Ethanol yields and elevated amino acids in distillers dried grains with solubles from maize grain with higher concentrations of essential amino acids

Concentrations of the essential amino acids, lysine and tryptophan, present in corn distillers dried grains with solubles (DDGS) are insufficient to fully meet the nutritional requirements in non-ruminant feeds. Mutations known to increase lysine and tryptophan concentrations were combined by breeding into two maize hybrid backgrounds that differ for grain protein concentration (FR1064 × Mo17 normal protein, FR1064 × IRHP1 high protein). These mutant hybrids were compared to their non-mutant control isolines for field performance and ethanol and DDGS processing using laboratory scale procedures: conventional dry grind process and modified dry grind process using granular starch hydrolyzing enzyme (GSHE). The mutant hybrid grain contained higher concentrations of a number of amino acids, with notable increases to at least 0.55% w/w lysine and 0.18% w/w tryptophan. Due to lower grain yield and starch concentrations, final ethanol yields of FR1064 × Mo17: o2; asaC28 hybrid were reduced compared to control for both the conventional and modified dry grind processes. However, with the modified process, ethanol yield for FR1064 × IRHP1: o2; asa2-C28 hybrid was similar to its control isoline. DDGS yields increased for both mutant hybrids compared to controls. Although amino acid profiles were similar for DDGS recovered from both the conventional and modified processes, DDGS from the mutant hybrids contained higher concentrations of lysine (1.48–1.70% w/w) and tryptophan (0.32–0.39% w/w) compared to controls (1.09% w/w lysine, 0.22% w/w tryptophan). Using these mutant corn hybrids at an ethanol plant resulted in lower ethanol yields; however, this loss can be recovered with the higher DDGS yield and increased nutritional value of the DDGS.