Amino Acid Balance is Affected by Protein Concentration in Soybean

Abstract

Soybean [Glycine max (L.) Merr.] produces a high‐quality protein that provides an appropriate balance of amino acids for monogastric animals. It has been reported that the relative abundance of some essential amino acids may be reduced in soybean with high protein concentration. A dilution of essential amino acids in soybean protein would lead to a reduction in the value of that protein to the end user, and undefined variation in amino acid balance of soybean would lead to poorly balanced animal rations. The objective of this work was to determine whether amino acid balance is affected by seed protein concentration and to characterize any putative changes in the relative abundance of each amino acid across a range of soybean protein concentrations. We created a wide range of protein concentrations in soybean seed by imposing managed stress treatments previously shown to lower or raise protein concentration. We found that the amino acid composition of soybean protein was affected by protein concentration. The relative abundance of amino acids that are often limiting for animal growth, such as lysine, methionine, cysteine, tryptophan, and threonine, were reduced with increasing seed protein concentrations, whereas arginine and glutamic acid were increased. However, treatments used in this study uncovered a potential role for the availability and source of reduced C and N to impact the relative abundance of each amino acid independently, highlighting the complexity of this interrelationship.

Soybean yield, biological N2 fixation and seed composition responses to additional inoculation in the United States

“…8 and Pfarr et al . 29 reported that most of the EAAs decreased as protein concentration increased, while glutamic acid and arginine increased in relative abundance. Our results showed that increases in protein produce a more than proportional increase in cysteine and close to a proportional increase in methionine, showing that increases in protein would partially overcome the low concentration of these deficient AAs.…”

Historical trend on seed amino acid concentration does not follow protein changes in soybeans

“…4 ). Using protein as a predictor of the AA changes over time was previously reported 9 , but considering only modern genotypes rather than a historical set as presented in this current study. Our findings show similar relationships for some AA changes such as glutamic acid and arginine relative-to-protein genetic gain (Fig.…”

“…The relationship between seed protein and AA concentration varies according to each AA. For instance, lysine, methionine, cysteine, tryptophan, and threonine are negatively correlated with seed protein concentration, whereas arginine and glutamic acid increase with seed protein concentration 9 , 13 . In China, significant negative trends for glutamic acid, histidine, and arginine were reported in soybean genotypes released between 1923 and 2007 14 .…”

“…Average protein concentration in current commercially available soybean genotypes ranges between 33 and 39% (on 130 g kg −1 moisture content) 8 . Commonly, 18 AAs (essential and non-essential) are reported as soybeans protein constituents 9 . Asparagine and glutamine are the most abundant, corresponding to approximately 12% and 18%, respectively, of total AAs; however, they are considered non-essential for humans and monogastric animals 10 .…”

Soybean Amino Acids in Health, Genetics, and Evaluation

“…It has long been recommended that protein quality is based upon essential amino acid content. However, for many reasons, animal feed and human food markets have only recently begun assessing accordingly [5,18,19]. Equipment required for accurate amino acid measurement and the diversity of markets for amino acids makes it difficult for supply chain evaluators like elevator operators to appraise amino acid content on site.…”