico digestion with monogastric proteolytic enzymes. We detected and semiquantified 37, 58, 85, 188, 113, and 33 different individual proteins in CAS, DWP, SDPP, SBM, WGM, and YMW, respectively. The calculated AA composition of the various protein sources was almost identical to the chemically determined composition, with correlation values ranging from 0.85 to 0.94. Furthermore, we revealed that the selected protein sources are potentially rich in bioactive peptides, in particular of angiotensin-converting enzyme inhibitors and peptides with antioxidative properties. We discuss the results in terms of the benefit of the applied nLCMS-based approach for analyzing protein feed ingredients and the use of these alternative sources of protein in animal feeds for monogastrics. Furthermore, we discuss new potential applications of this method in the area of (animal) nutrition.