Optimization of bacterioruberin production from Halorubrum ruber and assessment of its antioxidant potential.

Haloarchaea produce bacterioruberin, a major C50 carotenoid with antioxidant properties that allow for its potential application in the food, cosmetic, and pharmaceutical industries. This study aimed to optimize culture conditions for total carotenoid, predominantly comprising bacterioruberin, production using Halorubrum ruber MBLA0099. A one-factor-at-a-time and statistically-based experimental design were applied to optimize the culture conditions. Culture in the optimized medium caused an increase in total carotenoid production from 0.496 to 1.966 mg L- 1 Maximal carotenoid productivity was achieved in a 7-L laboratory-scale fermentation and represented a 6.05-fold increase (0.492 mg L-1 d-1). The carotenoid extracts from strain MBLA0099 exhibited a 1.8-10.3-fold higher antioxidant activity in vitro, and allowed for a higher survival rate of Caenorhabditis elegans under oxidative stress conditions. These results demonstrated that Hrr. ruber MBLA0099 has significant potential as a haloarchaon for the commercial production of bacterioruberin.

A Novel Carotenoid-Producing Bacterium, Paenibacillus aurantius sp. nov., Isolated from Korean Marine Environment.

The novel bacterial strain MBLB1776T was isolated from marine mud in Uljin, the Republic of Korea. Cells were Gram-positive, spore-forming, non-motile, and non-flagellated rods. Growth was observed at a temperature range of 10-45 °C, pH range of 6.0-8.0, and NaCl concentrations of 0-4% (w/v). Phylogenetic analysis of the 16S rRNA gene sequence revealed that MBLB1776T belonged to the genus Paenibacillus and was closely related to Paenibacillus cavernae C4-5T (94.83% similarity). Anteiso-C15:0, iso-C16:0, C16:0, and iso-C15:0 were the predominant fatty acids. Menaquinone 7 was identified as the major isoprenoid quinone. The major polar lipids included diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. Its whole genome was 6.3 Mb in size, with a G+C content of 55.8 mol%. Average nucleotide identity and in silico DNA-DNA hybridization values were below the species delineation threshold. Gene function analysis revealed the presence of a complete C30 carotenoid biosynthetic pathway. Intriguingly, MBLB1776T harbored carotenoid pigments, imparting an orange color to whole cells. Based on this comprehensive polyphasic taxonomy, the MBLB1776T strain represents a novel species within the genus Paenibacillus, for which the name Paenibacillus aurantius sp. nov is proposed. The type strain was MBLB1776T (=KCTC 43279T = JCM 34220T). This is the first report of a carotenoid-producing Paenibacillus sp.

Probiotic and antioxidant properties of C30 carotenoid-producing Lactiplantibacillus plantarum isolated from kimchi.

This study focuses on the development of functional probiotics using caroteonid-producing lactic acid bacteria (LAB) with antioxidant properties. Thirty LAB strains were evaluated for their probiotic properties. Carotenoid biosynthesis gene cluster (crtMN operon) was detected using polymer chain reaction (PCR). The carotenoid identified as 4,4'-diaponeurosporene was analyzed via UV visible absorption spectra and HPLC. Five carotenoid-producing strains showed antioxidant activities. Lactiplantibacillus plantarum MGB0112, which showed the highest carotenoid production measuring at 470 nm of absorbance per ml of culture broth (0.014 A470nm/ml), showed low pH (56.5%) and bile salt (97.8%) tolerance with high adhesion properties (55.1% for toluene). Furthermore, this strain and 4,4'-diaponeurosporene extract exhibited antioxidant activity (99.5 and 40.1%, respectively) against DPPH free radicals in vitro. Their antioxidant properties were confirmed in vivo (45.6 and 55.2% survival rates in Caenorhabditis elegans). Therefore, C30 carotenoid-producing strain MGB0112 demonstrates outstanding antioxidant effects and can be a potential functional probiotics.

4,4'-Diaponeurosporene Production as C30 Carotenoid with Antioxidant Activity in Recombinant Escherichia coli.

Carotenoids, a group of isoprenoid pigments, are naturally synthesized by various microorganisms and plants, and are industrially used as ingredients in food, cosmetic, and pharmaceutical product formulations. Although several types of carotenoids and diverse microbial carotenoid producers have been reported, studies on lactic acid bacteria (LAB)-derived carotenoids are relatively insufficient. There is a notable lack of research focusing on C30 carotenoids, the functional characterizations of their biosynthetic genes and their mass production by genetically engineered microorganisms. In this study, the biosynthesis of 4,4'-diaponeurosporene in Escherichia coli harboring the core biosynthetic genes, dehydrosqualene synthase (crtM) and dehydrosqualene desaturase (crtN), from Lactiplantibacillus plantarum subsp. plantarum KCCP11226 was constructed to evaluate and enhance 4,4'-diaponeurosporene production and antioxidant activity. The production of 4,4'-diapophytoene, a substrate of 4,4'-diaponeurosporene, was confirmed in E. coli expressing only the crtM gene. In addition, recombinant E. coli carrying both C30 carotenoid biosynthesis genes (crtM and crtN) was confirmed to biosynthesize 4,4'-diaponeurosporene and exhibited a 6.1-fold increase in carotenoid production compared to the wild type and had a significantly higher antioxidant activity compared to synthetic antioxidant, butylated hydroxytoluene. This study presents the discovery of an important novel E. coli platform in consideration of the industrial applicability of carotenoids.

Antioxidant Potential and Capacity of Microorganism-Sourced C30 Carotenoids-A Review.

Carotenoids are lipophilic tetraterpenoid pigments produced by plants, algae, arthropods, and certain bacteria and fungi. These biologically active compounds are used in the food, feed, and nutraceutical industries for their coloring and the physiological benefits imparted by their antioxidant properties. The current global carotenoid market is dominated by synthetic carotenoids; however, the rising consumer demand for natural products has led to increasing research and development in the mass production of carotenoids from alternative natural sources, including microbial synthesis and plant extraction, which holds a significant market share. To date, microbial research has focused on C40 carotenoids, but studies have shown that C30 carotenoids contain similar-and in some microbial strains, greater-antioxidant activity in both the physical and chemical quenching of reactive oxygen species. The discovery of carotenoid biosynthetic pathways in different microorganisms and advances in metabolic engineering are driving the discovery of novel C30 carotenoid compounds. This review highlights the C30 carotenoids from microbial sources, showcasing their antioxidant properties and the technologies emerging for their enhanced production. Industrial applications and tactics, as well as biotechnological strategies for their optimized synthesis, are also discussed.

Paenibacillus mellifer sp. nov., isolated from gut of the honey bee Apis mellifera.

An isolate, designated MBLB2552T, was isolated from the gut of the honey bees (Apis mellifera L.) and identified as a member of the genus Paenibacillus based on the sequences of the 16S rRNA gene sequences. The most closely related species to strain MBLB2552T were Paenibacillus timonensis 2301032 T, Paenibacillus barengoltzii NBRC 101215 T, and Paenibacillus macerans IAM 12467 T, with similarity values of 98.1, 97.21 and 97.0%, respectively, based on 16S rRNA gene sequences. The genome size and G + C content of MBLB2552T were 5.2 Mb and 52.4%, respectively. The Ortho average nucleotide identity (OrthoANI) and in silico DNA-DNA hybridization (isDDH) values between strain MBLB2552T and the type strains of the closest species were below the species delineation threshold. Comparative genomic analysis showed that most core POGs of strain MBLB2552T and other related taxa were related to translation, ribosomal structure and biogenesis (J) and carbohydrate metabolism in the COG category and KEGG pathways, respectively. Strain MBLB2552T was Gram stain-positive, spore-forming, rod-shaped, facultative anaerobic, motile, and grew at 20‒45 °C in 0‒2% (w/v) NaCl at pH 6.0‒9.0. The major polar lipids identified were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylserine, unidentified polar lipids, and an unidentified glycolipid. We propose that strain MBLB2552T represents the type strain of the genus Paenibacillus and its name Paenibacillus mellifer sp. nov. is proposed. The type of strain was MBLB2552T (= JCM 35371 T = KCTC 43386 T).

Genomic and physiological analysis of C50 carotenoid-producing novel Halorubrum ruber sp. nov.

A novel haloarchaeal species designated as MBLA0099T was isolated from seawater near Yeongheung Island. Cells were Gram-negative, non-motile, red-pigmented, and rod-shaped. They grew at 10-45°C, within pH 5.5-9.0, and between 7.5% and 30% NaCl concentrations. Cells were able to grow without Mg2+ and were lysed in distilled water. The size of the whole-genome and G + C content of DNA was 3.02 Mb and 68.9 mol%, respectively. Phylogenetic analysis shows that the strain MBLA0099T belongs to the genus Halorubrum. The average nucleotide and amino acid identity, and in silico DNA-DNA hybridization values were below the species delineation threshold. Pan-genomic analysis revealed that 3.2% of all genes present in strain MBLA0099T were unique to the strain. The red carotenoid produced by strain MBLA0099T was subjected to spectrometric and chromatographic analyses and confirmed to be bacterioruberin as C50 carotenoid. Mevalonic acid, terpenoid backbone, and carotenoid biosynthesis pathway were annotated for strain MBLA0099T. The C50 carotenoid production by strain MBLA0099T was also enhanced under various stress conditions including relatively netural pH, high oxidative and salinity conditions. Additionally, the strain MBLA0099T-derived bacterioruberin showed the antioxidant activity with EC50 value of 12.29 µg/ml, based on the evaluation of DPPH free radical scavenging activity. The present study would be the first report on the identification of C50 carotenoid from the strain MBLA0099T representing a novel species of the genus Halorubrum, for which the name Halorubrum ruber sp. nov. is proposed. The typestrain used was MBLA0099T (= KCTC 4296T = JCM 34701T).

Fictibacillus marinisediminis sp. nov., a nitrate-reducing bacterium isolated from marine sediment in Hupo Basin, Republic of Korea.

An isolate, designated strain KIGAM418T was isolated from marine mud below 192 m depth in the Hupo Basin, Republic of Korea. Strain KIGAM418T was Gram-stain positive, spore-forming, rod-shaped, facultatively anaerobic, and grew at 10‒45 °C, in 0‒2% (w/v) NaCl at pH 4.0‒12.0. The strain tested positive for catalase, oxidase, and motility. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain KIGAM418T was related to the genus Fictibacillus. The strain showed the highest similarity to Fictibacillus rigui WPCB074T (98.0-98.1%) and Fictibacillus solisalsi YC1T (97.2-97.8%). The diagnostic diamino acid of the cell wall was meso-diaminopimelic acid. The major fatty acids were characterized as anteiso-C15:0 and iso-C15:0. Strain KIGAM418T possessed diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine as the major polar lipids and menaquinone-7 as the predominant menaquinone. The genome size and G + C content were 4.56 Mb and 43.2 mol%, respectively. According to predicted functional genes of the genome, the category of amino acid transport and metabolism was mainly distributed. Based on the polyphasic taxonomic data, strain KIGAM418T represents a novel species of the genus Fictibacillus, for which the name Fictibacillus marinisediminis sp. nov. is proposed. The type strain is KIGAM418T (= KCTC 43291 T = JCM 34437 T).

Genomic and Physiological Characterization of Metabacillus flavus sp. nov., a Novel Carotenoid-Producing Bacilli Isolated from Korean Marine Mud.

The newly isolated strain KIGAM252T was found to be facultatively anaerobic, Gram-stain-positive, spore-forming, and rod-shaped. They grew at 10-45 °C, pH 6.0-10.0, and were able to tolerate up to 6% NaCl in the growth medium. Phylogenetic analysis indicated that the KIGAM252T strain was related to the genus Metabacillus. The cell membrane fatty acid composition of strain KIGAM252T included C15:0 anteiso and C15:0 iso (25.6%) as the major fatty acids, and menaquinone 7 was the predominant isoprenoid quinone. The major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The size of the whole genome was 4.30 Mbp, and the G + C content of the DNA was 43.8%. Average nucleotide and amino acid identity and in silico DNA-DNA hybridization values were below the species delineation threshold. Pan-genomic analysis revealed that 15.8% of all genes present in strain KIGAM252T was unique to the strain. The analysis of the secondary biosynthetic pathway predicted the carotenoid synthetic gene cluster in the strain KIGAM252T. Based on these current polyphasic taxonomic data, strain KIGAM252T represents a novel species of the genus Metabacillus that produces carotenoids, for which we propose the name Metabacillus flavus sp. nov. The type of strain was KIGAM252T (=KCTC 43261T = JCM 34406T).

Nocardioides luti sp. nov., belonging to the family Nocardioidaceae isolated from kaolinite, exhibiting the biosynthesis potential of alkylresorcinol.

A novel Gram-staining-positive, short rod-shaped, non-motile, and non-pigmented actinobacterial strain (KIGAM211T) was isolated from kaolinite, a soft white clay mineral, collected from Sancheong in the Republic of Korea. On the basis of 16S rRNA gene sequence analysis, strain KIGAM211T was determined to belong to the genus Nocardioides and was most closely related to N. ungokensis UKS-03T (97.5% similarity). Cells could grow between 4 and 35 °C (optimum 30 °C), 0-3% (w/v) NaCl concentration (optimum 0%) and pH 5.5-8.5 (optimum 7.0) on R2A agar. Morphological appearance of colonies was cream-white, arranged singly or in groups. Biochemical characterization of strain KAGAM211T indicated that it could hydrolyze casein, gelatin, Tweens 40 and tyrosine. Furthermore, the strain was positive for both oxidase and catalase activity. Strain KIGAM211T was characterized chemotaxonomically by MK-8 (H4) as the predominant menaquinone and phosphatidylglycerol (PG) and phosphatidylinositol (PI) as the major polar lipids. Major fatty acids were iso-C16:0 and C18:1 ω9c. The Ortholog average nucleotide identity (OrthoANI) and in silico DNA-DNA hybridization (isDDH) values between strain KIGAM211T and its most closely related strains of the Nocardioides genus were < 82% and < 24%, respectively, suggesting that strain KIGAM211T represent a novel species. The whole genome size of KIGAM211T was 4.52 Mb, comprising a total of 4,294 genes with DNA G + C content of 72.3 mol%. The genome of strain KIGAM211T also comprises the biosynthetic gene cluster for alkylresorcinol as secondary metabolite. The results of physiological, taxonomical, phylogenetic, and whole genome analyses allowed for differentiation of strain KIGAM211T from the recognized Nocardioides species. Therefore, strain KIGAM211T is considered to represent a novel species, for which the name Nocardioides luti sp. nov. (type strain KIGAM211T = KCTC 49364T = JCM 33859T) is proposed.

Halobellus ruber sp. nov., a deep red-pigmented extremely halophilic archaeon isolated from a Korean solar saltern.

A novel halophilic archaeon, strain MBLA0160T, was isolated from a solar saltern in Sorae, Republic of Korea. The cells are deep-red pigmented, Gram-negative, rod shaped, motile, and lysed in distilled water. The strain MBLA0160T grew at 25-45 °C (optimum 37 °C), in 15-30% (w/v) NaCl (optimum 20%) and 0.1-1.0 M MgCl2 (optimum 0.3-0.5 M) at pH 5.0-9.0 (optimum 7.0). Phylogenetic analysis based on the 16S rRNA sequence showed that this strain was related to two species within the genus Halobellus (Hbs.), with 98.4% and 95.8% similarity to Hbs. salinus CSW2.24.4 T and Hbs. clavatus TNN18T, respectively. The major polar lipids of the strain MBLA160T were phosphatidylglycerol, phosphatidylglycerol sulfate, and phosphatidylglycerol phosphate methyl ester. The genome size, G + C content, and N50 value of MBLA0160T were 3.49 Mb, 66.5 mol%, and 620,127 bp, respectively. According to predicted functional proteins of strain MBLA0160T, the highest category was amino acid transport and metabolism. Genome rapid annotation showed that amino acid and derivatives was the most subsystem feature counts. Pan-genomic analysis showed that strain MBLA0160T had 97 annotated unique KEGG, which were mainly included metabolism and environmental information processing. Ortholog average nucleotide identities (OrthoANI) and in silico DNA-DNA hybridization (isDDH) values between the strain MBLA0160T and other strains of the genus Halobellus were under 84,4% and 28.1%, respectively. The genome of strain MBLA0160T also contain the biosynthetic gene cluster for C50 carotenoid as secondary metabolite. Based on the phylogenetic, phenotypic, chemotaxonomic properties, and comparative genomic analyses, strain MBLA0160T is considered to represent a novel species of the genus Halobellus, for which the name Halobellus ruber sp. nov. is proposed. The type strain is MBLA0160T (= KCTC 4291 T = JCM 34172 T).

Crafting a 1.5 µm pixel pitch spatial light modulator using Ge2Sb2Te5 phase change material [Invited].

For this research, we have developed key technologies for a 1.5 µm pixel pitch spatial light modulator (SLM) using Ge2Sb2Te5 (GST) phase change material. To uniformly modulate each pixel, we designed a lateral pixel structure in which a heating current flows through a bottom indium tin oxide layer. To check hologram reconstruction both after multilevel fabrication processes and before implementing full source and driver circuits, we fabricated an 8K×2K hologram on the topology by changing the GST film's phase using laser irradiation. To overcome the limitation of SLM size, we tested a physical tiling structure and found that flatness of tiled SLMs was the most important factor in the realization of holographic displays.

Correction: Rewritable full-color computer-generated holograms based on color-selective diffractive optical components including phase-change materials.

Correction for 'Rewritable full-color computer-generated holograms based on color-selective diffractive optical components including phase-change materials' by Chi-Young Hwang et al., Nanoscale, 2018, DOI: 10.1039/c8nr04471f.

Rewritable full-color computer-generated holograms based on color-selective diffractive optical components including phase-change materials.

We propose rewritable full-color computer-generated holograms (CGHs) based on color-selective diffraction using the diffractive optical component with the resonant characteristic. The structure includes an ultrathin layer of phase-change material Ge2Sb2Te5 (GST) on which a spatial binary pattern of amorphous and crystalline states can be recorded. The CGH patterns can be easily erased and rewritten by the pulsed ultraviolet laser writing technique owing to the thermally reconfigurable characteristic of GST. We experimentally demonstrate that the fabricated CGH, having a fine pixel pitch of 2 µm and a size of 32.8 × 32.8 mm2, reconstructs the three-dimensional holographic images. In addition, the feasibility of the rewritable property is verified by erasing and rewriting part of the CGH.

Nitrogen Doping Effect for Improving Operation Reliability of Phase Modulator Using Ge2Sb2Te5 Thin Film for Hologram Image Implementation.

A phase modulation device was proposed for the implementation of hologram image for display applications. A Ge2Sb2Te5 (GST) film as thin as 7 nm was prepared between the ITO films to form the cavities corresponding a unit pixel. Nitrogen was incorporated into the GST for improving the thermal stability of the GST active region. The effects of the nitrogen doping on the physical properties of GST was investigated with the variations in doping amounts. The nitrogen incorporation was found to reduce the surface micro-roughness and to improve the thermal stability of the GST even after the crystallization by effectively suppressing the excessive grain growth. As results, the number of repeatable operations for the fabricated phase modulation device was evidently improved from 10 to 69 cycles when a 2.7-at% nitrogen was doped into the GST.

Gas molecule sensing of van der Waals tunnel field effect transistors.

van der Waals (vdW) heterostructures with two-dimensional (2D) crystals such as graphene, hexagonal boron nitride (hBN) and transition metal dichalcogenides (TMDCs) allow us to demonstrate atomically thin field-effect transistors (FETs), photodetectors (PDs) and photovoltaic devices capable of higher performance and greater stability levels than conventional devices. Although there have been studies of gas molecule sensing with 2D crystal channels, vdW heterostructures based on 2D crystals have not been employed thus far. Here, utilizing graphene/WS2/graphene (G/WS2/G) vdW heterostructure tunnel FETs, we demonstrate the rectification behavior of the sensitivity signal by tuning the WS2 potential barriers as a function of the gas molecule concentration and devise a fingerprint map of the sensitivity variation corresponding to an individual ratio of two different molecules in a gas mixture. Because the separation of different gas molecule concentrations from gas mixtures is in high demand in the gas-sensing research field, this result will greatly assist in the progress on selective gas sensing.

Holographic image generation with a thin-film resonance caused by chalcogenide phase-change material.

The development of digital holography is anticipated for the viewing of 3D images by reconstructing both the amplitude and phase information of the object. Compared to analog holograms written by a laser interference, digital hologram technology has the potential to realize a moving 3D image using a spatial light modulator. However, to ensure a high-resolution 3D image with a large viewing angle, the hologram panel requires a near-wavelength scale pixel pitch with a sufficient large numbers of pixels. In this manuscript, we demonstrate a digital hologram panel based on a chalcogenide phase-change material (PCM) which has a pixel pitch of 1 µm and a panel size of 1.6 × 1.6 cm2. A thin film of PCM encapsulated by dielectric layers can be used for the hologram panel by means of excimer laser lithography. By tuning the thicknesses of upper and lower dielectric layers, a color-selective diffraction panel is demonstrated since a thin film resonance caused by dielectric can affect to the absorption and diffraction spectrum of the proposed hologram panel. We also show reflection color of a small active region (1 µm × 4 µm) made by ultra-thin PCM layer can be electrically changed.

Reflection-type spatial amplitude modulation of visible light based on a sub-wavelength plasmonic absorber.

We present a method for reflection-type spatial amplitude modulation using a sub-wavelength plasmonic absorber structure that can operate in the visible region. We utilize a pixelated array of absorbing elements based on a two-dimensional sub-wavelength metal grating, and the reflectance of each pixel is controlled by simple structural modification. For the purpose of validation, numerical simulations were performed on an amplitude modulation hologram fabricated using our method.

Fast focus estimation using frequency analysis in digital holography.

A novel fast frequency-based method to estimate the focus distance of digital hologram for a single object is proposed. The focus distance is computed by analyzing the distribution of intersections of smoothed-rays. The smoothed-rays are determined by the directions of energy flow which are computed from local spatial frequency spectrum based on the windowed Fourier transform. So our method uses only the intrinsic frequency information of the optical field on the hologram and therefore does not require any sequential numerical reconstructions and focus detection techniques of conventional photography, both of which are the essential parts in previous methods. To show the effectiveness of our method, numerical results and analysis are presented as well.

Anamorphic optical transformation of an amplitude spatial light modulator to a complex spatial light modulator with square pixels [invited].

A method is proposed for the construction of a square pixel complex spatial light modulator (SLM) from a commercial oblong full-high-definition (full-HD) amplitude SLM using an anamorphic optical filter. In the proposed scheme, one half-band of the optical Fourier transform of the amplitude-only spatial light field is rejected in the optical Fourier plane and the other half-band is reformatted to be an effective complex SLM with square pixels. This has an advantage in the viewing window plane since the shape of the viewing window becomes square and more ideal for observers who watch the hologram contents through it. For optimal transformation, the amplitude computer generated hologram encoding scheme was developed. Mathematical modeling of the proposed system is described herein, and it was experimentally demonstrated that the effective complex SLM displays complex holographic three-dimensional images with a clear depth discrimination effect.