Blue Color Formation Research Articles

Hexagonal Boron Nitride Quantum Dots Embedded on Layer-by-Layer Films for Peroxidase-Assisted Colorimetric Detection of β-Galactosidase Producing Pathogens.

Pathogen detection has become a major research area all over the world for water quality surveillance and microbial risk assessment. Therefore, designing simple and sensitive detection kits plays a key role in envisaging and evaluating the risk of disease outbreaks and providing quality healthcare settings. Herein, we have designed a facile and low-cost colorimetric sensing strategy for the selective and sensitive determination of β-galactosidase producing pathogens. The hexagonal boron nitride quantum dots (h-BN QDs) were established as a nanozyme that showed prominent peroxidase-like activity, which catalyzes 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H2O2. The h-BN QDs were embedded on a layer-by-layer assembled agarose biopolymer. The β-galactosidase enzyme partially degrades β-1,4 glycosidic bonds of agarose polymer, resulting in accessibility of h-BN QDs on the solid surface. This assay can be conveniently conducted and analyzed by monitoring the blue color formation due to TMB oxidation within 30 min. The nanocomposite was stable for more than 90 days and was showing TMB oxidation after incubating it with Escherichia coli (E. coli). The limit of detection was calculated to be 1.8 × 106 and 1.5 × 106 CFU/mL for E. coli and Klebsiella pneumonia (K. pneumonia), respectively. Furthermore, this novel sensing approach is an attractive platform that was successfully applied to detect E. coli in spiked water samples and other food products with good accuracy, indicating its practical applicability for the detection of pathogens in real samples.

Identification and Verification of the Blue Pigment in the Edible Jellyfish (Rhopilema esculentum)

Rhopilema esculentum is widely cultured in Chinese coastal regions and has thousand years of consumption history in China. Despite R. esculentum owns multiple colors (mainly ochre and blue) in aquaculture ponds, little is known about the pigments and color formation. This study identified and verified the blue pigment of R. esculentum. Results showed that the blue pigment of R. esculentum has 262 amino acids with 54.96% identity to the blue pigment protein precursor of Rhizostoma pulmo. The blue pigment of R. esculentum has Kringle and Frizzled domains, which is in accordance with rhizostomins characteristics. Compared to ochre R. esculentum, the expression level of blue pigment increased 3.49-fold in blue R. esculentum. In addition, overexpression of the blue pigment in Rhodosporidium toruloides made transformant cells blue under blue light excitation. Our findings provide knowledge for the blue color formation of R. esculentum and will benefit the color selection of R. esculentum with excellent traits.

Exploring the molecular mechanism of coloration differences in two Meconopsis wilsonii subspecies: australis and orientalis

Flower color diversity is a key taxonomic trait in Meconopsis species, enhancing their appeal as ornamental flowers. However, knowledge of the molecular mechanisms of flower color formation in Meconopsis species is still limited. M. wilsonii subsp. australis (Australis) and M. wilsonii subsp. orientalis (Orientalis) have a developmental stage presenting red-purple flowers, while Orientalis also presents blue coloration at the full-bloom period, making them an important model for exploring the mechanism of blue flower formation in M. wilsonii. In this study, we collected petals from Australis and Orientalis at different developmental stages to compare the coloration differences between the two species and detect the molecular mechanisms of blue color in Orientalis. We identified that cyanidin was the main anthocyanin in the flowers of both species, and the blue color in Orientalis primarily arises from anthocyanins (Cyanidin-3-O-sambubioside). RNA sequencing analysis was performed to detect the gene expression in the anthocyanin biosynthesis pathway, and the results suggested that gene regulation for anthocyanin biosynthesis may not be the direct reason for blue color formation in Orientalis. In addition, the growth solid of Orientalis was rich in Fe and Mg ions, and a large amount of Fe and Mg ions accumulated in the petals of Orientalis. Combined with the gene functional enrichment results, we found that the purple and red-purple colors of these two species were presented by different glycosylation levels of cyanidin, while the violet color of Orientalis might be the results of metalloanthocyanins by Fe and Mg ions, which also relieved the toxicity caused by the high content of Fe and Mg ions in its cells. The environmental adaptation-related genes were highly expressed of in both species, such as adaptation to desiccation, water deprivation, freezing, etc. Our results revealed the coloration differences between Australis and Orientalis and described the molecular mechanisms of blue coloration in Orientalis. The data in our analysis could enrich the genetic resources for M. wilsonii for further studies.

On the Origin of the Blue Color in The Iodine/Iodide/Starch Supramolecular Complex.

The nature of the blue color in the iodine-starch reaction is still a matter of debate. Some textbooks still invoke charge-transfer bands within a chain of neutral I2 molecules inside the hydrophobic channel defined by the interior of the amylose helical structure. However, the consensus is that the interior of the helix is not altogether hydrophobic-and that a mixture of I2 molecules and iodide anions reside there and are responsible for the intense charge-transfer bands that yield the blue color of the "iodine-starch complex". Indeed, iodide is a prerequisite of the reaction. However, some debate still exists regarding the nature of the iodine-iodine units inside the amylose helix. Species such as I3-, I5-, I7- etc. have been invoked. Here, we report UV-vis titration data and computational simulations using density functional theory (DFT) for the iodine/iodide chains as well as semiempirical (AM1, PM3) calculations of the amylose-iodine/iodide complexes, that (1) confirm that iodide is a pre-requisite for blue color formation in the iodine-starch system, (2) propose the nature of the complex to involve alternating sets of I2 and Ix- units, and (3) identify the nature of the charge-transfer bands as involving transfer from the Ix- σ* orbitals (HOMO) to I2 σ* LUMO orbitals. The best candidate for the "blue complex", based on DFT geometry optimizations and TD-DFT spectral simulations, is an I2-I5-I2 unit, which is expected to occur in a repetitive manner inside the amylose helix.

Study of the reaction between genipin and amino acids, dairy proteins, and milk to form a blue colorant ingredient

Currently, one of the biggest challenges of the colorant industry is to obtain natural blue colorants. Among the different options, a blue pigment can be formed by a crosslinking reaction between genipin and primary amine groups. However, at the industrial level, obtaining an ingredient from pure compounds, such as amino acids, is economically unfeasible. The present work aimed to study the reaction and kinetics of the blue color formation, starting the study with pure compounds (genipin and amino acids) to more complex and cheaper natural sources, such as Genipa americana L. fruits and milk. The reaction kinetics of the monomers/dimers for different amino acids reacting with genipin was evaluated, as well as the preferential amino acid, genipin:amino acid ratio and pH, to obtain the most rapid and intense blue color. Finally, the blue pigment formed using milk and its proteins was characterized by SDS-PAGE. The results suggest that the reaction kinetic is influenced by the type and concentration of the amino acid used and the pH of the medium, which could facilitate the further standardization of the industrial process. We also suggested milk as an excellent reaction medium to obtain the colorant from genipin as it presents an ideal pH and favorable amino acid composition to facilitate the reaction.

Chitosan nanoparticles as a new technique in gene transformation into different plants tissues

The utilization of chitosan nanoparticles is a novel technique for gene transformation into plant tissues. It takes a few minutes to transform gene to plant. UidA gene was detected in <i>Escherichia coli</i> (K12 strain) using polymerase chain reaction analysis by UidA-specific primers. The gene was transformed into the explants of two different plant species (<i>Solanum tuberosum</i> and <i>Paulownia tomentosa</i>). These plants have different natures as crop and woody plants respectively. Therefore, they have different abilities to express the UidA gene. The gene is expressed into blue color in plant tissues due to the formation and expression of the GUS enzyme. The transformation of the UidA gene was detected morphologically by the formation of blue color; and molecular using PCR. Chitosan nanoparticles were characterized by UV/Visible spectroscope and photographing with a transmission electron microscope (TEM). As a result of this research, it is suggested that chitosan nanoparticles be used in gene transformation into plant tissues. Because it is safe, quick, and inexpensive, as well as biocompatible and biodegradable.

Impact of thermosonication pretreatment on the production of plant protein-based natural blue colorants

The increase in the consumption of natural and non-dairy products has boosted the worldwide food colorant industry. Thus, the use of non-animal protein sources to produce natural blue compounds from the cross-linking between primary amines and genipin extracted from unripe Genipa americana L. pulp was evaluated in this study. Plant extracts obtained from white rice, oat, peanut, and almond were examined as amine suppliers, extraction media, and carrier systems for the blue compounds. The four plant extracts were thermosonicated at 70 °C and 400 W for 3 min and then subjected to ultrasound-assisted extraction of genipin from unripe genipap pulp at 300 W for 6 min. Thus, this study aimed to evaluate the effects of thermosonication pretreatment and plant material on natural blue colorant production. Four new blue plant-based colorants were produced. Protein availability was the most significant limiting factor in the blue color formation reaction. The acoustic cavitation associated with moderate heat treatment during the thermosonication promoted the rupture of fat globules and starch gelatinization. Furthermore, thermosonication pretreatment showed promising to improve the kinetic stability of the natural blue colorants.

Assessment of violet-blue color formation in Phalaenopsis orchids

BackgroundPhalaenopsis represents an important cash crop worldwide. Abundant flower colors observed in Phalaenopsis orchids range from red-purple, purple, purple-violet, violet, and violet-blue. However, violet-blue orchids are less bred than are those of other colors. Anthocyanin, vacuolar pH and metal ions are three major factors influencing flower color. This study aimed to identify the factors causing the violet-blue color in Phalaenopsis flowers and to analyze whether delphinidin accumulation and blue pigmentation formation can be achieved by transient overexpression of heterologous F3’5’H in Phalaenopsis.ResultsCyanidin-based anthocyanin was highly accumulated in Phalaenopsis flowers with red-purple, purple, purple-violet, and violet to violet-blue color, but no true-blue color and no delphinidin was detected. Concomitantly, the expression of PeF3’H (Phalaenopsis equestrsis) was high, but that of PhF3’5’H (Phalaenopsis hybrid) was low or absent in various-colored Phalaenopsis flowers. Transient overexpression of DgF3’5’H (Delphinium grandiflorum) and PeMYB2 in a white Phalaenopsis cultivar resulted a 53.6% delphinidin accumulation and a novel blue color formation. In contrast, transient overexpression of both PhF3’5’H and PeMYB2 did not lead to delphinidin accumulation. Sequence analysis showed that the substrate recognition site 6 (SRS6) of PhF3’5’H was consistently different from DgF3’5’Hs at positions 5, 8 and 10. Prediction of molecular docking of the substrates showed a contrary binding direction of aromatic rings (B-ring) with the SRS6 domain of DgF3’5’H and PhF3’5’H. In addition, the pH values of violet-blue and purple Phalaenopsis flowers ranged from 5.33 to 5.54 and 4.77 to 5.04, respectively. Furthermore, the molar ratio of metal ions (including Al3+, Ca2+ and Fe3+) to anthocyanin in violet-blue color Phalaenopsis was 190-, 49-, and 51-fold higher, respectively, than those in purple-color Phalaenopsis.ConclusionCyanidin-based anthocyanin was detected in violet-blue color Phalaenopsis and was concomitant with a high pH value and high molar ratio of Al3+, Ca2+ and Fe3+ to anthocyanin content. Enhanced expression of delphinidin is needed to produce true-blue Phalaenopsis.

Theoretical Modeling of Electronic Structures of Polyiodide Species Included in α-Cyclodextrin.

The molecular mechanism of blue color formation in an iodine-starch reaction is studied by employing the iodine-α-cyclodextrin (α-CD) complex as a practical model system that resembles the structural properties of the blue amylose-iodine complex. To this end, we construct, using the quantum chemistry method, a molecular model of the complex (I5-/Li+/2α-CD) that consists of one I5-, two molecules of α-CD, and a lithium cation, and this model is employed as a basic unit in constructing the structural models of polyiodide ions (I5-)n. The initial structure in the geometry optimization is adopted from the α-CD-iodine complex structure obtained from the X-ray crystallography study. The structural models of (I5-)n are built by adding the basic unit n times along the crystal axis and by optimizing the structure using quantum mechanics/molecular mechanics (QM (iodine)/MM (α-CD)) calculations. The electronic absorption spectra of the resulting model structures are calculated by time-dependent density functional theory (TD-DFT). We find that I5- acts as a basic unit of coloration in the visible region. The visible color originates from the electronic transition within the I5- molecule, and any charge transfer between the I5- ion and either of α-CD or a coexisting counter cation is not involved. We also reveal that the electronic transitions of (I5-)n are delocalized, which accounts for the well-known observation that the color of the iodine-starch reaction becomes bluish with an increase in the chain length of amylose. Furthermore, the preresonance Raman spectra calculated from the model suggest that the vibrational motions are localized in the I5- subunit dominantly. A comparison between an experimental absorption spectrum feature of the α-CD-iodine complex and the calculated ones of (I5-)n ions with various n values suggests that (I5-)4 polyiodide ions tend to be populated dominantly in the α-CD-iodine complex under aqueous conditions.

Milk colloidal system as a reaction medium and carrier for the natural blue colorant obtained from the cross-linking between genipin and milk proteins

A promising natural blue colorant was obtained from the cross-linking between genipin and milk proteins. Milk was simultaneously used to extract genipin from the unripe genipap (Genipa americana L.) and evaluated as a reaction medium and carrier for the novel blue colorant. The effects of the milk composition (skimmed, semi-skimmed, and whole) on the kinetic of blue color formation in the colorant-loaded milk samples during their cold storage time for 96 h were evaluated using their color parameters and free-genipin content. The reaction between milk proteins and genipin were evaluated by FTIR spectroscopy. In addition, the blue colorant-loaded milk samples were characterized according to their droplet size distribution, microstructure, and phase separation kinetics. The milk fat content influenced the genipin recovery while the milk with higher protein content contributed to obtaining a more intense blue color. Using whole milk with 3.0 g/100 g fat content favored the light scattering and, thus, a blue colorant with a more intense −b∗ and L∗ values was obtained. On the other hand, the use of skimmed milk with 0.5 g/100 g fat content resulted in more consumption of genipin due to its more protein content for the reaction of blue color compounds formation. Thus, a more intense and darker blue coloration was observed with lower light scattering. The milk composition did not modify the phase separation kinetics of the blue colorant-loaded milk. Therefore, our results have demonstrated that the milk was a suitable medium for the reaction of blue color formation and also a good blue compounds carrier. Industrial relevanceConsumer demands for natural colorants have increased in the last years.Thus, the new food industry challenge is to develop novel healthy, safe and high-quality food products based on natural colorants. Currently, the colorant market does not have still available a natural blue colorant. Therefore, the development of a novel natural blue colorant from plant material could meet this worldwide demand increasing the added value of many products such as ice cream, dairy beverages, and candies.

Low-frequency and high-power ultrasound-assisted production of natural blue colorant from the milk and unripe Genipa americana L.

This study presents the production of a novel natural blue colorant obtained from the cross-linking between milk proteins and genipin assisted by low-frequency and high-power ultrasound technology. Genipin was extracted from unripe Genipa americana L. using milk as a solvent. Also, milk colloidal system was used as a reaction medium and carrier for the blue color compounds. The effects of ultrasound nominal power (100, 200, 300, and 400W) on the blue color formation kinetics in milk samples were evaluated at 2, 24, and 48h of cold storage in relation to their free-genipin content and color parameters. In addition, Fourier transform infrared (FTIR) spectrum, droplet size distribution, microstructure, and kinetic stability of the blue colorant-loaded milk samples were assessed. Our results have demonstrated that the ultrasound technology was a promising and efficient technique to obtain blue colorant-loaded milk samples. One-step acoustic cavitation assisted the genipin extraction and its diffusion into the milk colloidal system favoring its cross-linking with milk proteins. Ultrasound process intensification by increasing the nominal power promoted higher genipin recovery resulting in bluer milk samples. However, the application of high temperatures associated with intensified acoustic cavitation processing favored the occurrence of non-enzymatic browning due to the formation of complex melanin substances from the Maillard reaction. Also, the blue milk samples were chemically stable since their functional groups were not modified after ultrasound processing. Likewise, all blue colorant-loaded milk samples were kinetically stable during their cold storage. Therefore, a novel natural blue colorant with high-potential application in food products like ice creams, dairy beverages, bakery products, and candies was produced.

A new thin-layer chromatography–direct bioautography assay for the qualitative and quantitative determination of peroxidase inhibitors in plant extracts

Thin-layer chromatography (TLC) hyphenated to bioassays is a modern tool used for discovery of drugs with diverse biological activities from plant extracts which justifies the continuous need for developing such methods. A new TLC–bioautography assay for detecting peroxidase enzyme inhibitors was developed and validated in this study. Peroxidases are related to pathogenesis of many diseases such as neurodegenerative disorders and rheumatoid arthritis and are considered as inflammatory markers. The developed TLC–bioautography method was based on reaction of peroxidase with hydrogen peroxide and the subsequent formation of blue color by the reaction between the released oxygen and benzidine. Compounds with peroxidase inhibition activity are observed as yellowish spots against a blue background. The developed method was validated according to the ICH guidelines. Quantitative estimation of peroxidase inhibitors was achieved by applying image analyses techniques, showing good linearity (R2 = 0.998), accuracy (% recovery 96.6–99.7%), intra-day precisions (RSD% = 0.95–2.35) and inter-day precision (RSD% = 1.80–3.20) as well as low LOD (0.28 μg/spot) and LOQ (0.85 μg/spot). The developed method was applied to different Juniperus species fractions as a demonstrative illustration. Overall, the method proved to be efficient, simple and rapid for identification of peroxidase inhibitors in complex matrices and can be applied in high-throughput screening of plant extracts.

Elucidating the Genotoxicity of Synthetic Food Preservatives with the SOS Chromotest

The increased use of synthetic food preservatives makes it imperative to screen for their potential health risks. This project aimed to delineate the genotoxic potential and effects of commonly used synthetic food preservatives, specifically sodium nitrite, potassium sulfate, and hydrogen peroxide. We employed a colorimetric assay designed to test the induction of the DNA damage response using beta-galactosidase (β-gal) as a reporter. Evidence suggests these food preservatives may be genotoxic due to their ability to impair normal cellular pathways. We hypothesized that sodium nitrite would be the most genotoxic because nitrites are precursors to N-nitrosamines, a class of compounds that are carcinogenic byproducts of metabolism. Potassium sulfate and hydrogen peroxide were also initially hypothesized to be genotoxic. Two-fold serial dilutions were performed, and blue color formation was analyzed qualitatively and quantitatively to assess genotoxicity levels. The hypotheses were partially supported as all synthetic food preservatives demonstrated some degree of genotoxicity before and after metabolic activation; potassium sulfate was shown to be the most genotoxic. The inclusion of mammalian hepatic enzymes permitted for better correlation to humans, as results provided insight on the genotoxicity of food preservatives after normal metabolic function. These findings can inform future toxicology research to potentially prevent genetic damage and carcinogenesis.

Preparation of topographically remarkable cobalt microspheres for colorimetric detection of dopamine and elucidation of its sensing mechanism

In this work, a new colorimetric probe is prepared and demonstrated for the detection of dopamine (DA), an important neurotransmitter. The proposed colorimetric probe is prepared using bovine serum albumin (BSA) modified cobalt hydroxide microspheres (CoMSPs@BSA) and subsequently explored for the selective colorimetric detection of DA. The sensing studies are monitored using UV–visible absorbance spectroscopy. Interestingly upon addition of DA, an intense blue color is formed suggesting the potential use of this probe for naked eye detection of DA. The mechanism behind the sensing is investigated using time dependent UV–visible absorbance spectroscopic study and cyclic voltammetry. These studies clearly indicate the ligand exchange reaction is responsible for the resultant blue color formation. Further using this colorimetric probe a concentration range from 5.3 to 211 µM DA could easily be detected. Limit of detection of this DA sensor is found to be 5 × 10−6 M. Similarly a linear relation is observed from the calibration graph plotted between the concentration and absorption intensity corresponding to ligand exchange of BSA by DA. Moreover, this sensing probe (CoMSPs@BSA) is found to be highly selective among a wide range of other commonly interfering biomolecules. Topographically remarkable cobalt microspheres are prepared using a simple method and explored for the colorimetric detection of dopamine. The sensing mechanism is elucidated using UV–visible spectroscopic and electrochemical studies.

Screening of Amylase and Cellulase Enzymes from Marine Actinomycetes

Actinomycetes have an important role in the Industrial enzymes, Antibiotics, vitamins and organic acids. We have isolated 114 actinomycetes strains from Chennai coastal region by using starch casein agar plate method. Out of these 114 actinomycetes strains, 13 actinomycetes strains showed amylase activity by starch agar plate method and 12 strains showed cellulase activity by cellulase agar plate method, which was indicated by clear zone of dark blue color formation for amylase activity and dark yellow color formation for cellulase activity. Based on the maximum amylase and cellulase producing strains MB23 and BN08 was found to be a potential strains for further investigation.

Developing Paper Based Diagnostic Technique to Detect Uric Acid in Urine.

Urinary or serum uric acid concentration is an indicator of chronic kidney condition. An increase in uric acid concentration may indicate renal dysfunction. Reliable instantaneous detection of uric acid without requiring sophisticated laboratory and analytical instrumentation, such as: chromatographic and spectrophotometric methods, would be invaluable for patients with renal complication. This paper reports the early development of a simple, low-cost, instantaneous and user-friendly paper based diagnostic device (PAD) for the qualitative and quantitative detection of uric acid in urine. A colorimetric detection technique was developed based on the intensity of Prussian blue color formation on paper in presence of uric acid; the reaction rate of corresponding chemical reactions on paper surface was also studied. Based on the colorimetric signal produced on paper surface, a calibration curve was developed to detect unknown concentration of uric acid in urine. The effect of temperature on formation of color signal on paper surface was also analyzed. In this study, estimation of urinary uric acid using MATLAB coding on a windows platform was demonstrated as the use of software application and digital diagnostics. This paper-based technique is faster and less expensive compared to traditional detection techniques. The paper-based diagnostic can be integrated with a camera of smart phone, tablet computer or laptop and an image processing application (using windows/android/IOS platform) as a part of digital diagnostics. Therefore, with proper calibration, the paper-based technique can be compatible and economical to the sophisticated detection techniques used to detect urinary uric acid.

Densification of cyanobacteria from a lake leading to production of β‐cyclocitral and related volatile organic compounds and species change

SUMMARYThe purpose of the present study was to demonstrate that the lysis with the blue color formation was caused by densification of the cyanobacteria, and related events of the species change in the cyanobacteria were induced by the resulting volatile organic compounds (VOCs), particularly β‐cyclocitral. In order to obtain a high cell density of cyanobacteria in the laboratory, a concentration technique (graduated cylinder method) using the buoyancy of the gas vesicles was successfully used. The collected scum contained mainly Dolichospermum spp. and Microcystis, and the dispersed cyanobacteria were concentrated in the surface layer after several hours and the concentration ratio became approximately 10. The concentrated cyanobacteria were gradually lysed, while some of the cyanobacteria sank to the bottom, which finally died and disappeared. This method has the additional advantage that it is possible to visualize the entire lysis process. During the concentration process, β‐cyclocitral and its oxidation products together with β‐ionone were significantly detected. Because β‐cyclocitral was easily oxidized to the corresponding carboxylic acid, the pH of the water in the graduated cylinder decreased to approximately 6. Under favorable conditions, lysis with the blue color from phycocyanin could be observed due to the acid stress. Overall, the results of the present study were consistent with the hypothesis that VOCs were produced when the cyanobacteria are highly dense, and that the lysis with the blue color formation occurs due to the higher density.

Transcriptome sequencing and metabolite analysis for revealing the blue flower formation in waterlily.

BackgroundWaterlily (Nymphaea spp.), a perennial herbaceous aquatic plant, is divided into two ecological groups: hardy waterlily and tropical waterlily. Although the hardy waterlily has no attractive blue flower cultivar, its adaptability is stronger than tropical waterlily because it can survive a cold winter. Thus, breeding hardy waterlily with real blue flowers has become an important target for breeders. Molecular breeding may be a useful way. However, molecular studies on waterlily are limited due to the lack of sequence data.ResultsIn this study, six cDNA libraries generated from the petals of two different coloring stages of blue tropical waterlily cultivar Nymphaea ‘King of Siam’ were sequenced using the Illumina HiSeq™ 2500 platform. Each library produced no less than 5.65 Gb clean reads. Subsequently, de novo assembly generated 112,485 unigenes, including 26,206 unigenes annotated to seven public protein databases. Then, 127 unigenes could be identified as putative homologues of color-related genes in other species, including 28 up-regulated and 5 down-regulated unigenes. In petals, 16 flavonoids (4 anthocyanins and 12 flavonols) were detected in different contents during the color development due to the different expression levels of color-related genes, and four flavonols were detected in waterlily for the first time. Furthermore, UA3GTs were selected as the most important candidates involved in the flavonoid metabolic pathway, UA3GTs induced blue petal color formation in Nymphaea ‘King of Siam’.ConclusionsThis study will improve our understanding of the molecular mechanism of blue flowers in waterlily and provide the basis for molecular breeding of blue hardy waterlily cultivars.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3226-9) contains supplementary material, which is available to authorized users.

Characteristic oxidation behavior of β-cyclocitral from the cyanobacterium Microcystis.

The cyanobacterium Microcystis produces volatile organic compounds such as β-cyclocitral and 3-methyl-1-butanol. The lysis of cyanobacteria involving the blue color formation has been occasionally observed in a natural environment. In this study, we focused on the oxidation behavior of β-cyclocitral that contributed to the blue color formation in a natural environment and compared β-cyclocitral with a structurally related compound concerning its oxidation, acidification, and lytic behavior. The oxidation products of β-cyclocitral were identified by the addition of β-cyclocitral in water, in which 2,2,6-trimethylcyclohex-1-ene-1-yl formate and 2,2,6-trimethylcyclohexanone were structurally characterized. That is, β-cyclocitral was easily oxidized to produce the corresponding carboxylic acid and the enol ester in water without an oxidizing reagent, suggesting that this oxidation proceeded according to the Baeyer-Villiger oxidation. The oxidation behavior of β-cyclocitral in a laboratory was different from that in the natural environment, in which 2,2,6- trimethylcyclohexanone was detected at the highest amount in the natural environment, whereas the highest amount in the laboratory was β-cyclocitric acid. A comparison of β-cyclocitral with structurally similar aldehydes concerning the lytic behavior of a Microcystis strain and the acidification process indicated that only β-cyclocitral was easily oxidized. Furthermore, it was found that a blue color formation occurred between pH 5.5 and 6.5, suggesting that chlorophyll a and β-carotene are unstable and decomposed, whereas phycocyanin was stable to some extent in this range. The obtained results of the characteristic oxidation behavior of β-cyclocitral would contribute to a better understanding of the cyanobacterial life cycle.

Bioelectrogenesis Detection of Inoculums Using Electrochromic Tungsten Oxide and Performance Evaluation in Microbial Fuel Cells

Rapid detection of bio-electrogenesis in the anodic inoculum is the bottleneck in start-up of microbial fuel cells (MFCs). Use of hydrothermally synthesized electrochromic WO3 fibers is proposed for detecting electrogenic activity of inoculum collected from different sources, such as anaerobic septic tank sludge, wet garden soil, cow dung, and decomposed lignocellulosic waste. Bio-electrochemical reactions between WO3 and inoculum sample in test tube confirms better electron transfer activity of anaerobic septic tank sludge and cow dung as an inoculum through formation of dark blue color. Four dual chambered MFCs were inoculated with septic tank sludge (MFC-1), wet garden soil (MFC-2), cow dung slurry (MFC-3), and with anaerobically decomposed lignocellulosic waste (MFC-4). Maximum power densities of 15.58, 5.10, 11.44, and 1.18 mW/m2 were obtained in MFC-1, MFC-2, MFC-3 and MFC-4, respectively; confirming septic tank sludge and cow dung slurry as better inoculum sources. This simple approach of rapid switching of hexagonal WO3 to blue coloration in presence of electrogenic bacteria is useful to establish correlation between activities of electrogens in the inoculums, and detection of electrogenic activity of selected inoculum within half an hour, to expedite start-up of MFCs by selecting appropriate inoculum.