Low Lysine Content Research Articles

New Insights into the Genetic Basis of Lysine Accumulation in Rice Revealed by Multi-Model GWAS.

Lysine is an essential amino acid that cannot be synthesized in humans. Rice is a global staple food for humans but has a rather low lysine content. Identification of the quantitative trait nucleotides (QTNs) and genes underlying lysine content is crucial to increase lysine accumulation. In this study, five grain and three leaf lysine content datasets and 4,630,367 single nucleotide polymorphisms (SNPs) of 387 rice accessions were used to perform a genome-wide association study (GWAS) by ten statistical models. A total of 248 and 71 common QTNs associated with grain/leaf lysine content were identified. The accuracy of genomic selection/prediction RR-BLUP models was up to 0.85, and the significant correlation between the number of favorable alleles per accession and lysine content was up to 0.71, which validated the reliability and additive effects of these QTNs. Several key genes were uncovered for fine-tuning lysine accumulation. Additionally, 20 and 30 QTN-by-environment interactions (QEIs) were detected in grains/leaves. The QEI-sf0111954416 candidate gene LOC_Os01g21380 putatively accounted for gene-by-environment interaction was identified in grains. These findings suggested the application of multi-model GWAS facilitates a better understanding of lysine accumulation in rice. The identified QTNs and genes hold the potential for lysine-rich rice with a normal phenotype.

Genomic prediction reveals unexplored variation in grain protein and lysine content across a vast winter wheat genebank collection.

Globally, wheat (Triticum aestivum L.) is a major source of proteins in human nutrition despite its unbalanced amino acid composition. The low lysine content in the protein fraction of wheat can lead to protein-energy-malnutrition prominently in developing countries. A promising strategy to overcome this problem is to breed varieties which combine high protein content with high lysine content. Nevertheless, this requires the incorporation of yet undefined donor genotypes into pre-breeding programs. Genebank collections are suspected to harbor the needed genetic diversity. In the 1970s, a large-scale screening of protein traits was conducted for the wheat genebank collection in Gatersleben; however, this data has been poorly mined so far. In the present study, a large historical dataset on protein content and lysine content of 4,971 accessions was curated, strictly corrected for outliers as well as for unreplicated data and consolidated as the corresponding adjusted entry means. Four genomic prediction approaches were compared based on the ability to accurately predict the traits of interest. High-quality phenotypic data of 558 accessions was leveraged by engaging the best performing prediction model, namely EG-BLUP. Finally, this publication incorporates predicted phenotypes of 7,651 accessions of the winter wheat collection. Five accessions were proposed as donor genotypes due to the combination of outstanding high protein content as well as lysine content. Further investigation of the passport data suggested an association of the adjusted lysine content with the elevation of the collecting site. This publicly available information can facilitate future pre-breeding activities.

Biological completeness of protein and its role in farm animals feeding

Purpose. To study the biological completeness of the feed protein, including green mass of cereal and leguminous fodder crops. To find out the role of their aminoacid composition for farm animals feeding. Methods. Sampling was carried out in accordance with State Standard of Ukraine ISO 6497:2005, determination of the content of moisture and other volatile substances – State Standard of Ukraine ISO 6496:2005, nitrogen and crude protein – State Standard of Ukraine 7169:2010. The amino acid composition of protein was determined on the AAA500 ion-exchange automatic analyzer. Results. Cereal grain proteins are characterized by a relatively low content of lysine, threonine, and corn grain – of tryptophan. The richest source of essential aminoacids among plant feeds is soybean meal, which contains, on average, 43% of protein. The complex use of sunflower and rapeseed meal maximally balances the protein nutrition of animals and the. But this raw material should be checked for protein and non-protein nitrogen content to confirm its natural origin. For ruminants, the green mass of cereal crops is a valuable feed, because the crude protein content in it reaches 12% in the tillering phase, but decreases two times in the earing phase. In the green mass of legumes, alfalfa and chickweed, the content of crude protein in the branching phase is at the level of 27-29% in terms of absolutely dry matter, and in the flowering phase –15-17%. In terms of the content of individual aminoacids, the green mass of leguminous crops exceeds the green mass of cereal fodder crops by 1.5-2 times. Conclusions. The content of lysine in triticale and rye grains is the highest – 3.6%, while in wheat – only 2.8%. An important condition in solving the problem of animal protein nutrition is its multicomponent nature, which ensures a better balance in terms of aminoacids. In terms of the content of individual aminoacids, the green mass of leguminous crops exceeds the green mass of cereal fodder crops by 1.5-2 times, while the green mass of cereal crops is characterized by a lower protein content compared to legumes.

Influence of Dietary Lysine Level on Growth Performance, Feed Efficiency, and Body Composition of Sangkuriang Catfish (Clarias gariepinus var. Sangkuriang) Fingerlings

The high consumer demand in Indonesia encourages catfish farmers to conduct an intensive culture. A low feed efficiency mainly occurs in cultivating Sangkuriang catfish resulting in poor growth. This condition might be caused by low lysine content, as lysine is an essential amino acid that the fish cannot synthesize. The present study aimed to investigate the effect of lysine supplementation in feed on protein digestibility, feed efficiency, and growth of Sangkuriang catfish (Clarias gariepinus var. Sangkuriang) fingerlings. The study used 270 Sangkuriang catfish with an average wet weight of 7.54 ± 0.13 g/fish. The experimental feed contained protein, energy, and amino acid, and then various doses of lysine were added to the experimental feed: (1) 0.0%, (2) 0.5%, (3) 1.0%, (4) 1.5%, (5) 2.0%, and (6) 2.5%. Weight gain (WG), protein digestibility (ADCp), the efficiency of feed utilization (EFU), relative growth rate (RGR), feed conversion ratio (FCR), protein efficiency ratio (PER), and protein retention (PR) of catfish were evaluated for 8 weeks. The results found that the supplementation of lysine in feed significantly (P < 0.05) influenced WG, ADCp, EFU, RGR, FCR, PER, and PR of Sangkuriang catfish fingerling. However, there was no significant effect (P > 0.05) on the SR of Sangkuriang catfish fingerling. The supplementation of 1% lysine/kg feed was the optimal dose to improve the feed efficiency and growth of Sangkuriang catfish fingerlings by 83.79% and 3.94%/day, respectively. Therefore, the supplementation of lysine could increase Sangkuriang catfish production.

PSXV-19 Effects of L-Glutamine and L-Glutamate on Nursery Pigs fed Diets with low Digestible Lysine Content

Abstract This study investigated the effects of L-glutamine and L-glutamate (Gln/Glu) on growth performance and intestinal health of nursery pigs fed low digestible lysine diets. Piglets (n = 150; 21-day-old; 5.6 ± 0.55 kg initial BW) were distributed in a randomized block design, with three treatments and ten replicates. Experimental diets were fed from 21 to 33 and 33 to 47 d of age. The treatments consisted of control, standard lysine level; low-lys, 90% of the lysine level of the control diets; low-lys + Gln/Glu, low-lys diets supplemented with 1.2% and 0.8% of Gln/Glu (AminoGut, Ajinomoto) per phase. Alanine, inert and starch were used to make treatments isoproteic and isocaloric. Data were analyzed with SAS 9.4 PROC GLM. From 21 to 33 d, pigs fed control or low-lys + Gln/Glu diets had improved ADG, G:F, and 33-d BW compared with those fed low-lys diets (P < 0.05). From 21 to 47 d, pigs fed control or low-lys + Gln/Glu diets had improved ADG and 47-d BW compared with those fed low-lys diets (P < 0.05). The supplementation of Gln/Glu in the diets improved G:F compared with those fed low-lys (P < 0.05). Pigs fed low-lys + Gln/Glu had greater duodenum villus height compared with those fed low-lys (P < 0.05), and pigs fed the control diet had intermediate results. Pigs fed control diets had increased presence of goblet cells in duodenum compared with those fed low-lys (P < 0.05), and pigs fed the low-lys + Gln/Glu diet had intermediate results. Pigs fed low-lys + Gln/Glu diets had increased presence of goblet cells in jejunum compared with the other treatments (P < 0.05). The diets did not influence Peyer's patches count (P > 0.05). In conclusion, supplementation of Gln/Glu on low lysine diets improved nursery pigs growth performance and intestinal heath.

Biorefined organic grass-clover protein concentrate for growing pigs: Effect on growth performance and meat fatty acid profile

The purpose of the study was to extract protein from organic grass-clover in a green biorefining process and perform a dose-response feeding experiment with pigs on feed utilization, performance and slaughter quality. Forty-eight pigs were fed one of four experimental diets from 1 week post-weaning to slaughter. The diets consisted of a control diet and diets with 5, 10, or 15 % freeze-dried extracted grass-clover protein included. The extracted protein had a crude protein content of 458 g/kg dry matter, a content of total sulphur-containing amino acids comparable to soybean press cake but a lower lysine content. Acid-insoluble residue constituted 215 g/kg dry matter, and the dominating fatty acid was α-linoleic acid. Addition of grass-clover protein extract to the diet did not affect feed intake or growth in starter, grower, or finisher pigs, and no difference was found in animal slaughter weight. The meat percentage measured at slaughter increased linearly with inclusion of grass-clover protein in the feed. Increased addition of grass-clover increased the content of n-3 fatty acids and lowered the n-6/n-3 ratio in adipose tissue, liver, and Longissimus dorsi muscle as well as the α-tocopherol content. In conclusion, this study shows that protein extracted from organic forages through green biorefining can be used as a protein source for organic slaughter pigs.

A Novel Carboxylesterase Derived from a Compost Metagenome Exhibiting High Stability and Activity towards High Salinity.

Halotolerant lipolytic enzymes have gained growing interest, due to potential applications under harsh conditions, such as hypersalinity and presence of organic solvents. In this study, a lipolytic gene, est56, encoding 287 amino acids was identified by functional screening of a compost metagenome. Subsequently, the gene was heterologously expressed, and the recombinant protein (Est56) was purified and characterized. Est56 is a mesophilic (Topt 50 °C) and moderate alkaliphilic (pHopt 8) enzyme, showing high thermostability at 30 and 40 °C. Strikingly, Est56 is halotolerant as it exhibited high activity and stability in the presence of up to 4 M NaCl or KCl. Est56 also displayed enhanced stability against high temperatures (50 and 60 °C) and urea (2, 4, and 6 M) in the presence of NaCl. In addition, the recently reported halotolerant lipolytic enzymes were summarized. Phylogenetic analysis grouped these enzymes into 13 lipolytic protein families. The majority (45%) including Est56 belonged to family IV. To explore the haloadaptation of halotolerant enzymes, the amino acid composition between halotolerant and halophilic enzymes was statistically compared. The most distinctive feature of halophilic from non-halophilic enzymes are the higher content of acidic residues (Asp and Glu), and a lower content of lysine, aliphatic hydrophobic (Leu, Met and Ile) and polar (Asn) residues. The amino acid composition and 3-D structure analysis suggested that the high content of acidic residues (Asp and Glu, 12.2%) and low content of lysine residues (0.7%), as well as the excess of surface-exposed acidic residues might be responsible for the haloadaptation of Est56.

Insights from the salt bridge analysis of malate dehydrogenase from H. salinarum and E.coli.

Halophilic proteins have greater abundance of acidic over basic residues in sequence. In structure, the surface is decorated by negative charges, with lower content of Lysine. Using sequence BLOCKs and 3D model of malate dehydrogenase from halophilic archaea (Halobacterium salinarum; hsMDH) and X-ray structure from mesophilic bacteria (E. coli; ecMDH), we show that not only acidic and basic residues have higher mean relative abundance (MRA) and thus, impart higher polarity to the sequences, but also show their presence in the surface of the structure of hsMDH relative to its mesophilic counterpart. These observations may indicate that both the acidic and the basic residues have a concerted role in the stability of hsMDH. Analysis on salt bridges from hsMDH and ecMDH show that in the former, salt bridges are highly intricate, newly engineered and global in nature. Although, these salt bridges are abundant in hsMDH, in the active site the design remains unperturbed. In high salt where hydrophobic force is weak, these salt bridges seem to play a major role in the haloadaptation of the tertiary structure of hsMDH. This is the first report of such an observation.

Nutritional quality of maize–groundnut composite flours and resultant porridges

PurposeThe purpose of this study was to composite maize, a cereal grain with low protein and lysine content, with groundnut a rich source of protein, to improve the nutritional quality of maize–groundnut composite flours and their resultant porridges.Design/methodology/approachDefatted and full fat groundnut flours were used to prepare maize–groundnut composite flours and porridges at the ratio of 100:0, 55:45, 70:30 and 85:15, respectively. They were analyzed for proximate composition, energy value, amino acid and fatty acid profiles.FindingsCompositing maize with groundnut significantly (p ≤ 0.05) increased proteins from 10 per cent in maize flour to up to 21 per cent in composite porridge (denoted DFC1). The energy values for composite porridges were 434 Kcal/100 g when compared with 398 Kcal/100 g established for maize porridge alone. Lysine content was three times higher in composite flours than for maize flour, while for composite porridges, lysine was four times higher than in maize porridge. There was an increase of 35 per cent in oleic acid content when maize flour was composited with groundnut flour.Research limitations/implicationsFurther research is required to evaluate the properties of full fat and defatted maize–groundnut porridges and their effects on consumer acceptability.Originality/valueIt can be concluded that compositing maize with full fat and defatted groundnut has the capability of improving the nutritional quality of cereal-based diets consequently contributing to a significant increase in nutritional security of African populations and those of other developing countries of the world.

Silanized maghemite for cross-linked enzyme aggregates of recombinant xylanase from Trichoderma reesei

Numerous state-of-the-art technologies and new types of carriers have been developed recently to improve enzyme immobilization. Cross-linked enzyme aggregate (CLEA) technology is a lucrative prospect, as several robust biocatalysts have been generated using this simple method of carrier-free immobilization with the possibility of using semipurified enzyme. However, the low lysine content in the enzyme remains a challenge for effective crosslinking. In this work, maghemite (γ- Fe2O3), a recently sought after nanoparticle, was silanized with (3-aminopropyl) triethoxysilane (APTES) for use in the preparation of cross-linked enzyme aggregates of recombinant xylanase from Trichoderma reesei (Xyl-CLEA-silanized maghemite). Prior screening revealed ethanol to be the best precipitant, and a 0.2: 1 (v:v) glutaraldehyde to enzyme ratio was essential to form active CLEAs. The Xyl-CLEA-silanized maghemite succeeded in increasing the activity recovery 1.66- and 1.5-fold compared to conventional Xyl-CLEAs and Xyl-CLEA-BSA, respectively. The silanization of maghemite with APTES was proven feasible when a 0.0075:1 (v:v) maghemite to enzyme ratio was able to achieve a 78% activity recovery of the xylanase aggregates, whereas the non-silanized maghemite only achieved a 47% activity recovery. At an elevated temperature of 60°C, Xyl-CLEA-silanized maghemite retained approximately 50% of its initial activity, compared to the free enzyme, for which the activity recovery had plummeted to 20%. Conversely, Xyl-CLEA suffered a total loss of activity at this temperature, whereas Xyl-CLEA-BSA retained only a 6% activity. Xyl-CLEA-silanized maghemite also successfully retained more than 50% of its activity after up to 6 cycles, whereas Xyl-CLEA retained approximately 10% of its initial activity after only 5 cycles. The surface morphology, particle size and loading of silanized maghemite were confirmed by field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectroscopy. The combination of the effective surface modification, high enzyme activity recovery, improved stability and enhanced reusability of Xyl-CLEA-silanized maghemite presents an attractive process for xylanase immobilization and provides a promising catalyst for the biomass industry.

A new allele of γ‐kafirin gene coding for a protein with high lysine content in Mexican white sorghum germplasm

Low protein digestibility and lysine content of white sorghum grain limit its use as a foodstuff. The increase in γ-kafirin cross-linking, has an important role in the reduction of protein digestibility. The objective of this study was to characterize the γ-kafirin gene in 12 Mexican tannin-free white sorghum genotypes and its relationship with protein digestibility and lysine content. Two alleles of γ-kafirin gene were identified: alleles 1 and 7. The predicted amino acid sequence of allele 7 showed seven point mutations; six were silent, and one missense (C235G), causing the substitution P79A in the deduced amino acid sequence. In silico analysis showed that γ-kafirin codified by allele 1 has five α-helixes without disulfide bonds, while γ-kafirin coding by allele 7 has four α-helixes and three disulfide bonds. Genotypes with allele 7 had higher lysine content than those with allele 1, showing no differences in the kafirin electrophoretic profile, neither a correlation with the protein content nor the in vitro pepsin digestibility. Mexican tannin-free white sorghum genotypes showed two γ-kafirin alleles, 1 and 7. Allele 7 was associated with higher lysine content; in silico analysis showed that the substitution of P79A in this allele could modify γ-kafirin secondary structure. © 2015 Society of Chemical Industry.

The nutritional context of the Pueblo III depopulation of the northern San Juan: Too much maize?

The abandonment of the Four Corners area in the U.S. Southwest is a long-standing problem in American archeology. Recent work has shown that the terminal occupation was concentrated into a limited number of large defensive sites. This resulted in an extreme emphasis on maize, which was nutritionally unsustainable because of its low lysine and tryptophan content. I describe the processes that led to this settlement pattern and the limitations of the Pueblo II–III maize-based diet. I then explain how the combination of the settlement pattern and the extreme reliance on maize resulted in a nutritionally fragile situation that collapsed.

Functional properties of ovalbumin glycosylated with carboxymethyl cellulose of different substitution degree

The glycation of hen ovalbumin (OVA) with carboxymethyl cellulose (CMC) was studied in an attempt to improve its functionality. OVA was dry-heated with CMC with three different degrees of substitution (0.69, 0.81, 0.89) at 60 °C and 79% relative humidity for 7 days. The emulsifying properties of OVA–CMC conjugates were strengthened remarkably with increasing substitution degree of CMC. The foam stability of OVA–CMC conjugates was improved strongly with the extension of incubation time while the foaming ability decreased. The rheological behaviors of all the three grafted products were similar. With the incubation time extension, it took more time for the formation of the protein gel network, and the thermal denaturation temperature of protein became higher. The glycation also produced OVA–CMC conjugates with higher surface hydrophobicity and lower content of lysine and arginine.

Dietary arginine requirement of juvenile blunt snout bream, Megalobrama amblycephala

A 9-week feeding trial was conducted to quantify the dietary arginine requirement of juvenile blunt snout bream. Six isonitrogenous and isoenergetic semi-purified diets (34.0% crude protein) were formulated to contain graded arginine levels (0.83% to 3.36% of dry weight) at 0.5% increments replaced by equal proportions of glycine. At the end of the feeding trial, the results showed that survival rate was not significantly affected by dietary arginine level. Final weight, specific growth rate (SGR), feed efficiency ratio (FER), protein efficiency ratio (PER) and protein productive value (PPV) increased with increasing dietary arginine level from 0.83 to 1.81% (P<0.05), thereafter showed a declining trend but the differences were not significant. Whole body compositions were independent of dietary arginine levels (P>0.05). Plasma arginine concentration increased with the increase of dietary arginine from 0.83% to 1.81%, and thereafter was relatively constant, while lower lysine content in plasma was observed in fish fed the diet with 3.36% arginine level compared to those fed diets with 0.83–2.35% arginine (P<0.05). Significantly higher plasma urea content was observed in fish fed diet with 3.36% arginine compared with those fed 0.83% arginine diet (0.83%). Significantly lower plasma total nitric oxide synthase (T-NOS) activities were observed in fish fed 0.83% arginine diet than those fed diets with 2.35–3.36% arginine. Plasma superoxide dismutase (SOD) activities and ammonia contents were not significantly affected by dietary arginine levels. Based on SGR, FER and PER, the optimal dietary arginine requirement of juvenile blunt snout bream was estimated to be 2.46% of the diet (7.23% of dietary protein), 2.28% (6.71% of dietary protein) and 2.26% of the diet (6.65% of dietary protein), respectively.

Nutritional and functional characteristics of Erophaca baetica seeds, a legume endemic to the Mediterranean region

Erophaca baetica is a legume endemic to the Mediterranean region. Although the fruits and seeds are large, the presence of the “locoism” which produces the alkaloid, swainsonine has prevented its use as animal feed or for human nutrition. Their protein content and chromatographic profile, amino acid composition, fatty acid composition, and polyphenol contents have been determined in order to explore the potential of the E. baetica seeds as a source of dietary protein with functional components. The protein content was found to be 36% (w/w), and an amino acid analysis revealed a deficiency in sulphur amino acids, tryptophane, and lysine. The low lysine content is probably due to the abundance of alkaloids metabolically derived from this amino acid. Oleic and linoleic acids are the major fatty acids in the seeds. The antioxidant activity of polyphenol extracts was higher than the activity of the polyphenols extracted from most edible legume seeds. Hence, E. baetica seeds represent a promising source of functional and nutritional components on the condition that the anti-nutritional alkaloids are previously removed.

Effect of Drying Conditions and Level of Condensed Distillers Solubles on Protein Quality of Wheat Distillers Dried Grain with Solubles

Reduced protein quality is one of the concerns currently confronting the supply and utilization of wheat distillers dried grain with solubles (DDGS) as an animal feed ingredient. This study assessed the protein quality of wheat DDGS, expressed as acid detergent insoluble crude protein (ADICP) and lysine content, by blending wet distillers grain (WDG) with varying condensed distillers solubles (CDS) levels and drying using forced air convection, microwave, and microwave–convection methods. As the CDS level was increased, the protein content of wheat DDGS generated from the three drying methods increased. Interactions of CDS level with drying air temperature, microwave power, and microwave–convection settings had a significant effect (p < 0.05) on average ADICP and lysine contents. Higher ADICP and lower lysine contents were observed in samples dried at higher temperature, microwave power, and microwave convection settings. Further, the CDS level significantly affected the color parameters of microwave- and microwave–convection-dried samples and the drying air temperature–CDS level interaction significantly affected the color of forced air convection–dried samples. Significant lysine content–redness, ADICP–lightness color parameter, and ADICP–total color difference correlations were found in forced air convection–, microwave-, and microwave–convection-dried samples, respectively. Microwave and microwave–convection drying achieved desirable protein quality associated with low-temperature drying at much shorter times.

Increasing Lysine Content of Waxy Maize through Introgression of Opaque-2 and Opaque-16 Genes Using Molecular Assisted and Biochemical Development

The low lysine content of waxy maize cannot meet the nutritional requirements of humans, livestock, or poultry. In the present study, the high-lysine genes o2 and o16 were backcrossed into wx lines using the maize high-lysine inbreds TAIXI19 (o2o2) and QCL3021 (o16o16) as donors and the waxy maize inbred line QCL5019 (wxwx) as a receptor. In the triple-cross F1, backcross, and inbred generations, the SSR markers phi027 and phi112 within the wx and o2 genes and the SSR marker umc1121 linked to the o16 gene were used for foreground selection. Background selection of the whole-genome SSR markers was performed for the selected individuals. The grain lysine content was determined using the dye-binding lysine method. The waxiness of the grain was determined with the I2-KI staining and dual-wavelength spectrophotometric analysis. The BC2F2 generation included 7 plants of genotype wxwxo2o2O16_, 19 plants of genotype wxwxo16o16O2_, and 3 plants of genotype wxwxo2o2o16o16. In these seeds, the average amylopectin content was 96.67%, 96.87%, and 96.62%, respectively, which is similar to that of QCL5019. The average lysine content was 0.555%, 0.380%, and 0.616%, respectively, representing increases of 75.1%, 19.9%, 94.3%, respectively, over QCL5019. The average genetic background recovery rate of the BC2F3 families was 95.3%, 94.3%, 94.2%, respectively. Among these 3 wxwxo2o2O16O16 families, 4 wxwxo2o2O16o16 families, and 3 wxwxo2o2o16o16 families, the longest imported parent donor fragment was 113.35 cM and the shortest fragment was 11.75 cM. No significant differences in lysine content were found between the BC2F4 seeds and the BC2F3 seeds in these 10 families. This allowed us to increase the lysine content of waxy corn and produce seeds with excellent nutritional characteristics suitable for human consumption, animal feed, and food processing. This may be of significance in the breeding of high-quality corn and in improvement of the nutrition of humans, livestock, and poultry.

Standardised amino acid digestibility of wheat distillers’ dried grains with solubles in force-fed cockerels

1. In recent years, policies encouraging the production of ethanol from maize or wheat have stimulated an increased production of distillers’ dried grains with solubles (DDGS) for which the nutritional value for poultry is poorly described, especially in the case of wheat DDGS. 2. DDGS samples (19) were obtained from 7 plants in Europe from June to September 2007. Each sample was analysed for chemical composition and 10 representative samples were measured for amino acid (AA) content and their standardised digestibility (SDD) in caecectomised cockerels. Lightness score (L) of each DDGS was also measured. 3. Results indicated a rather stable crude protein content (327 to 392 g/kg DM) but the AA profile was variable between samples. Lysine (LYS) was the most affected AA with contents ranging between 0·83 and 3·01 g/100 g CP. In addition, only 0·76 of total LYS were free if estimated by the fluoro-dinitro-benzene procedure and 0·85 of total LYS were free if estimated by the furosine procedure. 4. The SDD of LYS was also highly variable (−0·04 to 0·71) with the lowest values observed for DDGS samples with a low LYS content in CP; these latter samples had also a high occurrence of Maillard reactions and low L values (<50). Consequently, both LYS content in CP (r = 0·63) and SDD of LYS (r = 0·64) values were positively related with L. 5. Our data indicate that LYS SDD can be accurately predicted from LYS content in CP according to a quadratic (R 2 = 0·94) or a linear-plateau model (R 2 = 0·90; breakpoint for 1·9 g/100 g lysine in CP and a 0.63 plateau SDD value).

Composition and amino acids ileal digestibility of wheat distillers dried grains and solubles in pigs: Sources of variability

In recent years, policies encouraging the production of ethanol from corn or wheat have stimulated an increased production of distillers dried grains with solubles (DDGS) whose nutritional value for pigs is little described. Seventeen wheat DDGS samples were obtained from 7 different plants in Europe from July to September 2007. Each sample was analyzed and 10 representative samples were measured for amino acids (AA) content and their standardized ileal digestibility (SID) in pigs. Lightness score (L) of each DDGS was also measured. Our results indicate a rather stable crude protein content (32.6 to 38.9% DM basis; average: 36.1% DM basis) whereas lysine was the most affected AA with contents ranging between 0.82 and 3.00% of crude protein (CP; N*6.25). In addition, lysine SID was also variable (9 to 82%) with the lowest values observed in DDGS with low lysine level in CP. In fact, samples with low lysine content in CP and low SID of lysine had low lightness values (L < 50) and a subsequent high occurrence of Maillard reactions. Consequently, both lysine content (R = 0.63) and lysine SID ( R = 0.68) values were positively correlated with lightness and DDGS samples that were lighter in colour had higher total and digestible AA levels. Our data indicate that lysine SID can be accurately predicted from lysine content in CP with a quadratic model (R² = 0.87) or a linear-plateau model (R² = 0.80 with a breakpoint for lysine content in CP of 1.9% and SID at plateau of 68%). This also suggests that wheat DDGS with lysine content in CP lower than 1.9% should be avoided in pig diets.

Ricin A Chain Insertion into Endoplasmic Reticulum Membranes Is Triggered by a Temperature Increase to 37 °C

After endocytic uptake by mammalian cells, the heterodimeric plant toxin ricin is transported to the endoplasmic reticulum (ER), where the ricin A chain (RTA) must cross the ER membrane to reach its ribosomal substrates. Here, using gel filtration chromatography, sedimentation, fluorescence, fluorescence resonance energy transfer, and circular dichroism, we show that both fluorescently labeled and unlabeled RTA bind both to ER microsomal membranes and to negatively charged liposomes. The binding of RTA to the membrane at 0-30 °C exposes certain RTA residues to the nonpolar lipid core of the bilayer with little change in the secondary structure of the protein. However, major structural rearrangements in RTA occur when the temperature is increased. At 37 °C, membrane-bound toxin loses some of its helical content, and its C terminus moves closer to the membrane surface where it inserts into the bilayer. RTA is then stably bound to the membrane because it is nonextractable with carbonate. The sharp temperature dependence of the structural changes does not coincide with a lipid phase change because little change in fluorescence-detected membrane mobility occurred between 30 and 37 °C. Instead, the structural rearrangements may precede or initiate toxin retrotranslocation through the ER membrane to the cytosol. The sharp temperature dependence of these changes in RTA further suggests that they occur optimally in mammalian targets of the plant toxin.