Nutritive value of processed Saccharomyces cerevisiae, Scenedesmus obliquus and Spirulina platensis as measured by protein synthesis in vitro in rat skeletal muscle

Abstract

Rats were fed for six consecutivedaysonadiet containingtheproteinsourcesunder test at a protein level of 20%. Protein synthesis by skeletal muscle ribosomes was measured in vitro. Synthetic activity was estimated per unit ribosomal RNA and per g of wet weight of muscle. In separate experiments the nitrogen efficiency ratio (n.e.r.) of the protein sources was determined after 21 days feeding at a 10% protein level.As measured by protein synthesis the nutritional quality of lyophilised baker's yeast Saccharomyces cerevisiae increased after mechanical disintegration. A further improvement was achieved by feeding yeast protein concentrates.Judged by these determinations the nutritional quality of the three yeast preparations was higher than that of the low-quality protein, wheat gluten but did not reach the level of the high-quality protein, casein supplemented with methionine.The metabolic utilisation of spray-dried microalga Scenedesmus obliquus increased after mechanical disintegration from a value similar to that of wheat gluten to the level of methionine-supplemented casein.Lyophilised Spirulina platensis had a nutritional quality between that of wheat gluten and casein supplemented with methionine. Addition of the limiting amino acid methionine to air-dried baker's yeast or drum-dried Scenedesmus obliquus and Spirulina platensis stimulated the metabolic utilisation of the micro-organisms.Supplementation of the diet with methionine increased the nitrogen efficiency ratio of air-dried yeast and of drum-dried Scenedesmus obliquus but had no effect on drum-dried Spirulina platensis. The ratios were significantly lower than those of casein supplemented with methionine.There was no difference in the nitrogen efficiency ratio between disintegrated yeast and yeast protein concentrate but the ratio of both was higher than that obtained with lyophilised yeast. The ratio was similar to that of casein without the addition of methionine.

Dietary amino acids: effect of depletion and recovery on synthesis in vitro in rat skeletal muscle and liver

“…It has been shown previously (von der Decken, 1967(von der Decken, , 1968(von der Decken, , 1969; von der Decken & Omstedt, 1970; Omstedt & von der Decken, 1972) that protein synthesis in skeletal muscle and in liver is increased after feeding with proteins during I d subsequent to 3 or 5 d of protein starvation. Refeeding with an adequate-protein diet after 12 weeks of protein restriction caused a partial recovery from hepatic lesions within 48 h (Enwonwu & Sreebny, 1971).…”

“…There is a significant reduction in the protein turnover after giving rats a low-protein diet (Waterlow & Stephen, 1968). The ability of ribosomes to incorporate amino acids into protein in vitro is correlated with the biological value of the nitrogen sources (von der Decken & Omstedt, 1970, 1972Omstedt & von der Decken, 1972;Omstedt, von der Decken, Hedenskog & Mogren, 1973). In the present investigation dietary proteins were replaced by defined amino acid mixtures, which have the advantage that changes in their composition are easily made to suit the purpose of the investigation.…”

Effect of Dietary Protein and Amino Acid Mixture on Protein Synthesis <i>in vitro </i>in Rat Liver

“…The microalgae Scenedesmus obiiquus and Spiruiina piatensis were obtained from the Kohlenstoffbiologische Forschungsstation EV Dortmund (FRG).3. Details on conditions of cul ture and processing have been described previously [12], The composition of the complete amino acid mixture was that of whole egg [13]. When one amino acid was excluded, the corresponding amount of nitrogen was added in the form of glycine.…”

“…Investigations dealing with intracellular protein metabolism have revealed that the activity level of protein synthesis in liver and skeletal muscle is deter mined by the quality of the dietary proteins [3][4][5][6][7][11][12][13]. In skeletal muscle, a positive correlation was obtained between the biological value of the dietary proteins and protein synthesis; but there can be discrepancies between protein synthesis and protein efficiency ratio determinations [7,12].…”

“…In skeletal muscle, a positive correlation was obtained between the biological value of the dietary proteins and protein synthesis; but there can be discrepancies between protein synthesis and protein efficiency ratio determinations [7,12].…”