Nutritional components and protein quality analysis of genetically modified phytase maize.

The nutritional components and protein quality of genetically modified maize expressing phytase gene (GM) were analyzed and evaluated in this study. The nutritional components were analyzed by Chinese national standard methods. The ileostomy Bama miniature pigs were utilized to analyze the true digestibility of protein and amino acids. The digestible indispensable amino acid score (DIAAS) was adopted to evaluate the protein quality of GM, its parental maize (PM) and commercial available maize Zhengdan 958 (ZD). Meanwhile, the widely used protein digestibility corrected amino acid score (PDCAAS) was also calculated and compared with DIAAS. The content of protein, fat, vitamins, and minerals of all the strains of maize are in the normal ranges of OECD and/or ILSI. The DIAAS of GM, PM, and ZD were 54.57, 31.75, and 33.91, respectively, and the first limiting amino acid for GM, PM, and ZD was lysine. In conclusion, the introduction of phyA2 gene in GM maize does not disturb the digestion of protein/amino acid, but has the ability to promote the digestion of amino acids.