Nutritional assessment of transgenic lysine‐rich maize compared with conventional quality protein maize

BACKGROUND: The gene sb401 encoding a lysine‐rich protein has been successfully integrated into the genome of maize (Zea mays), its expression showing as increased levels of lysine and total protein in maize seeds. As part of a nutritional assessment of transgenic maize, nutritional composition, especially unintended changes in key nutrients such as proximates, amino acids, minerals and vitamins as well as in antinutrient (phytate phosphorus), and protein nutritional quality were compared between transgenic maize (inbred line 642 and hybrid line Y642) and conventional quality protein maize (QPM) Nongda 108. RESULTS: The contents of total protein, lysine, some other amino acids, several minerals and vitamin B₂ in transgenic inbred line 642 and hybrid line Y642 were significantly higher than those in conventional QPM. Water‐soluble protein and G2‐glutelin were significantly promoted in transgenic maize Y642. CONCLUSION: Insertion of the lysine‐rich sb401 gene increased the total protein and lysine content of transgenic maize varieties, leading to an improved amino acid score and therefore an improvement in the nutritive value of maize. © 2013 Society of Chemical Industry     

RNAi沉默淀粉分支酶sbe3基因对水稻直链淀粉的影响

本研究利用RNAi技术,通过RT-PCR方法克隆出水稻淀粉分支酶sbe3基因片断,经两步组装法将sbe3基因片断分别正向、反向组装入pRNAi-ubi,成功构建sbe3基因RNAi转化载体pRNAi-ubi/sbe3。在农杆菌介导下,对粳稻中花11未成熟胚诱导的愈伤组织进行转化,通过PCR、Southern杂交鉴定获得一批转基因植株。半定量RT-PCR鉴定出转化苗T1代种子中sbe3基因表达被明显抑制,但只引起转基因水稻胚乳中直链淀粉含量少量的提高,说明采用RNAi仅沉默sbe3基因对水稻胚乳直链淀粉含量没有显著影响。     

Assessment of protein nutritional quality and effects of traditional processes: a comparison between Ethiopian quality protein maize and five Ethiopian adapted normal maize cultivars

The present study was designed to quantitatively measure and compare the levels and variations of total protein, individual amino acids, and computed protein efficiency ratio (C-PER) in raw and traditionally processed products of one recently released quality protein maize (QPM BH542) with four high-yield maize hybrids, namely flint BH660, semi-dent BH140, Pioneer 30H83, and Pioneer 30G97, as well as one local maize cultivar. The total protein content was variable among the cultivars ranging from 7% for BH660 to 8.6% for Pioneer 30H83, 8.9% for BH140, 9.8% for QPM BH542, 10.1% for local maize cultivar, and 11.8% for Pioneer 30G97, respectively. However, the QPM BH542 maize protein proved to be higher in nutritional quality than common maize proteins because it contained 30% to 82% more lysine, higher levels of arginine, tryptophan, histidine, threonine, cysteine, and valine. As a result, the QPM BH542 amino acid profile gives a good balance of total essential amino acids, limited only in lysine, and has a C-PER ratio of 2.2 compared to 1.14, 1.2, 1.4, 1.66, and 1.67 for Pioneer 30G97, local, BH-140, BH660, and Pioneer 30H83, respectively. The various traditional processes of maize have no significant effect on the protein nutritional quality of the new quality protein maize. Hence, the widely dissemination of it in agricultural cultivation as well as consumption by the general population is recommended.     

A new candidate protein for high lysine content in wheat grain

Lysine is the most limiting essential amino acid in cereal grains, so that grain lysine content is important for human nutrition and livestock growth. Translation elongation factor 1α (EF‐1α) from cereal embryo was recently reported to be rich in lysine, and the possibility of using this protein as a marker for feed quality was explored in maize. In this study we used immunochemical methods to investigate the relationship between the content of EF‐1α and other proteins from wheat germ and lysine content in both hexaploid (bread) wheats and diploid wheat progenitors to the wheat A‐genome. The levels of grain lysine, as well as their variation between lines or cultivars, were greater for the diploid wheats. While there was a significant correlation between the levels of EF‐1α and grain lysine content, the binding of antibodies to a protein of M_r 37 000 showed a higher correlation. This protein was characterised by amino acid sequencing as fructose 1,6‐bisphosphate aldolase. The possibility of using fructose 1,6‐bisphosphate aldolase as a marker for feed quality and development of a simple ELISA for quantification of lysine in wheat is demonstrated. © 2000 Society of Chemical Industry     

Proteins of Italian millet: Amino acid composition,solubility fractionation and electrophoresis of protein fractions

Determination of the protein contents of 14 varieties of Italian millet revealed considerable varietal differences. The total protein of the 14 varieties was fractionated into albumin-globulin, prolamin and glutelin fractions. The prolamin fraction constitutes the major storage protein of the grain. There is a positive correlation between protein content and the prolamin levels of the seeds and the increase in protein content is largely due to an increase in the prolamin content. The amino acid composition of each of 14 varieties of the millet and the individual protein fractions from three varieties were determined. The limiting amino acids are lysine followed by tryptophan and the sulphur containing amino acids, methionine and cystine. The lysine content of the grain decreases with increase in protein content. The total protein has a rather high content of leucine. SDS-polyacrylamide gel electrophoresis of the protein fractions indicated similarities in the prolamin fraction and differences in the albumin-globulin and glutelin fractions of the different varieties.     

Analysis of protein fractions and some minerals present in chan (Hyptis suaveolens L.) seeds

Chan (Hyptis suaveolens L.) seeds have been used as food as well as in traditional medicine in several countries of America, Asia and Africa. Chan seed protein content was 13.9% on dry weight basis. Analysis of its protein composition showed 39% globulins, 36% glutelins, 24% albumins, and 1% prolamins. By defatting the flour with chloroform/methanol, it increased the extracted proteins and improved the protein band resolution after SDS-PAGE, showing 5 albumin bands, 8 globulin bands, and 2 prolamin and glutelin bands. The aromatic amino acid content in chan seeds is higher than those of other grains including maize, with good levels of branched chain amino acids. In general, except for lysine, it has a well-balanced amino acid composition, providing a good supply of almost all the essential amino acids for the different age groups. Magnesium content was high, whereas calcium, potassium, and phosphorous were in the average range when compared to barley, oat, rice, and wheat. The present results indicate that seeds from the chan plant could be relevant because of their nutritional properties and they have the potential to be widely used in the production of high-quality food. PRACTICAL APPLICATION: Chan seeds are presently used in a very limited manner as a food source; however, considering their high quality composition, they have the potential for a more extended use in the food industry.     

Importance of dietary protein level in the carcass analysis method for determining net protein utilisation in the chick

Two series of studies concerning chick NPU (net protein utilisation) determinations were carried out. In the first, two levels of dietary protein were compared with diets deficient in methionine or lysine. While the 10% protein level gave higher absolute NPU values than the 13% level, the former may lead to erroneous conclusions if the dietary protein is deficient in lysine. Since lysine is required in very low amounts for maintenance and the 10% protein level provides little more than the maintenance needs of the chick, the 13% level is to be preferred; this level provides sufficient excess for growth purposes so that a lysine deficiency can be more effectively recognised by the NPU value obtained. In the second series of experiments, three levels of fibre and maize oil were included factorially in a 13% protein diet composed of isolated soya protein supplemented with methionine. The combination of 3% fibre and 6% maize oil gave considerably higher NPU values than were obtained with any of the other combinations, although there was a general trend for higher NPU values with increased dietary energy. No adequate explanation for this finding is available at present.     

Effects of Dehydration and Soy Fortification on Physicochemical, Nutritional and Sensory Properties of Ghanaian Fermented Maize Meal

Fermented maize meal was air dried at 60°C and fortified with defatted soy flour at 0%, 10% and 20% replacement levels on dry basis. The effects on protein quality were determined by chick growth response studies and amino acid analysis, while sensory characteristics were evaluated by triangle and preference tests. Air drying did not affect chick growth response but slightly reduced preference of the meal. The drying caused only 6% and 16% losses in total and available lysine contents, respectively. Soy fortification of air-dried maize meal at 10% improved sensory preference to the same degree as freshly fermented meals and increased the protein quality significantly over both freeze-dried unfortified control and air-dried unfortified meals. Twenty percent soy fortified maize meal had low sensory score although the nutritive value was substantially increased.     

Nitrogen fertilization,yield and protein quality of a normal and a high-lysine maize variety

A normal and a high-lysine genotype (Opaque-2) of grain maize were grown in a field trial at nitrogen levels ranging from 35 to 276 kg N/ha. Nitrogen supply increased the yield and protein content of the grains in both varieties. At all doses of nitrogen, the contents of the limiting essential amino acids lysine and tryptophan were higher in the protein of the high-lysine mutant than in the protein of the control variety. When N supply was increased protein quality was lowered to a lesser extent in the Opaque-2 than in the conventional maize.     

Effects of heat treatment on lysine in soya protein

Total lysine and available lysine were used For predicting the damage to lysine in soya protein heated with glucose and in alkali. The amounts of both types of lysine decreased during the treatments. The content of total lysine was much higher than that of available lysine. In soya protein heated with glucose, the available lysine content decreased by 78-85 % and that of total lysine by 17-40 %. In soya protein heated in alkali, available lysine decreased by 7-24% and total lysine by 7-13%. Since available lysine was more sensitive, changes in total lysine underestimated the nutritional damage.     

Evaluation of maize gluten meal as a protein source in egg production with and without supplements of L-lysine and DL-methionine

Maize gluten meal has been examined as the sole source of supplementary protein in cereal-based high energy diets for caged hens and compared with a high energy diet containing white fish meal. Three levels of maize gluten meal were fed, 8.25, 12.25 and 15.25%, with and without supplements of L -lysine HCl or L -lysine HCl and DL-methionine to provide total crude protein of 12.9, 16.1 and 18.7% in the diets. Egg production on the unsupplemented maize gluten meal diets was lower than for the fish meal diet. The production data for the diets containing 8.25, 12.25 and 15.25% maize gluten meal showed a significant rise in production with each addition of protein. The addition of lysine to the maize gluten meal diets also caused a significant increase in production at each protein level. Methionine supplements did not improve the performance of the diets already supplemented with lysine. Improvements in food conversion efficiency were directly related to the effects of treatment on egg production. The white fish meal diet gave the best food conversion efficiency. The most economic of the maize gluten meal diets contained 12.25% maize gluten meal supplemented with lysine. Egg yolk colour was significantly improved by the addition of maize gluten meal to the diets but pigmented flesh was noted in the birds receiving these diets. For maximum egg colour a level of maize gluten meal well below 8% would seem adequate.     

Progress in protein quality of maize

The protein quality of some improved protein quality maize varieties grown in Mexico was measured chemically (including amino acid analyses) and biologically, in N-balance experiments with growing rats. The protein content ranged from 10.61 to 12.84%. Lysine 100 g^?1 protein varied between 2.63% for a normal variety to 4.18% for one of the improved varieties. The tryptophan content in the improved varieties was increased by 40-100%. There was a highly significant (P<0.001) positive correlation (r=0.98) between biological value and lysine 100 g^?1 protein whereas the relationship between protein and available carbohydrate was not significant. True protein digestibility was very high and above 95% in all samples. Biological value, however, was higher by 10-15 percentage units in the improved materials compared to the normal maize.     

Comparison of Lupinus angustifolius protein digestibility in dependence on protein,amino acids,trypsin inhibitors and polyphenolic compounds content

Lupine seeds are proposed as a source of valuable protein in human and animal nutrition. However, not only protein content but its bioavailability is important. Thus, the protein digestibility of twenty Lupinus angustifolius varieties seeds and the impact of some factors (protein and polyphenols content, trypsin inhibition and amino acids composition) on the protein digestion were discussed. Composition as well as the digestibility of these seeds was influenced by variety, weather conditions (precipitations) and place of cultivation (soil quality). The average digestibility of the seeds was 46%. The positive impact on the digestibility had the extractivity of the protein. Higher than it was expected activity of trypsin inhibitors (even up to ~32%) in some varieties influenced the protein availability, while the lysine and phenolic compounds content did not affect digestibility. The content of compounds influencing protein digestibility depends both on variety as well as on agronomical conditions.     

Effects of protein content on the distribution and properties of rice protein

The protein of brown rice became more evenly distributed as protein content increased. Kjeldahl protein content of brown rice provided a better indication of milled rice protein content than histological examination of individual grains because protein content varied among grains. The increase in protein content was mainly due to an increase in the number of protein bodies. Screening 10 493 varieties from the world rice collection for lysine content by dye-binding capacity showed that lysine content of rice protein varied only by at most 0.5 % point at any protein level. A negative correlation between the lysine content of protein and protein content of brown and milled rice was observed only in samples with protein below 10%. As protein content increased water-soluble nitrogen also increased as a percentage of brown rice.     

Effect of cooking on protein quality of chickpea (Cicer arietinum) seeds

Amino acid composition and in vitro protein digestibility of cooked chickpea were determined and compared to raw chickpea seeds. Heat treatment produced a decrease of methionine, cysteine, lysine, arginine, tyrosine and leucine, the highest reductions being in cysteine (15%) and lysine (13.2%). Protein content declined by 3.4% and in vitro protein digestibility improved significantly from 71.8 to 83.5% after cooking. The decrease of lysine was higher in the cooked chickpea seeds than in the heated protein fractions, globulins and albumins. The structural modification in globulins during heat treatment seems to be the reason for the increase in protein digestibility, although the activity of proteolytic inhibitors in the albumin fraction was not reduced. Results suggest that appropriate heat treatment may improve the bioavailability of chickpea proteins.     

Protein quality and amino acid-protein relationships of maize,sorghum and rice grain as influenced by nitrogen,phosphorus, potassium and soil moisture stress

In pot and field experiments cereals were grown with greatly differing rates of N, P and K applications. For maize and sorghum, soil moisture levels were also varied. N applications, P- and K-deficiency, and moisture stress generally increased the total N content of grain, from 1.06 to 2.68, 1.01 to 2.42 and 0.81 to 2.33% (as % of DM) for maize, sorghum and rice, respectively. P, K and moisture stress affected the amino acid composition only indirectly through their effects on N concentration. In all three cereals increasing N concentrations were associated with decreases in crude protein of lysine, methionine, cystine, threonine, tryptophan and, generally, with increases of isoleucine, leucine, phenylalanine and glutamate. Lysine as a percentage of dry matter increased up to the highest N concentration in all three cereals. Linear regressions with significant correlation coefficients were found between concentrations of most (g 16 g^?1 N) or all (mg 100 g^?1 DM) amino acids and N content of grain. Based on all experimental data equations for lysine were: g 16 g^?1 N=4.44–0.89 × %N; 4.23–0.86 × % N; 4.39–0.42 × % N for maize, sorghum and rice, respectively. Correction of P- and K-deficiency decreased N content of grain and resulted in higher lysine content and better nutritional value of grain protein, whereas correction of N-deficiency had the opposite effect. The amino acid composition of rice was much more balanced than that of maize and sorghum with a leucine/isoleucine ratio of 2 compared to that of 3 in maize and sorghum. In rat feeding experiments true digestibility of maize and sorghum protein was high (about 95%) but increased only slightly with increasing N in grain, whereas the biological value decreased considerably, from 63 to 55 and from 70 to 58, respectively. The chemical score underestimated the nutritional value of both cereal proteins.     

Effect of soaking process on nutritional quality and protein solubility of some legume seeds

Legume seeds (soy bean, lupin and bean seeds) were soaked in 0.5% sodium bicarbonate in attempt to evaluate their nutritional quality and protein solubility index. Soaking process led to an increase in the hydration coefficient, seed weight, total protein, ash, fat, fiber, while non protein nitrogen, total carbohydrates, starch, stachyose, raffinose, reducing sugars, and minerals (except Na) were decreased. All antinutritional factors such as phytic acid, tannin, trypsin inhibitor and hemagglutinin activity were decreased during soaking in 0.5% sodium bicarbonate; it was the same for the protein solubility in different solutions, while the in-vitro protein digestibility and available lysine were increased.     

The protein and the amino acid composition of some rice and maize varieties grown in North Vietnam

The protein and amino acid composition of several rice and maize varieties grown in North Vietnam, and their digestibility, was determined. The protein content (N×5.95) of rice cultivars ranged from 7.0 to 10.8% of which 70–80% was in the glutelin fraction. The true digestibility was relatively good (87.6–91.8%). In general, lysine and threonine were found to be the first and second nutritionally limiting amino acids, except for two varieties, which had a low content of sulphur-containing amino acids. The protein content of maize cultivars ranged from 8.4 to 12.9%. Zein and glutelin were the main components occurring in near-equal quantities (except in the opaque-2 mutant). The overall amino acid distribution was similar to that of maize grown in other countries. Lysine levels were relatively low, and it was the first nutritionally limiting amino acid, except in the opaque-2 cultivar, tryptophan being the second one. The digestibility ranged from 87.5 to 91.1%.     

Opportunities for nutritionally enhanced maize and wheat varieties to combat protein and micronutrient malnutrition

Naturally occurring variation detected in the germplasm of maize and wheat, two of the top three cereal crops in the world, provides options for incorporating higher levels of iron, zinc, and beta-carotene into these grains. In addition, quality protein maize (QPM) has been developed from naturally occurring variation; its seed contains enhanced levels of lysine and tryptophan, two essential amino acids lacking in cereals. The International Maize and Wheat Improvement Center, along with its many partners, has identified several maize and wheat varieties with 25% to 30% higher grain iron and zinc concentrations. Wild relatives of wheat have been found to contain some of the highest iron and zinc concentrations in the grains. Although these accessions are often low yielding and have poor grain quality, backcrossing to bread wheat could result in highly nutritious cultivars. Options are now available for conventional and biotechnology-assisted improvement of the nutritional content of maize and wheat germplasm.