Safety assessment by in vitro digestibility and allergenicity of genetically modified maize with an amaranth 11S globulin

Physicochemical, structural, and functional characterization of guar meal protein isolate (Cyamopsis tetragonoloba)

Guar korma and churi protein isolates were assessed for their physicochemical, nutritional, functional, structural, and digestibility properties for their application in the food industry. The water extracted protein isolate of guar korma showed a protein content of 89.7 % and a yield of 48.7 %. Water extracted protein isolate of guar korma showed an excellent protein efficiency ratio, essential amino acid/total amino acids (34.35 %), amino acid score, and protein digestibility corrected amino acid score values, suggesting the existence of high-quality proteins. Water extracted protein isolate of guar korma contains all the essential amino acids except Methionine and Cysteine, according to World Health Organization recommendations for children and adults. The protein profiling of water extracted protein isolate of guar korma was analyzed using 12 % sodium dodecyl sulfate polyacrylamide gel electrophoresis and indicated the presence of eight major protein bands in the range of 17-100 kDa. In vitro digestibility of water extracted protein isolate of guar korma showed the complete digestion of the abundant protein bands within 15 min. Further, the foaming capacity, water/oil holding capacity, and emulsifying stability of water extracted protein isolate of guar korma were comparable with soy protein isolate. Fourier Transform Infrared and Circular Dichroism spectral analysis revealed the presence of several aromatic groups and β-sheets, random coils respectively in water extracted protein isolate of guar korma. The morphological nature of the guar protein isolate was characterized by Scanning Electron Microscopy. Overall, these findings support that water extracted protein isolate of guar korma has excellent functional and nutritional properties and could be a potential alternative plant protein in food industries.

Characterization of in silico modeled synthetic protein enriched with branched-chain amino acids expressed in Pichia pastoris

We have designed earlier the 3-dimensional structure of protein enriched with 56% branched-chain amino acids (BCAA) based on an α-helical coiled-coil structure. The chemically synthesized DNA (BCAA51 gene) was expressed in Pichia pastoris and confirmed by SDS-PAGE and western blot analysis. In the present study, the purified recombinant protein was characterized using circular dichroism and data revealed that the secondary structure contained 53.5% α-helix, 3.2% β-strand, and 43.3% turns, which is in concurrence with the overall structure predicted by in silico modeling. The LC-ESI-MS/MS spectra revealed that three peptide masses showed similarity to peptides like EQLTK, LEIVIR, and ILDK, of the modeled BCAA51 protein with the sequence coverage of ~16% from N-terminal region. The N-terminal sequence of the first seven amino acid residues (EQLTKLE) was exactly matching with the in silico designed protein. In vitro digestibility of the protein using SGF and SIF showed the disappearance of ~11 kDa band and appearance of low molecular weight peptides, which indicated that the protein was easily digestible and non-allergenic, which is the overall objective of this study. Further in vivo digestibility and toxicology studies are required to conclusively utilize this protein as a supplement for the treatment of chronic liver diseases.

Biochemical, nutritional and functional properties of protein isolate and fractions from pumpkin (Cucurbita moschata var. Kashi Harit) seeds

Pumpkin seeds are rich source of nutritionally well-balanced proteins. The biochemical, nutritional, and functional properties of the protein isolate (PPI) and protein fractions from pumpkin seed were evaluated. Extraction method for PPI was optimized by varying NaCl (0, 0.5, 1 M) and flour-to-solution ratio (1:5, 1:10, 1:25), at pH 9.0. Proteins were extracted by Osborne procedure and the alkali fraction (AF, 45.82%) was found to be the predominant fraction. SDS-PAGE profile of PPI revealed major bands ranging from 50 to 7 kDa. AF contained all the essential amino acids (EAA) except lysine and threonine, as required by pre-school children (FAO/WHO). PPI and AF showed better protein efficiency ratio and EAA/TAA (total) %, indicating the presence of good quality proteins. Functional properties were found to be comparable with soybean protein isolate. Circular dichroism studies showed that water fraction comprised of α-helix and random coils, while salt and alkali fractions contained β-strand and coils.

Edible Safety Assessment of Genetically Modified Rice T1C-1 for Sprague Dawley Rats through Horizontal Gene Transfer, Allergenicity and Intestinal Microbiota

In this study, assessment of the safety of transgenic rice T1C-1 expressing Cry1C was carried out by: (1) studying horizontal gene transfer (HGT) in Sprague Dawley rats fed transgenic rice for 90 d; (2) examining the effect of Cry1C protein in vitro on digestibility and allergenicity; and (3) studying the changes of intestinal microbiota in rats fed with transgenic rice T1C-1 in acute and subchronic toxicity tests. Sprague Dawley rats were fed a diet containing either 60% GM Bacillus thuringiensis (Bt) rice T1C-1 expressing Cry1C protein, the parental rice Minghui 63, or a basic diet for 90 d. The GM Bt rice T1C-1 showed no evidence of HGT between rats and transgenic rice. Sequence searching of the Cry1C protein showed no homology with known allergens or toxins. Cry1C protein was rapidly degraded in vitro with simulated gastric and intestinal fluids. The expressed Cry1C protein did not induce high levels of specific IgG and IgE antibodies in rats. The intestinal microbiota of rats fed T1C-1 was also analyzed in acute and subchronic toxicity tests by DGGE. Cluster analysis of DGGE profiles revealed significant individual differences in the rats' intestinal microbiota.

Using LC-MS Based Methods for Testing the Digestibility of a Nonpurified Transgenic Membrane Protein in Simulated Gastric Fluid

The digestibility of a nonpurified transgenic membrane protein was determined in pepsin, as part of the food safety evaluation of its resistance to digestion and allergenic potential. Delta-6-desaturase from Saprolegnia diclina, a transmembrane protein expressed in safflower for the production of gamma linolenic acid in the seed, could not be obtained in a pure, native form as normally required for this assay. As a novel approach, the endoplasmic reticulum isolated from immature seeds was digested in simulated gastric fluid (SGF) and the degradation of delta-6-desaturase was selectively followed by SDS-PAGE and targeted LC-MS/MS quantification using stable isotope-labeled peptides as internal standards. The digestion of delta-6-desaturase by SGF was shown to be both rapid and complete. Less than 10% of the initial amount of D6D remained intact after 30 s, and no fragments large enough (>3 kDa) to elicit a type I allergenic response remained after 60 min.

Healthy Ready-to-Eat Expanded Snack with High Nutritional and Antioxidant Value Produced from Whole Amarantin Transgenic Maize and Black Common Bean

The snack foods market is currently demanding healthier products. A ready-to-eat expanded snack with high nutritional and antioxidant value was developed from a mixture (70:30) of whole amarantin transgenic maize (Zea mays L.) and black common bean (Phaseolus vulgaris L.) by optimizing the extrusion process. Extruder operation conditions were: feed moisture content (FMC, 15-25 %, wet basis), barrel temperature (BT, 120-170 °C), and screw speed (SS, 50-240). The desirability numeric method of the response surface methodology (RSM) was applied as the optimization technique over four response variables [expansion ratio (ER), bulk density (BD), hardness (H), antioxidant activity (AoxA)] to obtain maximum ER and AoxA, and minimum BD, and H values. The best combination of extrusion process variables for producing an optimized expanded snack (OES, healthy snack) were: FMC = 15 %/BT = 157 °C/SS = 238 rpm. The OES had ER = 2.86, BD = 0.119 g/cm (3) , H = 1.818 N, and AoxA = 13,681 μmol Trolox equivalent (TE)/100 g, dry weight. The extrusion conditions used to produce the OES increased the AoxA (ORAC: +18 %, ABTS:+20 %) respect to the unprocessed whole grains mixture. A 50 g portion of OES had higher protein content (7.23 vs 2.32 g), total dietary fiber (7.50 vs 1.97 g), total phenolic content (122 vs 47 mg GAE), and AoxA (6626 vs 763 μmol TE), and lower energy (169 vs 264 kcal) than an expanded commercial snack (ECS = Cheetos™). Because of its high content of quality protein, dietary fiber and phenolics, as well as high AoxA and low energy density, the OES could be used for health promotion and chronic disease prevention and as an alternative to the widely available commercial snacks with high caloric content and low nutritional/nutraceutical value.

Safety assessment of foods from genetically modified crops in countries with developing economies

Population growth particularly in countries with developing economies will result in a need to increase food production by 70% by the year 2050. Biotechnology has been utilized to produce genetically modified (GM) crops for insect and weed control with benefits including increased crop yield and will also be used in emerging countries. A multicomponent safety assessment paradigm has been applied to individual GM crops to determine whether they as safe as foods from non-GM crops. This paper reviews methods to assess the safety of foods from GM crops for safe consumption from the first generation of GM crops. The methods can readily be applied to new products developed within country and this paper will emphasize the concept of data portability; that safety data produced in one geographic location is suitable for safety assessment regardless of where it is utilized.

Detailed characterization of Act d 12 and Act d 13 from kiwi seeds: implication in IgE cross-reactivity with peanut and tree nuts

BACKGROUND

Act d 12 (11S globulin) and Act d 13 (2S albumin) are two novel relevant allergens from kiwi seeds that might be useful to improve the diagnostic sensitivity and the management of kiwifruit-allergic patients.

OBJECTIVE

To perform a comprehensive structural and immunological characterization of purified Act d 12 and Act d 13 from kiwi seeds.

METHODS

Sera from 55 well-defined kiwifruit-allergic patients were used. Act d 12 and Act d 13 were purified by chromatographic procedures. Circular dichroism, mass spectrometry, concanavalin A detection, immunoblotting, enzyme-linked immunosorbent assays, basophil activation tests, and IgE-inhibition experiments were used.

RESULTS

Act d 12 and Act d 13 were purified from kiwi seeds to homogeneity by combining size-exclusion, ion-exchange, and RP-HPLC chromatographies. Both purified allergens preserve the structural integrity and display typical features of their homologous counterparts from the 11S globulin and 2S albumin protein families, respectively. These allergens are released from kiwi seeds after oral and gastric digestion of whole kiwifruit, demonstrating their bioavailability after ingestion. The allergens retain the capacity to bind serum IgE from kiwifruit-allergic patients, induce IgE cross-linking in effector-circulating basophils, and display in vitro IgE cross-reactivity with homologous counterparts from peanut and tree nuts.

CONCLUSION

Purified Act d 12 and Act d 13 from kiwi seeds are well-defined molecules involved in in vitro IgE cross-reactivity with peanut and tree nuts. Their inclusion in component-resolved diagnosis of kiwifruit allergy might well contribute to improve the diagnostic sensitivity and the management of kiwifruit-allergic patients.

GT1-7 cell-based cytoxicity screening assay on 96-well microplates as a platform for the safety assessment of genetically modified Gerbera hybrida extracts

In this investigation, a GT1-7 cell-based cytotoxicity screening assay in 96-well microplates was set up. The assay, using propidium iodide fluorescence, was proven to be reliable, with good quality (Z' = 0.51) and low plate-to-plate and day-to-day variations. Further on, a library containing extracts from 227 genetic modification (GM) Gerbera hybrida and 42 Gerbera varieties was screened; however, no differences between them were found. Based on these findings, we propose the use of the current assay within the first-tier screening studies of large collections. Also, these results provide valuable information for GM Gerbera risk-assessment purposes and offer a model for the toxicity cell-based screening of GM crops.

Performing IgE serum testing due to bioinformatics matches in the allergenicity assessment of GM crops

Proteins introduced into genetically modified (GM) organisms through genetic engineering must be evaluated for their potential to cause allergic disease under various national laws and regulations. The Codex Alimentarius Commission guidance document (2003) calls for testing of serum IgE binding to the introduced protein if the gene was from an allergenic source, or the sequence of the transferred protein has >35% identity in any segment of 80 or more amino acids to a known allergen or shares significant short amino acid identities. The Codex guidance recognized that the assessment will evolve based on new scientific knowledge. Arguably, the current criteria are too conservative as discussed in this paper and they do not provide practical guidance on serum testing. The goals of this paper are: (1) to summarize evidence supporting the level of identity that indicates potential risk of cross-reactivity for those with existing allergies; (2) to provide example bioinformatics results and discuss their interpretation using published examples of proteins expressed in transgenic crops; and (3) to discuss key factors of experimental design and methodology for serum IgE tests to minimize the rate of false negative and false positive identification of potential allergens and cross-reactive proteins.

Expression and characterization of the acidic subunit from 11S Amaranth seed protein

Amarantin acidic subunit has the potential to be employed as a functional and a nutraceutical protein. To evaluate both possibilities this protein was produced in recombinant Escherichia coli Origami (DE3) harboring the expression plasmid pET-AC6His. Three different expression factors were assayed: inductor concentration, temperature and time of the amarantin acidic subunit accumulation. The results indicated that a 0.3 mmol/L concentration of isopropyl-beta-D-thiogalactoside, at 37 degrees C and 6 h after induction were favorable for high expression of amarantin acidic subunit, mostly in the form of inclusion bodies. The protein was purified from soluble fraction by immobilized metal affinity chromatography, up to 30 mg amarantin acidic subunit/L Terrific broth culture were obtained. Sucrose density gradient ultracentrifugation analysis of the expressed soluble amarantin acidic subunit revealed that it was assembled in monomers. The expression of the amarantin acidic subunit, together with the one-step purification will facilitate further investigation of this storage protein through site-directed mutagenesis.

Computational analysis of the relationship between allergenicity and digestibility of allergenic proteins in simulated gastric fluid

Background

Safety assessment of genetically modified (GM) food, with regard to allergenic potential of transgene-encoded xenoproteins, typically involves several different methods, evaluation by digestibility being one thereof. However, there are still debates about whether the allergenicity of food allergens is related to their resistance to digestion by the gastric fluid. The disagreements may in part stem from classification of allergens only by their sources, which we believe is inadequate, and the difficulties in achieving identical experimental conditions for studying digestion by simulated gastric fluid (SGF) so that results can be compared. Here, we reclassify allergenic food allergens into alimentary canal-sensitized (ACS) and non-alimentary canal-sensitized (NACS) allergens and use a computational model that simulates gastric fluid digestion to analyze the digestibilities of these two types.

Results

The model presented in this paper is as effective as SGF digestion experiments, but more stable and reproducible. On the basis of this model, food allergens are satisfactorily classified as ACS and NACS types by their pathways for sensitization; the former are relatively resistant to gastric fluid digestion while the later are relatively labile.

Conclusion

The results suggest that it is better to classify allergens into ACS and NACS types when understanding the relationship between their digestibility and allergenicity and the digestibility of a target foreign protein is a parameter for evaluating its allergenicity during safety assessments of GM food.

Endoplasmic reticulum-retention C-terminal sequence enhances production of an 11S seed globulin fromAmaranthus hypochondriacus inPichia pastoris

The methylotrophic yeast Pichia pastoris was used to express an 11S seed globulin from Amaranthus hypochondriacus. Three different plasmids were tested for expression of amarantin. One of them, which included the untranslated regions (UTR) of the full cDNA, failed to express the amarantin under tested conditions, whereas the other plasmids, one without UTR and the other similar but including the endoplasmic reticulum-retention signal KDEL, were able to express the proamarantin in P. pastoris. After 48 h of induction, KDEL-proamarantin had accumulated quite significantly compared to unmodified proamarantin. Different solubilization patterns were also obtained from both proamarantin versions; only soluble protein was obtained from the system that included the KDEL retrieval signal. Protein fractionation was carried out by differential precipitation with ammonium sulfate, and proamarantin purification was performed using an HPLC ion exchange column. The endoplasmic reticulum-retention C-terminal sequence (KDEL retrieval signal), not commonly employed in this heterologous expression system, can therefore be used to enhance accumulation of recalcitrant protein in P. pastoris. The results obtained here also suggest that this expression system is suitable for expression and evaluation of engineered seed globulin proteins.

Assessing Genetically Modified Crops to Minimize the Risk of Increased Food Allergy: A Review

The first genetically modified (GM) crops approved for food use (tomato and soybean) were evaluated for safety by the United States Food and Drug Administration prior to commercial production. Among other factors, those products and all additional GM crops that have been grown commercially have been evaluated for potential increases in allergenic properties using methods that are consistent with the current understanding of food allergens and knowledge regarding the prediction of allergenic activity. Although there have been refinements, the key aspects of the evaluation have not changed. The allergenic properties of the gene donor and the host (recipient) organisms are considered in determining the appropriate testing strategy. The amino acid sequence of the encoded protein is compared to all known allergens to determine whether the protein is a known allergen or is sufficiently similar to any known allergen to indicate an increased probability of allergic cross-reactivity. Stability of the protein in the presence of acid with the stomach protease pepsin is tested as a risk factor for food allergenicity. In vitro or in vivo human IgE binding are tested when appropriate, if the gene donor is an allergen or the sequence of the protein is similar to an allergen. Serum donors and skin test subjects are selected based on their proven allergic responses to the gene donor or to material containing the allergen that was matched in sequence. While some scientists and regulators have suggested using animal models, performing broadly targeted serum IgE testing or extensive pre- or post-market clinical tests, current evidence does not support these tests as being predictive or practical. Based on the evidence to date, the current assessment process has worked well to prevent the unintended introduction of allergens in commercial GM crops.