Biological Evaluation of Thaumatococcus danielli Waste Protein

The impact of laboratory chow for rats in the experiments: Chemical and biological evaluation of nine grain-based diet options

Cereal-based diets formulated as semi-purified diets can provide flexibility for researchers, enabling open controlled formulas, besides being cheaper than purified diets. Seeking to widen the researchers’ options in their experimental design developments, we aimed at assaying the chemical score, growth performance and protein utilization of nine semi-purified experimental chows. These diets were formulated at 17.8%, 12% and 8% protein contents, using three variations of ingredients for each one, as follows: casein (C), casein+soybean meal (C+S, 1:1 w/w protein) and casein+soybean meal+corn gluten meal (C+S+G, 1:1:1 w/w protein), without cysteine supplementation and setting casein 17.8% (AIN-93G) as reference diet. The diets C and C+S (17.8%) had the Cys as the limiting amino acid once the addition of gluten turns the Lys as second limiting. All diets had the potential for promoting growth with body mass gain, feed conversion ratio (FCR; chow consumed per body weight gain, average 3.12) and feed efficiency ratio (FER; body weight gain per chow consumed, average 0.3), except for C+S+G 8% (FCR = 6 g; FER = 0.13). These variations were mainly due to the protein amounts independently from the protein ingredient used and could characterize the C+S+G 8% as unable to support growth. For the other parameters (digestibility, net protein ratio, net protein utilization and protein efficiency ratio), there were no relevant differences between the diets. We can conclude that 17.8%, 12% and 8% chows (C and C+S) allowed a proper combination of ingredients from the point of view of palatability, nutrient availability/utilization, metabolic processes, growth performance and feed utilization parameters.

Chemical composition and biological value of proteins of the yeast Yarrowia lipolytica growing on industrial glycerol

Michalik, B., Biel, W., Lubowicki, R. and Jacyno, E. 2014. Chemical composition and biological value of proteins of the yeast Yarrowia lipolytica growing on industrial glycerol. Can. J. Anim. Sci. 94: 99–104. The aim of this study was to evaluate the chemical composition and biological value of proteins from the yeast, Yarrowia lipolytica, after cultivation on glycerol, a waste product obtained in the production of biofuel from rapeseed. In the tested material we determined moisture, crude protein, ether extract, nitrogen-free extract (NFE), ash, calcium, phosphorus, cadmium, mercury, arsenic, amino acids and fatty acids. The biological value of Y. lipolytica and Saccharomyces cerevisiae proteins was determined with laboratory rats by two methods: the growth method (protein efficiency ratio standardized for casein, PERstand; net protein retention, NPR) and the Thomas–Mitchell method (biological value, BV; true digestibility, TD). The protein content of Y. lipolytica [467 g kg−1 dry matter (DM)] was similar to that of S. cerevisiae (479 g kg−1 DM). Of particular interest was the almost 30-times higher crude fat content in Y. lipolytica (200 g kg−1 DM) than in S. cerevisiae (6.7 g kg−1 DM). Yarrowica lipolytica cells accumulated substantial amount of fat in which more than 90% of fatty acids were unsaturated fatty acids with a considerable share of polyunsaturated fatty acids (34%). The low share of sulfur amino acid of Y. lipolytica (2.05 g 16g−1 N) and S. cerevisiae (2.32 g 16g−1 N) limited the nutritional value of the protein of the studied yeast. The biological value of proteins as assessed by the growth method (PER, NPR) did not differ between the two yeast species. Finally, Y. lipolytica was a rich source of highly digestible ether extract (over 57%).