Beet red food colourant can be produced more sustainably with engineered Yarrowia lipolytica

Synthetic food colourants are widely used in the food industry, but consumer concerns about safety and sustainability are driving a need for natural food-colour alternatives. Betanin, which is extracted from red beetroots, is a commonly used natural red food colour. However, the betanin content of beetroot is very low (~0.2% wet weight), which means that the extraction of betanin is incredibly wasteful in terms of land use, processing costs and vegetable waste. Here we developed a sustainability-driven biotechnological process for producing red beet betalains, namely, betanin and its isomer isobetanin, by engineering the oleaginous yeast Yarrowia lipolytica. Metabolic engineering and fermentation optimization enabled production of 1,271 ± 141 mg l-1 betanin and 55 ± 7 mg l-1 isobetanin in 51 h using glucose as carbon source in controlled fed-batch fermentations. According to a life cycle assessment, at industrial scale (550 t yr-1), our fermentation process would require significantly less land, energy and resources compared with the traditional extraction of betanin from beetroot crops. Finally, we apply techno-economic assessment to show that betanin production by fermentation could be economically feasible in the existing market conditions.

-Improved natural food colorant production in the filamentous fungus Monascus ruber using CRISPR-based engineering

Monascus pigments have various food industry applications and are pharmacologically active. Genome sequencing-based clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology has been implemented to increase pigment production in Monascus. To increase pigment production in M. ruber KACC46666, the CRISPR/Cas9 system was used to introduce mutations in two negative regulator genes (MpigI and MpigI'), among other genes involved in the Monascus pigment biosynthesis pathway. Dual single-guide RNAs were constructed to inactivate MpigI and MpigI'. After CRISPR/Cas9 inactivation, yellow, orange, and red pigment expression in the resulting △MpigI16-7 strain (among several Cas9-mediated mutants studied) was 2.5-, 12.4-, and 18.5-fold, respectively, higher than that in the wild-type strain. This study provides valuable information regarding CRISPR-guided metabolic engineering for natural colorant production.

Ascomycota as a source of natural colorants

In the last few decades, there has been a great demand for natural colorants. Synthetic colorants are known to be easy to produce, are less expensive, and remain stable when subjected to chemical and physical factors. In addition, only small amounts are required to color any material, and unwanted flavors and aromas are not incorporated into the product. Natural colorants present in food, in addition to providing color, also have biological properties and effects that aid in the prevention and cure of many diseases. The main classes of colorants produced by phylum Ascomycota include polyketides and carotenoids. A promising producer of colorants should be able to assimilate a variety of sources of carbon and nitrogen and also exhibit relative stability. The strain should not be pathogenic, and its product should not be toxic. Production processes should also provide the expected color with a good yield through simple extraction methods. Research that seeks new sources of these compounds should continue to seek products of biotechnological origin in order to be competitive with products of synthetic and plant origin. In this review, we will focus on the recent studies on the main producing species, classes, and metabolic pathways of colorants produced by this phylum, historical background, impact of synthetic colorants on human health and the environment, social demand for natural colorants and also an in-depth approach to bioprocesses (influences on production, optimization of bioprocess, extraction, and identification), and limitations and perspectives for the use of fungal-based dyes.

Food colorants metabolized by commensal bacteria promote colitis in mice with dysregulated expression of interleukin-23

Both genetic predisposition and environmental factors appear to play a role in inflammatory bowel disease (IBD) development. Genetic studies in humans have linked the interleukin (IL)-23 signaling pathway with IBD, but the environmental factors contributing to disease have remained elusive. Here, we show that the azo dyes Red 40 and Yellow 6, the most abundant food colorants in the world, can trigger an IBD-like colitis in mice conditionally expressing IL-23, or in two additional animal models in which IL-23 expression was augmented. Increased IL-23 expression led to generation of activated CD4⁺ T cells that expressed interferon-γ and transferred disease to mice exposed to Red 40. Colitis induction was dependent on the commensal microbiota promoting the azo reduction of Red 40 and generation of a metabolite, 1-amino-2-naphthol-6-sulfonate sodium salt. Together these findings suggest that specific food colorants represent novel risk factors for development of colitis in mice with increased IL-23 signaling.

Carrot Anthocyanins Genetics and Genomics: Status and Perspectives to Improve Its Application for the Food Colorant Industry

Purple or black carrots (Daucus carota ssp. sativus var. atrorubens Alef) are characterized by their dark purple- to black-colored roots, owing their appearance to high anthocyanin concentrations. In recent years, there has been increasing interest in the use of black carrot anthocyanins as natural food dyes. Black carrot roots contain large quantities of mono-acylated anthocyanins, which impart a measure of heat-, light- and pH-stability, enhancing the color-stability of food products over their shelf-life. The genetic pathway controlling anthocyanin biosynthesis appears well conserved among land plants; however, different variants of anthocyanin-related genes between cultivars results in tissue-specific accumulations of purple pigments. Thus, broad genetic variations of anthocyanin profile, and tissue-specific distributions in carrot tissues and organs, can be observed, and the ratio of acylated to non-acylated anthocyanins varies significantly in the purple carrot germplasm. Additionally, anthocyanins synthesis can also be influenced by a wide range of external factors, such as abiotic stressors and/or chemical elicitors, directly affecting the anthocyanin yield and stability potential in food and beverage applications. In this study, we critically review and discuss the current knowledge on anthocyanin diversity, genetics and the molecular mechanisms controlling anthocyanin accumulation in carrots. We also provide a view of the current knowledge gaps and advancement needs as regards developing and applying innovative molecular tools to improve the yield, product performance and stability of carrot anthocyanin for use as a natural food colorant.

Spectroscopic and molecular docking studies on the interaction of phycocyanobilin with peptide moieties of C-phycocyanin

The binding of C-phycocyanin (CPC), a light harvesting pigment with phycocyanobilin (PCB), a chromophore is instrumental for the coloration and bioactivity. In this study, structure-mediated color changes of CPC from Spirulina platensis during various enzymatic hydrolysis was investigated based on UV-visible, circular dichroism, infra-red, fluorescence, mass spectrometry, and molecular docking. CPC was hydrolyzed using 7.09 U/mg protein of each enzyme at their optimal hydrolytic conditions for 3 h as follows: papain (pH 6.6, 60 °C), dispase (pH 6.6, 50 °C), and trypsin (pH 7.8, 37 °C). The degree of hydrolysis was in the order of papain (28.4%) > dispase (20.8%) > trypsin (7.3%). The sequence of color degradation rate and total color difference (ΔE) are dispase (82.9% and 40.37), papain (72.4% and 24.70), and trypsin (58.7% and 25.43). The hydrolyzed peptides were of diverse sequence length ranging from 8 to 9 residues (papain), 7-12 residues (dispase), and 9-63 residues (trypsin). Molecular docking studies showed that key amino acid residues in the peptides interacting with chromophore. Amino acid residues such as Arg86, Asp87, Tyr97, Asp152, Phe164, Ala167, and Val171 are crucial in hydrogen bonding interaction. These results indicate that the color properties of CPC might associate with chromopeptide sequences and their non-covalent interactions.

The biotechnology (genetic transformation and molecular biology) of Bixa orellana L. (achiote)

Genetic transformation allows for greater bixin or norbixin production in achiote. Knowledge of genes that control the biosynthesis of these important secondary metabolites will allow for targeted amplification in transgenic plants. Annatto is a natural dye or coloring agent derived from the seeds, or their arils, of achiote (Bixa orellana L.), and is commercially known as E160b. The main active component of annatto dye is water-insoluble bixin, although water-soluble norbixin also has commercial applications. Relative to other antioxidants, bixin is light- and temperature stable and is thus safe for human consumption. Bixin is, therefore, widely applied as a dye and as an antioxidant in the medico-pharmaceutical, food, cosmetic, and dye industries. Even though bixin has also been isolated from leaves and bark, yield is lower than from seeds. More biotechnology-based research of this industrial and medicinal plant is needed. Building on provisional genetic transformation studies, it would be advantageous to transform genes that could result in greater bixin or norbixin production. Reliable protocols for the extraction of bixin and norbixin, as well as deeper knowledge of the genes that control the biosynthesis of these important secondary metabolites will allow for targeted amplification in transgenic plants.

Analyses of Monascus pigment secretion and cellular morphology in non-ionic surfactant micelle aqueous solution

Monascus pigments produced by Monascus spp. are widely used as natural food colourants. Extractive fermentation technology can facilitate the secretion of intracellular Monascus pigments into extracellular non-ionic surfactant micelle aqueous solution, so as to avoid the feedback inhibition and decomposition. In this study, behaviour of the trans-membrane secretion of Monascus pigments was investigated using morphological and spectroscopic analyses. Laser scanning confocal microscopy (LSCM) traced that pigment secretion occurred through rapid trans-membrane permeation in 4 min, with a simultaneous conversion in pigment characteristics. Approximately 50% of intracellular pigments (AU470 ) extracted to extracellular broth with 40 g l-1 Triton X-100, indicating the capacity for pigment extraction was limited by the saturation concentrations of surfactant. Scanning electron microscope (SEM) and transmission electron microscope (TEM) imaging showed some damage in the cell wall but an intact cell membrane with a slightly increased mycelial diameter. However, the physiological properties of the cell membrane, including integrity, fluorescence intensity and permeability, were altered. A diagram was provided to demonstrate the behaviour of Monascus pigment secretion induced by Triton X-100. This study lays a foundation for the further investigation of Monascus pigment metabolism and secretion in extractive fermentation.

Inclusion of Palmaria palmata (red seaweed) in Atlantic salmon diets: effects on the quality, shelf-life parameters and sensory properties of fresh and cooked salmon fillets

BACKGROUND

The use of Palmaria palmata (PP) as a natural ingredient in farmed Atlantic salmon diets was investigated. The effect of salmon diet supplementation with P. palmata (0, 5, 10 and 15%) or synthetic astaxanthin (positive control, PC) for 16 weeks pre-slaughter on quality indices of fresh salmon fillets was examined. The susceptibility of salmon fillets/homogenates to oxidative stress conditions was also measured.

RESULTS

In salmon fillets stored in modified atmosphere packs (60% N2 /40% CO2 ) for up to 15 days at 4 °C, P. palmata increased surface -a* (greenness) and b* (yellowness) values in a dose-dependent manner, resulting in a final yellow/orange flesh colour. In general, the dietary addition of P. palmata had no effect on pH, lipid oxidation (fresh, cooked and fillet homogenates) and microbiological status. 'Eating quality' sensory descriptors (texture, odour and oxidation flavour) in cooked salmon fillets were not influenced by dietary P. palmata. Salmon fed 5% PP showed increased overall acceptability compared with those fed PC and 0% PP.

CONCLUSION

Dietary P. palmata was ineffective at providing red coloration in salmon fillets, but pigment deposition enhanced fillets with a yellow/orange colour. Carotenoids from P. palmata may prove to be a natural pigment alternative to canthaxanthin in salmon feeds.

Filamentous fungi are large-scale producers of pigments and colorants for the food industry

With globalization in the research trends, healthier life styles, and the growing market for the natural food colorants in the economically fast-growing countries all over the world, filamentous fungi are being investigated as readily available sources of chemically diverse colorants. With two selected examples, polyketide-Monascus-like pigments from the new fungal production strains, and the promising and yet unexplored hydroxy-anthraquinoid colorants, the present review highlights exciting recent findings, which may pave the way for alternative and/or additional biotechnological processes for the industrial production of natural food colorants of improved functionality. As an additional aspect, marine fungi are discussed as potential sources of novel pigments of numerous color hues and atypical chemical structures.

Purification of the photosynthetic pigment C-phycocyanin from heterotrophic Galdieria sulphuraria

BACKGROUND

The phycobiliprotein C-phycocyanin (C-PC) is used in cosmetics, diagnostics and foods and also as a nutraceutical or biopharmaceutical. It is produced in the cyanobacterium Arthrospira platensis grown phototrophically in open cultures. C-PC may alternatively be produced heterotrophically in the unicellular rhodophyte Galdieria sulphuraria at higher productivities and under improved hygienic standards if it can be purified as efficiently as C-PC from A. platensis.

RESULTS

Ammonium sulfate fractionation, aqueous two-phase extraction, tangential flow ultrafiltration and anion exchange chromatography were evaluated with respect to the purification of C-PC from G. sulphuraria extracts. Galdieria sulphuraria C-PC showed similar properties to those described for cyanobacterial C-PC with respect to separation by all methodologies. The presence of micelles in G. sulphuraria extracts influenced the different procedures. Only chromatography was able to separate C-PC from a second phycobiliprotein, allophycocyanin.

CONCLUSION

C-PC from heterotrophic G. sulphuraria shows similar properties to cyanobacterial C-PC and can be purified to the same standards, despite initial C-PC concentrations being low and impurity concentrations high in G. sulphuraria extracts.

Optical spectroscopic exploration of binding of Cochineal Red A with two homologous serum albumins

Cochineal Red A is a negatively charged synthetic azo food colorant and a potential carcinogen. We present here the study of binding of Cochineal Red A with two homologous serum albumins, human (HSA) and bovine (BSA), in aqueous pH 7.4 buffer by optical spectroscopic techniques. Protein intrinsic fluorescence quenching by Cochineal Red A occurs through ground-state static interaction and its binding with BSA is stronger than with HSA. The magnitudes of thermodynamic parameters suggest that dye binding occurs principally via electrostatic complexation. Site-marker competitive binding shows that Cochineal Red A binds primarily to site I of serum albumins. Circular dichroic spectra indicate that dye binding results in some conformational modification of serum albumins. Increased ionic strength of the medium results in lowering of binding. This study provides an important insight into possible means of removal of dye toxicity.

Colour evaluation of a phycobiliprotein-rich extract obtained from Nostoc PCC9205 in acidic solutions and yogurt

BACKGROUND

Phycobiliproteins are coloured proteins produced by cyanobacteria, which have several applications because of their colour properties. However, there is no available information about the colour stability of phycobiliproteins from Nostoc sp. in food systems. The aim of this work was to study the colour stability of a purple-coloured phycobiliprotein-rich extract from the cyanobacterium Nostoc PCC9205 in acidic solutions and yogurt.

RESULTS

Variations of pH for Nostoc PCC9205 extract have shown stability for the L* (lightness) and a* (redness) indexes in the range 1.0-7.0. The b* index (blueness), however, increased at pH values below 4.0, indicating loss of the blue colour. The Nostoc PCC9205 extract was used as colorant in yogurt (pH 4.17) stored for 60 days. Instrumental colour analysis showed no changes for the L* and a* indexes during storage, whereas the b* index changed after 20 days of storage. A multiple comparison test showed colour instability after 20 days of storage. A hedonic scale test performed on the 60th day of storage showed acceptability of the product.

CONCLUSIONS

The red component of the phycobiliprotein-rich extract from Nostoc PCC9205 presented an improved stability in acidic media and yogurt compared with the blue component of this extract.

Computerized screening for novel producers of Monascus-like food pigments in Penicillium species

Monascus pigments have been used as natural food colorants in Asia for centuries. They are not authorized for use in the European Union and the United States mainly due to the risk of coproduction of the mycotoxin citrinin by Monascus spp. In the present study, we screened for novel producers of Monascus-like pigments from ascomycetous filamentous fungi belonging to Penicillium subgenus Biverticillium that are not reported to produce citrinin or any other known mycotoxins. The screening was carried out using the X-hitting algorithm as a tool to quickly screen through chromatographic sample data files of 22 different Penicillium extracts with 12 Monascus pigment extracts as controls. The algorithm searched for the most similar UV-vis spectra of the metabolites (cross hits) present in the pigment extracts to those of the selected reference metabolites viz. monascin, rubropunctatin, rubropunctamine, and citrinin. The cross hits were then manually identified on the basis of their UV-vis and mass spectra. X-hitting was found to be a good tool in the rapid screening of crude pigment extracts. Monascus pigments were discovered in the extracts of two closely related species of Penicillium that were only distantly related to the genus Monascus. Monascorubrin, xanthomonasin A, and threonine derivatives of rubropunctatin were identified in the extract of Penicillium aculeatum IBT 14263, and monascorubrin was identified in the extract of Penicillium pinophilum IBT 13104. None of the tested Penicillium extracts showed the presence of citrinin. Thus, the present study brought out two novel promising sources of yellow, orange, and purple-red Monascus-like food pigments in the species of Penicillia that do not produce citrinin and opened the door to look for several more new promising sources of natural food colorants in the species of Penicillia.

Construction of a replacement vector to disrupt pksCT gene for the mycotoxin citrinin biosynthesis in Monascus aurantiacus and maintain food red pigment production

More and more people pay attention to citrinin produced by Monascus, which has nephrotoxic activity in mammals. It was reported that pksCT gene is responsible for citrinin biosynthesis in Monascus purpureus. In this paper, two DNA fragments in both ends of pksCT were amplified by genomic PCR from fourteen Monascus spp. strains. The PCR products were gained from all of the strains. It is suggested that pksCT gene was highly conserved in different citrinin-producing Monascus strains. A pksCT-replacement vector (pHD106) was constructed to disrupt pksCT with a hygromycin resistance gene as the selection marker, and was transformed into M. aurantiacus Li AS3.4384. Three transformants (M. aurantiacus PHDS18, PHDS26, PHDS31) were selected from transformant selective plates. The targeting fragment D was gained by genomic PCR from PHDS18 and PHDS26 except PHDS31. The expressing citrinin capacities of PHDS26 was decreased by about 98%, while PHDS18 was reserved the high capacity of producing citrinin, after 10 days of growth on YM medium. The results indicated that PHDS26 is a pksCT-disrupted strain. There are maybe other genes besides pksCT responsible for citrinin biosynthesis in M. aurantiacus. It is the effective way to solve the problem of citrinin in M. aurantiacus products by constructing replacement vectors to disrupt the genes responsible for citrinin biosynthesis to reduce the capacity of expressing citrinin.

Production of superoxide radical in reductive metabolism of a synthetic food-coloring agent, indigocarmine, and related compounds

Indigocarmine, which is widely used as a synthetic colouring agent for foods and cosmetics in many countries, was reduced to its leuco form and decolorized by rat liver microsomes with NADPH under anaerobic conditions. The reductase activity was enhanced in liver microsomes of phenobarbital-treated rats, and inhibited by diphenyliodonium chloride, a NADPH-cytochrome P450 reductase (P450 reductase) inhibitor, but was not inhibited by SKF 525-A or carbon monoxide. Indigocarmine reductase activity was exhibited by purified rat P450 reductase. In contrast, when indigocarmine was incubated with rat liver microsomes and NADPH under aerobic conditions, superoxide radical was produced and its production was inhibited by superoxide dismutase and diphenyliodonium chloride. When indigocarmine was incubated with purified rat P450 reductase in the presence of NADPH, superoxide radical production was enhanced 17.7-fold (similar to the enhancement of indigocarmine-reducing ability) as compared with that of rat liver microsomes. A decrease of one molecule of NADPH was accompanied with formation of about two molecules of superoxide radical. P450 reductase exhibited little reductase activity towards indigo and tetrabromoindigo, which also afforded little superoxide radical under aerobic conditions. These results indicate that indigocarmine is reduced by P450 reductase to its leuco form, and superoxide radical is produced by autoxidation of the leuco form, through a mechanism known as futile redox cycling.

Synthetic organic food colouring agents and their degraded products: effects on human and rat cholinesterases

Most synthetic coloured additives are carcinogenic; teratogenic and cause allergic reactions. In this study, the effects of synthetic azo dyes (sunset yellow FCF and carmoisine), as well as their degraded products (sulphanilic acid and naphthionic acid), on both true and pseudo-cholinesterases (ChEs) are studied. The results indicate that the synthetic azo dyes and their degraded products inhibit both human true and pseudo-ChE activities in vitro. The concentration of coloured additive that cause 50% inhibition (IC50) and enzyme inhibitor dissociation constant (Ki) show that sunset yellow FCF produces greater inhibition of both true and pseudo-ChEs than does carmoisine and sulphanilic acid, while naphthionic acid produces greater inhibition of pseudo-ChE only. Ki indicates that the affinity of sulphanilic acid for both true and pseudo-ChEs is higher than the other three inhibitors. Inhibition of both true and pseudo-ChEs by sunset yellow FCF is of mixed (competitive and non-competitive) type, but carmoisine and sulphanilic acid are non-competitive. Naphthionic acid produces a competitive inhibition kinetic with plasma ChE only. This inhibition is abolished by dialysis, indicating that their effects are reversible. The effects of sunset yellow FCF, carmoisine, sulphanilic acid and naphthionic acid on rat true and pseudo-ChEs are investigated. The data clearly show that there is a significant decrease in enzyme activity. Sulphanilic acid and sunset yellow FCF are the most potent in vivo inhibitors of true ChE and pseudo-ChE, respectively.

[Study on the production of citrinin by Monascus strains used in food industry]

In order to screen strains with less or nearly no production of citrinin, thirty-five Monascus strains used in food industry were selected to investigate the effect of cultivation condition and the medium composition on citrinin production. The results from the study indicated that all strains produced citrinin on the rice with the levels ranging from 0.28 to 2458.80 mg/kg (201.60 mg/kg for the average and 61.99 mg/kg for the median, respectively), while 30 strains (85.71%) yielded this toxin on the submerged culture with the concentration between 0.09 and 55.65 mg/kg (11.99 mg/kg for the average and 3.51 mg/kg for the median, respectively). Therefore, citrinin production in rice in this study was higher than that in the liquid. In addition, the red pigment production in rice was 3-509 (average 93) times higher than that in the liquid. One strain with the highest color value (1134 U/g) but lower citrinin production in rice was obtained. These results suggested that it is necessary to make the safety evaluation of microorganisms for the production of foods and food ingredients, to investigate the ability of citrinin production by Monascus strains preserved by either the food manufacturer or the national culture collection units and, to survey the citrinin contamination in Monascus products countrywide. It is urgent for China to establish the tolerance limit of citrinin in foods fermented by Monascus species.

Microbial populations associated with treatment of an industrial dye effluent in an anaerobic baffled reactor

Fluorescent in situ hybridization (FISH) using 16S and 23S rRNA-targeted probes together with construction of an archaeal 16S ribosomal DNA (rDNA) clone library was used to characterize the microbial populations of an anaerobic baffled reactor successfully treating industrial dye waste. Wastewater produced during the manufacture of food dyes containing several different azo and other dye compounds was decolorized and degraded under sulfidogenic and methanogenic conditions. Use of molecular methods to describe microbial populations showed that a diverse group of Bacteria and Archaea was involved in this treatment process. FISH enumeration showed that members of the gamma subclass of the class Proteobacteria and bacteria in the Cytophaga-Flexibacter-Bacteroides phylum, together with sulfate-reducing bacteria, were prominent members of a mixed bacterial population. A combination of FISH probing and analysis of 98 archaeal 16S rDNA clone inserts revealed that together with the bacterial population, a methanogenic population dominated by Methanosaeta species and containing species of Methanobacterium and Methanospirillum and a relatively unstudied methanogen, Methanomethylovorans hollandica, contributed to successful anaerobic treatment of the industrial waste. We suggest that sulfate reducers, or more accurately sulfidogenic bacteria, together with M. hollandica contribute considerably to the treatment process through metabolism of dye-associated sulfonate groups and subsequent conversion of sulfur compounds to carbon dioxide and methane.

Analysis of the metabolites of the sodium salt of 6-hydroxy-5-(phenylazo)-2-naphthalenesulfonic acid in Sprague-Dawley rat urine

The sodium salt of 6-hydroxy-5-(phenylazo)-2-naphthalenesulfonic acid (SS-AN), which is a subsidiary color present in Food Yellow No. 5 [Sunset Yellow FCF, disodium salt of 6-hydroxy-5-(4-sulfophenylazo)-2-naphthalenesulfonic acid], was orally administered to Sprague-Dawley rats. Metabolite A, metabolite B, and unaltered SS-AN were detected as colored metabolites in the rat urine. Analysis of the chemical structures showed that metabolite A (major peak) was 6-hydroxy-5-(4-sulfooxyphenylazo)-2-naphthalenesulfonic acid, the sulfuric acid conjugate of SS-AN, and metabolite B (minor peak) was 6-hydroxy-5-(4-hydroxyphenylazo)-2-naphthalenesulfonic acid (SS-PAP), which is a derivative of metabolite A without the sulfuric acid. The colorless metabolites p-aminophenol, o-aminophenol, and aniline present in the urine were analyzed by liquid chromatography-mass spectrometry. The orally administered SS-AN had been metabolized to the colorless metabolites (p-aminophenol 45.3%, o-aminophenol 9.4%, aniline 0.4%) in the 24-h urine samples. Analysis of the colored metabolites by high-performance liquid chromatography with detection at 482 nm indicated the presence of metabolite A (0.29%), SS-PAP (0.01%), and SS-AN (0.02%) were detected in the 24-h urine samples. Approximately 56% of SS-AN was excreted into the urine and the rest is probably excreted into feces.

The case of the red lingerie - chromhidrosis revisited

Chromhidrosis or the production of coloured sweat is a rare clinical finding. A 26-year-old female presented with marked pink staining of her uniform and lingerie. Extractions of clothing, skin surface samples, eccrine sebum, urine and a fast food product were spectrophotometrically analysed to identify the pink staining pigment. Three water-soluble colouring agents have been identified. An eccrine route of excretion probably produced chromhidrosis. An overview is presented.

Mutagenicity of commercial Monascus fermentation products and the role of citrinin contamination

Pigments produced as secondary metabolites by various isolates of moulds belonging to the genus Monascus have been used traditionally as colorants in Oriental food. Modern food industry has rediscovered these moulds as promising source for natural colorants. However, recent studies evidence that one of the secondary metabolites produced by Monascus is identical in structure to the mycotoxin citrinin. Thus, a sensitive HPLC method was developed to analyse these food colorants for contamination with citrinin. The mycotoxin could be detected in all the commercial Monascus samples at concentrations varying between 0.2 to 17.1 microg/g. In addition, the mutagenicity of commercial Monascus samples applying Salmonella-microsome assay and Salmonella-hepatocyte-assay was investigated and compared to the results obtained with citrinin. Citrinin and two Monascus extracts induced a positive dose depending mutagenic response in the Salmonella-hepatocyte-assay applying strain TA-98. However, no mutagenicity could be detected in the Salmonella-microsome assay, neither with nor without S9-mix, for citrinin and Monascus extracts, applying TA-98, TA-100, TA-1535, TA-1538 and TA-97. These findings provide further evidence that citrinin requires complex cellular biotransformation to exert mutagenicity.

Isolation and identification of a major urinary canthaxanthin metabolite in rats

The urinary metabolic pattern after administration of the radiolabeled non-provitamin A carotenoid canthaxanthin was investigated in rats. In the rather complex HPLC urinary metabolic pattern a fraction was found which was conjugated. Deconjugation of the polar conjugates with glusulase, purification of the metabolite with HPLC and identification with GC-MS and NMR revealed that it was 3-hydroxy-4-oxo-7,8-dihydro-beta-ionone. This structure was confirmed by comparisons with HPLC retention times, UV/VIS- and NMR-spectroscopy and GC-MS of the synthesized compound.

Production of food related colorants by culture of plant cells. The case of betalains

Betalains are vacuole pigments produced solely by Caryophyllales plants and few superior fungi. For many years, betalains have been used as food colorants. The aim of the present chapter is to present relevant aspects related to betalains characteristics and feasibility of their industrial production in bioreactors.

Reductive and hydrolytic activities of enteric bacteria on food colours

Reductive and hydrolytic activities on two food colours namely metanil yellow and indigo carmine by different strains of enteric bacteria were evaluated. Enteric bacteria possessed both reductive and hydrolytic capabilities which depended upon the incubation period and the type of strain. In certain bacterial strains, (Escherichia coli and Vibrio sp.), reductive activity was visible after 3 hr. Other enteric strains showed an increasing activity right from the beginning of incubation. Enterobacter cloacae appeared to be producing maximum reductive capability followed by Enterobacter aerogenes and E. coli. Even enteric bacterial strains demonstrated a good response in obtaining hydrolytic activity of indigo carmine during incubation upto 10 hr, establishing the fact that the gut microflora may cause health problem to consumers.

Metabolic activation and inactivation of metanil yellow and orange II in the Salmonella typhimurium his-reversion assay

Among a variety of experimental protocols used, the combined use of 0.5% dextrose in bottom agar and 1 micromol of flavin mononucleotide (FMN) in preincubation mixtures without fraction S9 mix resulted in the highest level of induced Salmonella typhimurium his reversions with both dyes metanil yellow and orange 11 with strain TA100. Strain TA98 yielded notably lower levels of reversions under the same conditions. The presence of uninduced hamster liver S9 fraction resulted in a weak mutagenic response while Aroclor 1254-induced rat liver S9 fraction resulted in the complete absence of mutagenicity with both strains and with both dyes.

Bio-metabolic disposition of metanil yellow, orange II and their blend by caecal microflora of rats

Caecal microflora were employed to study the degradation pattern, with time course of Metanil yellow and Orange II-two extensively used non-permitted food colours. Metanil yellow and Orange II showed the respective Degradation Index 50 (DI 50) values of 369 and 288 min. However, the blend of Metanil yellow and Orange II (1:1) resulted in the D1 50.value of 288 min. Metanil yellow, Orange II and their blend were resolved into respective metabolites in different solvent systems.

The SCID-hu mouse as a tool in immunotoxicological risk assessment: effects of 2-acetyl-4(5)-tetrahydroxybutyl-imidazole (THI) and di-n-butyltin dichloride (DBTC) on the human thymus in SCID-hu mice

SCID mice engrafted with human fetal thymus and liver tissue fragments (SCID-hu mice) are currently considered as a new tool in human immunotoxicological risk assessment. Testing of various immunotoxicants exerting thymotoxicity via different intrathymic target cell types is necessary for validation of this model. Therefore, SCID-hu mice were exposed to 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)-imidazole (THI), the immunotoxic component in the food additive, Caramel Colour III, or the organotin compound, di-n-butyltin dichloride (DBTC). Histopathological examination of the human thymus grafts of SCID-hu mice either exposed to THI or to DBTC showed a reduction in the relative size of the thymus cortex, an effect also described in rodents. These results indicate that the human thymus is a target for the immunotoxic action of both THI and DBTC. In addition, they indicate the promising potential of the SCID-hu mouse model as a tool for human immunotoxicological risk assessment.

A urine collection system for studying the excretion of xenobiotics from Dungeness crabs

A technique is described for collecting urine from the Dungeness crab, Cancer magister (Dana), a commercially important seafood and an indicator species of aquatic pollution. The technique has been modified from previously published methods to study the role of urinary excretion in the elimination of lipophilic pollutants by the Dungeness crab. The improved urine collection system uses chemically resistant and nonreactive materials that are better suited to pharmacological and toxicological studies than those used in previous methods. The improved method was tested by injecting a vital dye into catheterized Dungeness crabs and by measuring urine flows for 10 days. This technique can be used to determine the urinary excretion of xenobiotics and facilitate the characterization of chemicals and their metabolites accumulated by crabs.

Bio-metabolism of green S and indigo carmine through caecal microflora of rats

Bio-metabolism of two permitted food colours viz., Green S and Indigo Carmine, through caecal microflora of rats was investigated. Incubation of Green S with caecal flora resulted in one coloured and two fluorescent metabolites with the corresponding Rf values of 0.83, 0.33, 0.22, respectively. Indigo carmine was metabolized by caecal microflora to four [corrected] fluorescent metabolites with Rf values of 0.09, 0.27, 0.5 and 0.72. The DI 50 value of Green S was considerably higher (456 min) as compared to that of Indigo carmine (54 min). These results suggest that Green S and Indigo carmine are biotransformed to a variety of metabolites by rat caecal microflora.

Microbiological research on soft drinks: discolouring of natural-flavoured products

The results of experiments testing the effects of yeasts, sunlight, and temperature on the food dyes tartrazine, ponceau 4R, indigotin and azorubin (used for colouring ginger soft drink) are reported. Light was found to exert a greater influence than heat, and yeasts growth hastened colour degradation. Yeasts assimilated to varying extent the colouring compounds and, when failing to do it, showed a certain power of adsorption by the no longer viable cells.

Determination of total non-sulphonated aromatic amines in tartrazine, sunset yellow FCF and allura red by reduction and derivatization followed by high-performance liquid chromatography

Free and bound non-sulphonated aromatic amines (NSAA) are determined in the food colours tartrazine, sunset yellow FCF and allura red. After reduction of the bound amines with sodium dithionite, the NSAA are extracted into chloroform, then transferred to aqueous acid solution, diazotized with sodium nitrite and coupled with 2-naphthol-3,6-disulphonic acid, disodium salt (R-salt). Reversed-phase ion-pair liquid chromatography and an absorbance detector at 512 nm are used to analyse the coloured derivatives. Samples of dyes were spiked with known amounts of aniline, 1-naphthylamine, 2- and 4-aminobiphenyl, 4-aminoazobenzene, benzidine, p-cresidine or 4-nitro-p-cresidine bound to R-salt. Recoveries averaged 90% in tartrazine, 65% in sunset yellow FCF and 71% in allura red. Detection limits ranged between 2 and 32 ng/g. A survey of 24 commercial samples revealed levels up to 520 micrograms/g total NSAA. The majority of NSAA are bound to the coupling compound during the manufacturing process and less than 7% remain as free amines in the dye.

Identification of [14C]carmoisine metabolites in bacterial suspension of rat faeces

An in vitro system consisting of a bacterial suspension of human or rat faecal microflora brought about the biological reduction of the red azo dye [14C]carmoisine to 1-naphthyl-amine-4-sulphonic acid (NA) and 2-amino-1-naphthol-4-sulphonic acid (ANA). These metabolites have been unequivocally identified by radio-HPLC, spectroscopic methods, dilution with cold authentic standards and evidence that the specific activity of the diluted compounds remained constant throughout repeated crystallization, acetylation and purification. The results clearly indicated that samples derived from anaerobic incubations have to be processed for analysis in the complete absence of oxygen. In the presence of oxygen, the formation of a complex pattern of compounds in addition to NA was observed as a consequence of the chemical decomposition of ANA.

Long-term toxicity study of amaranth in rats using animals exposed in utero

Groups of 90 (control) and 54 (treated) rats of each sex were given amaranth in their diet to provide daily intakes of 0 (control), 50, 250 or 1250 mg/kg for 111 wk (male) and 112 wk (female) after weaning. The rats had also been exposed to the same dose levels in utero, and their parents were exposed for 60 days before mating. The colouring had no adverse effects on fertility, haematological parameters, serum chemistry or incidence of tumours. All treated animals showed contamination of the fur and red colouring of the faeces and at the high dose only the faecal pellets were poorly formed. Rats in the high-dose group produced more pups, and the average pup weight was lower than that of the controls. Rats of the F1 generation given the highest dose level were slightly lighter than the controls despite a small increase in food and water intake. Both sexes given the highest dose level and males given 250 mg/kg/day had increased caecal weight. High-dose females excreted more protein in the urine after 18 months and on histopathological examination females in all treated groups showed an increased incidence of renal calcification and pelvic epithelial hyperplasia with degenerative changes. It is concluded that amaranth fed to rats at dose levels of up to 1250 mg/kg/day in the diet did not have any carcinogenic effect. However, because of the effect on the kidneys of the females it was not possible to establish a no-untoward-effect level in this study.

Metabolic disposition of 14C-labelled carmoisine in the rat, mouse and guinea-pig

The absorption, metabolism and excretion of 14C-labelled carmoisine has been studied in the rat, mouse and guinea-pig. Following administration of a single oral dose of either 0.5 or 50 mg/kg body weight, substantially all of the dose was recovered in the excreta within 72 hr, mainly in the faeces. Although the urinary excretion of radioactivity was similar in the rat and the mouse, the proportion of the radioactivity found in the urine of the guinea-pig was significantly greater than that of the other species at both dose levels. Pretreating male rats with unlabelled colouring in the diet (0.05%, w/w) for 28 days prior to dosing with 14C-labelled colouring had no effect on the route of excretion or the time taken to eliminate the majority of the labelled dose. Following a single oral dose of 14C-labelled colouring to previously untreated rats, mice and guinea-pigs or to rats pretreated as above, no marked accumulation of radioactivity in any tissue was found. Pregnant rats eliminated a single oral dose of 14C-labelled colouring at a similar rate to non-pregnant females, and the concentration of radioactivity in the foetuses was similar to that in the other tissues. Naphthionic acid was the major urinary metabolite in all three species. In the rat and mouse, most of the remaining radioactivity co-chromatographed with 2-amino-1-naphthol-4-sulphonic acid (2-ANS), but in the guinea-pig radioactivity also co-chromatographed with 1,2-naphthoquinone-4-sulphonate (1,2-NQS). Only a trace amount of unchanged carmoisine was detected in the urine of the species examined. Naphthionic acid was also found in the faeces of all three species, but neither carmoisine, 2-ANS or 1,2-NQS was detected. At least five other radioactive metabolites were found in the faecal extracts of all three species, including a substantial amount of a compound with chromatographic properties similar to those of a trace metabolite in the urine. Two of the faecal metabolites were hydrolysed by beta-glucuronidase and sulphatase treatment. In studies on the absorption of carmoisine at concentrations of 50, 500 or 5000 ppm from isolated intestinal loops, no significant absorption was detected in the rat, mouse or guinea-pig.

The use of continuous flow systems for studying the metabolic activity of the hindgut microflora in vitro

To investigate the involvement of bacterial enzyme activities in the biotransformation of xenobiotic compounds, we have developed a simulation of the rat hindgut microflora in vitro. This mixed bacterial population exhibits many similarities to the native rat flora, and the diversity of bacterial species and the activity of a number of hydrolytic and reductive enzymes (e.g. azoreductase, beta-glucosidase, beta-glucuronidase, nitrate reductase and nitroreductase) are reproduced in the culture at levels similar to those found in the large intestine. The flora have been found to respond to an anutrient (cyclamate) or to host products (bile acids) with changes in enzyme activity, and to metabolize the azo dye Brown HT to metabolites qualitatively similar to those found in the faeces after oral administration to the rat. The experiments demonstrate that the bacterial population of the large intestine of the rat may be successfully cultured in vitro and provides and alternative to animal studies for the investigation of foreign compound metabolism by the flora.

Brain uptake of a food dye, erythrosin B, prevented by plasma protein binding

Although food colors have been held responsible for several behavioral disorders and do affect neuronal function when directly applied, there is no information on whether significant quantities of the dyes appear in the brain after consumption or parenteral administration. [14C]erythrosin B was administered directly into the circulation of mature rats and radioactivity was measured thereafter in brain regions at several times. Although insignificant parenchymal radioactivity was detected in brains perfused with dye in whole blood, significant concentrations of [14C]erythrosin B were detected in all brain regions when perfused with protein-free Ringers, as predicted from the octanol-water partition coefficient of the dye. Thus, significant brain uptake of intravascular dye is normally prevented by its binding to plasma protein (greater than 99% bound) and by the blood-brain barrier impermeability to the dye-protein complex. Sensitivity to food dyes such as erythrosin B in some individuals may reflect altered plasma protein binding capacity, which can vary with age and disease.

Mutagenicity studies of urine and faecal samples from rats treated orally with the food colourings Brown FK and Red 2G

Urine and faecal extracts from rats given Brown FK or Red 2G orally (800 mg/kg body weight) were investigated for mutagenicity. Extracts were subjected to liquid fluctuation and plate incorporation assays with Salmonella typhimurium strains TA98 and TA100 in the presence and absence of liver microsomes and/or a beta-glucuronidase-sulphatase preparation. Urine from Red 2G-treated rats only exhibited direct activity when coloured fractions from polyamide-column concentrates were tested with TA100. All other urines, as well as aqueous and ether faecal extracts from animals receiving either colouring, were no more mutagenic than the respective control extracts obtained from the same animals prior to dosing.

Mutagenic activity at different stages of an industrial ammonia caramel process detected in Salmonella typhimurium TA100 following pre-incubation

Mutagenic activity of a commercial ammonia caramel colouring was demonstrated in Salmonella typhimurium TA100 without metabolic activation. The activity in strain TA100 was increased using a 10-min pre-incubation, and a clear dose-response relationship was seen using this method. Investigation of samples taken from the different stages in the industrial process showed a constant level of mutagenic activity in samples from the middle to the end of the heating process with a steep increase in the sample taken after the end of heating. No mutagenic activity was seen in assays with S. typhimurium strains TA1535 and TA98.

The metabolic disposition of 14C-labelled Ponceau 4R in the rat, mouse and guinea-pig

The absorption, metabolism and excretion of 14C-labelled Ponceau 4R has been studied in the rat, mouse and guinea-pig. Following administration of a single oral dose of 0.5 or 50 mg/kg body weight substantially all of the dose was excreted in the urine and faeces within 72 hr, with the majority being accounted for in the faeces. In all three species, naphthionic acid was the major urinary metabolite, whereas in the faeces naphthionic acid, 7-hydroxy-8-aminonaphthalene-1,3-disulphonic acid and unchanged dye were found. Pretreating male rats with unlabelled Ponceau 4R in the diet (50 mg/kg/day) for 28 days prior to dosing with the 14C-labelled colouring had no effect on the route of excretion or the time taken to eliminate the majority of the label. Following a single dose of 14C-labelled colouring to previously untreated rats, mice and guinea-pigs or to rats pretreated as above, no marked accumulation of radioactivity in any tissue was found, although tissue levels of radioactivity at 72 hr after dosing were higher in the pretreated rats than in those that were not pretreated. Pregnant rats eliminated a single oral dose of 14C-labelled colouring at a similar rate to non-pregnant females; however, some retention of radioactivity in the foetuses was found. In studies of absorption from isolated loops of small intestine containing 50, 500 or 5000 ppm Ponceau 4R, no significant absorption was detected in rats, but some absorption was seen in mice at the lowest concentration, and in the guinea-pig at the two higher concentrations.

Placental transfer and tissue localization of [14C]carmoisine in the pregnant rat

Pregnant Sprague-Dawley rats received [14C]Carmoisine (200 mg/kg; 25 microCi) by gavage, on days 16-19 of gestation. Animals were killed on day 19 of gestation, 2, 16, 64 h after dosing and blood, maternal tissues, amniotic fluids, placentae, fetal membranes and fetuses were analyzed for radioactivity. No evidence for the transplacental transfer of [14C]Carmoisine or its metabolites was obtained. More than 90% of the radioactivity was excreted in feces and urine within 64 h.

Metabolic fate of food colorants

Evaluation of the chemical and biological data on synthetic and natural food colorants indicates that synthetic colorants in general have been studied more thoroughly than their natural counterparts. The increasing use of natural colorants in processed foods at levels higher than those found in natural sources has raised concern about deficiencies in knowledge, in some cases, of their exact chemical composition, stability, metabolic fate, and toxic potential. Additional studies, particularly of comparative metabolic fate in experimental animals and in man and of genotoxic potential, are required. Until studies with natural colorants comparable to those carried out with synthetic colorants have been completed and evaluated, greater safety of natural colorants cannot be assumed.