Bacteroides faecium sp. nov. isolated from human faeces.

A novel bacterial strain, CBA7301T, was isolated from human faeces and was characterised using a polyphasic taxonomic approach. A phylogenetic analysis based on 16S rRNA gene sequences revealed that CBA7301T represented a member of the genus Bacteroides, in the family Bacteroidaceae. The similarity between the 16S rRNA gene sequence of CBA7301T and that of its most closely related species, Bacteroides faecichinchillae JCM 17102T, was 96.2 %, and the average nucleotide identity between these two strains was 77.9 %. The genome size was 6 782 182 bp, and the DNA G+C content was 42.5 mol%. Cells of CBA7301T were Gram-stain-negative, strictly anaerobic and rod-shaped. The optimal growth of this organism occurred at 30-35 °C, pH 7.0 and 0.5 % (w/v) NaCl. The respiratory quinone was menaquinone 10. The predominant polar lipids were phosphatidylethanolamine, phospholipids and aminophospholipids. The major cellular fatty acid was anteiso-C15 : 0. According to the results of the polyphasic taxonomic analysis, CBA7301T represents a novel species of the genus Bacteroides, which we named Bacteroides faecium sp. nov. The type strain is CBA7301T (=KCCM 43355T=ATCC TSD-227T).

Polyethylenimine linked with chitosan improves astaxanthin production in Haematococcus pluvialis.

Astaxanthin is receiving increasing interest as an antioxidant and high value-added secondary metabolite. Haematococcus pluvialis is the main source for astaxanthin production, and many studies are being conducted to increase the production of astaxanthin. In this study, we linked polyethylenimine (PEI) with chitosan to maintain astaxanthin-inducing ability while securing the recyclability of the inducer. Astaxanthin accumulation in H. pluvialis was induced to 86.4 pg cell-1 with the PEI-chitosan fiber (PCF) treatment prepared by cross-linking of 10 µM PEI and low molecular weight (MW) chitosan via epichlorohydrin. PEI concentration affected the astaxanthin accumulation, whereas the MW of chitosan did not. In addition, the PCF treatment in H. pluvialis increased the reactive oxygen species (ROS) content in cells, thereby upregulating the transcription of enzymes involved in astaxanthin biosynthesis. PCF can be reused multiple times with the maintenance of over 90% of the astaxanthin production efficiency. This study offers a reusable PCF stimulation strategy for enhancing natural astaxanthin content, and PCF treatment will easily increase the production scale or reduce production costs by using recyclability that is not available in current methods. KEY POINTS: • Polyethylenimine-chitosan fiber (PCF) was applied to Haematococcus pluvialis • PCF promotes astaxanthin accumulation by enhancing oxidative stress in H. pluvialis • PCF can be reused multiple times with maintaining over 90% production efficiency.

Simultaneous probing of dual intracellular metabolites (ATP and paramylon) in live microalgae using graphene oxide/aptamer nanocomplex.

The development of an intracellular metabolite imaging platform for live microorganisms has been a challenge in the study of microbes. Herein, we performed metabolite imaging in live microalgal cells using a graphene oxide (GO)/aptamer complex. The properties of the GO were characterized using dynamic light scattering (DLS) and atomic force microscopy (AFM), which were determined to have 140 ± 3 nm in mean diameter. An ATP-specific aptamer was mixed with GO to form a GO/aptamer complex, and the feasibility of the complex was tested in vitro. The high correlation between the fluorescence intensity and concentration of ATP was observed in the range 0-10 mM. Next, the feasibility of the complex was confirmed in vivo. Under both phototrophic and heterotrophic culture conditions, Euglena gracilis internalized the complex, and bright fluorescence was observed as the aptamer was bound to the target metabolite (ATP). The fluorescence intensity of cells was correlated to the ATP concentration in the cells. Imaging of dual intracellular metabolites (ATP and paramylon) was achieved by simply using two different aptamers (ATP-specific aptamer and paramylon-specific aptamer) together, showing the great potential of the complex as a dual-sensing/imaging platform. In addition, the GO/aptamer complex exhibited low cytotoxicity; the proliferation and viability of E. gracilis cells were not significantly affected by the complex. Our results suggested that this new imaging platform can be efficiently used for detecting dual intracellular metabolites in live microalgal cells.

Amination of cotton fiber using polyethyleneimine and its application as an adsorbent to directly remove a harmful cyanobacterial species, Microcystis aeruginosa, from an aqueous medium.

In the present study, we applied an adsorption-based strategy for the removal of a harmful cyanobacterial species, Microcystis aeruginosa, using cotton fiber. Considering the negatively charged surface properties of M. aeruginosa cells in aqueous phases, aminated cotton fibers were prepared through polyethyleneimine (PEI) modification on the pristine cotton fibers. The aminated surface properties of PEI-modified cotton fiber (PEI-cotton) were confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and potentiometric titration analyses. The pristine cotton fiber could not remove the M. aeruginosa cells, but the PEI-cotton could efficiently remove 98.7% of M. aeruginosa cells from the aqueous medium. In addition, removed cells could be observed on the sorbent surface by field emission scanning electron microscopy (FE-SEM) analysis. PEI-cotton fabricated in 3% PEI solution could remove M. aeruginosa cells (97.9%) more efficiently compared to that fabricated in 1% (82.1%) and 2% (86.2%) of PEI solutions. From the toxicity assessment of the PEI-cotton using Daphnia magna, negligible toxicity of PEI-cotton was confirmed. Our results indicate that the application of PEI-cotton fibers for the removal of M. aeruginosa cells could be suggested as a feasible, effective, and eco-friendly method of harmful algal bloom (HAB) control in water resources.

A strategic approach to apply bacterial substances for increasing metabolite productions of Euglena gracilis in the bioreactor.

Bacterial extracellular polymeric substances (EPS) are promising materials that have a role in enhancing growth, metabolite production, and harvesting efficiency. However, the validity of the EPS effectiveness in scale-up cultivation of microalgae is still unknown. Therefore, in order to verify whether the bacterial metabolites work in the scale-up fermentation of microalgae, we conducted a bioreactor fermentation following the addition of bacterial EPS derived from the marine bacterium, Pseudoalteromonas sp., to Euglena gracilis. Various culture strategies (i.e., batch, glucose fed-batch, and glucose and EPS fed-batch) were conducted to maximize metabolite production of E. gracilis in scale-up cultivation. Consequently, biomass and paramylon concentrations in the continuous glucose and EPS-treated culture were enhanced by 3.0-fold and 4.2-fold (36.1 ± 1.4 g L-1 and 25.6 ± 0.1 g L-1), respectively, compared to the non-treated control (12.0 ± 0.3 g L-1 and 6.1 ± 0.1 g L-1). Also, the supplementation led to the enhanced concentrations of α-tocopherols and total fatty acids by 3.7-fold and 2.8-fold, respectively. The harvesting efficiency was enhanced in EPS-supplemented cultivation due to the flocculation of E. gracilis. To the best of our knowledge, this is the first study that verifies the effect of bacterial EPS in scale-up cultivation of microalgae. Also, our results showed the highest paramylon productivity than any other previous reports. The results obtained in this study showed that the scale-up cultivation of E. gracilis using bacterial EPS has the potential to be used as a platform to guide further increases in scale and in the industrial environment. KEY POINTS: Effect of EPS on Euglena gracilis fermentation was tested in bioreactor scale. EPS supplement was effective for the paramylon, α-tocopherol, and lipid production. EPS supplement induced the flocculation of E. gracilis.

Application of electrical treatment on Euglena gracilis for increasing paramylon production.

Paramylon also called ß-1,3-glucan is a value-added product produced from Euglena gracilis. Recently, researchers have developed various strategies for the enhanced paramylon production, among which electrical treatment for microbial stimulation can be an alternative owing to the applicability to large-scale cultivation. In this study, we applied the electrical treatment for enhanced paramylon production and found the proper treatment conditions. Under the treatment with platinum electrodes at 10 mA, the paramylon production of treated cells was significantly increased about 2.5-fold, compared to those of the untreated cells, although the density of cells was maintained due to considerable stress. The size of treated cells became larger, possibly due to the increased level of paramylon production within the cells. Accordingly, the contents of glucose uptake, glucose-6-phosphate (G6P), glucose-1-phosphate (G1P), and uridine diphosphoglucose (UDPG) were shifted to appropriate states for the process of paramylon synthesis under the treatment. The increased level of transcripts encoding glucan synthase-like 2 (EgGSL2) was also confirmed via droplet digital PCR (ddPCR) under the treatment. Overall, this study makes a major contribution to research on electrical stimulation and provides new insights into E. gracilis metabolism like paramylon synthesis. KEY POINTS: • Electrical treatment induced the paramylon production and morphological change of Euglena gracilis. • The glucose uptake of E. gracilis was increased during the electrical treatment, fueling the paramylon synthesis.

Anaerocolumna sedimenticola sp. nov., isolated from fresh water sediment.

Strain CBA3638T was isolated from the Geum River sediment, Republic of Korea. The cells of strain CBA3638T were Gram-stain-positive, strictly anaerobic, rod-shaped, and 0.5-1.0 µm wide, and 4.0-4.5 µm long. Optimal growth occurred at 37 °C, pH 7.0, and 1.0% (w/v) NaCl. Based on the 16S rRNA gene sequence, the phylogenetic analysis showed that strain CBA3638T belongs to the genus Anaerocolumna in the family Lachnospiraceae, and is most closely related to Anaerocolumna cellulosilytica (94.6-95.0%). The DDH value with A. cellulosilytica SN021T showed 15.0% relatedness. The genome of strain CBA3638T consisted of one circular chromosome that is 5,500,435 bp long with a 36.7 mol% G + C content. The genome contained seven 16S-5S-23S rRNA operons and one antibiotic resistance-related transporter gene (mefA). Quinones were not detected. The predominant cellular fatty acids were C16:0 and C14:0 and the polar lipids were diphosphatidylglycerol, phosphatidylcholine, and uncharacterised polar lipids. Based on the polyphasic taxonomic analysis, we propose strain CBA3638T as a novel species in the genus Anaerocolumna, with the name Anaerocolumna sedimenticola sp. nov. The type strain is CBA3638T (= KACC 21652T = DSM 110663T).

Optimization of PTFE Coating on PDMS Surfaces for Inhibition of Hydrophobic Molecule Absorption for Increased Optical Detection Sensitivity.

Polydimethylsiloxane (PDMS) is a polymer widely used for fabrication and prototyping of microfluidic chips. The porous matrix structure of PDMS allows small hydrophobic molecules including some fluorescent dyes to be readily absorbed to PDMS and results in high fluorescent background signals, thereby significantly decreasing the optical detection sensitivity. This makes it challenging to accurately detect the fluorescent signals from samples using PDMS devices. Here, we have utilized polytetrafluoroethylene (PTFE) to inhibit absorption of hydrophobic small molecules on PDMS. Nile red was used to analyze the effectiveness of the inhibition and the absorbed fluorescence intensities for 3% and 6% PTFE coating (7.7 ± 1.0 and 6.6 ± 0.2) was twofold lower compared to 1% and 2% PTFE coating results (17.2 ± 0.5 and 15.4 ± 0.5). When compared to the control (55.3 ± 1.6), it was sevenfold lower in background fluorescent intensity. Furthermore, we validated the optimized PTFE coating condition using a PDMS bioreactor capable of locally stimulating cells during culture to quantitatively analyze the lipid production using Chlamydomonas reinhardtii CC-125. Three percent PTFE coating was selected as the optimal concentration as there was no significant difference between 3% and 6% PTFE coating. Intracellular lipid contents of the cells were successfully stained with Nile Red inside the bioreactor and 3% PTFE coating successfully minimized the background fluorescence noise, allowing strong optical lipid signal to be detected within the PDMS bioreactor comparable to that of off-chip, less than 1% difference.

Application of a polyethylenimine-modified polyacrylonitrile-biomass waste composite fiber sorbent for the removal of a harmful cyanobacterial species from an aqueous solution.

Cyanobacterial harmful algal blooms (Cyano-HABs) in water resources involving algal species such as Microcystis aeruginosa have become a serious environmental issue due to their severely negative effects. In the present study, an adsorption-based strategy was employed to control M. aeruginosa, with industrial waste-derived Escherichia coli biomass valorized to produce polyethylenimine-modified polyacrylonitrile-E. coli biomass composite fiber (PEI-PANBF). PEI-PANBF removed approximately 80% of M. aeruginosa cells from an aqueous solution without causing any cell damage. Interestingly, the thickness of PEI-PANBF had a strong influence on the efficiency of M. aeruginosa cell removal. In addition, PEI-PANBF simultaneously removed M. aeruginosa cells and their toxic secondary metabolite, microcystin-LR, from aqueous media. Thus, our proposed fiber represents a feasible utilization method of industrial waste biomass as a biosorbent for the control of Cyano-HABs.

Improvement of Euglena gracilis Paramylon Production through a Cocultivation Strategy with the Indole-3-Acetic Acid-Producing Bacterium Vibrio natriegens.

We investigated the putative effects on the growth and paramylon production of Euglena gracilis of cocultivation with Vibrio natriegensE. gracilis heterotrophically cocultivated with V. natriegens displayed significant increases in biomass productivity and paramylon content. In addition, the effects of the bacterial inoculum density and the timing of inoculation on the growth of E. gracilis were examined, to determine the optimal conditions for cocultivation. With the optimal deployment of V. natriegens, biomass productivity and paramylon content were increased by more than 20% and 35%, respectively, compared to those in axenic E. gracilis cultures. Interestingly, indole-3-acetic acid biosynthesized by V. natriegens was responsible for these enhancements of E. gracilis The morphology of cocultured E. gracilis cells was assessed. Paramylon granules extracted from the cocultivation were significantly larger than those from axenic culture. Our study showed that screening for appropriate bacteria and subsequent cocultivation with E. gracilis represented an effective way to enhance biomass and metabolite production.IMPORTANCEEuglena gracilis has attracted special interest due to its ability to excessively accumulate paramylon. Paramylon is a linear ß-1,3-glucan polysaccharide that is the principal polymer for energy storage in E. gracilis The polysaccharide features high bioactive functionality in the immune system. This study explored a new method to enhance the production of paramylon by E. gracilis, through cocultivation with the indole-3-acetic acid-producing bacterium Vibrio natriegens The enhanced production was achieved indirectly with the phytohormone-producing bacteria, instead of direct application of the hormone. The knowledge obtained in this study furthers the understanding of the effects of V. natriegens on the growth and physiology of E. gracilis.

Adsorptive removal of harmful algal species Microcystis aeruginosa directly from aqueous solution using polyethylenimine coated polysulfone-biomass composite fiber.

In recent times, the treatment of harmful algal blooms (HABs) became an important environmental issue to preserve and remediate water resources globally. In the present study, the adsorptive removal of harmful algal species Microcystis aeruginosa directly from an aqueous medium was attempted. Waste biomass (Escherichia coli) was immobilized using polysulfone and coated using the cationic polymer polyethylenimine (PEI) to generate PEI-coated polysulfone-biomass composite fiber (PEI-PSBF). The density of M. aeruginosa in an aqueous medium (BG11) was significantly decreased by treatment with PEI-PSBF. additionally, analysis using FE-SEM, confirmed that the removal of M. aeruginosa algal cells by PEI-PSBF was caused by the adsorption mechanism. According to the profiles of phosphorus for the algal cell growth in M. aeruginosa cultivating samples, we found that the adsorbed M. aeruginosa onto the PEI-PSBF lost their biological activity compared to the non-treated M. aeruginosa cells.

Comparative transcriptome analysis of Haematococcus pluvialis on astaxanthin biosynthesis in response to irradiation with red or blue LED wavelength.

The unicellular green microalga Haematococcus pluvialis has the highest content of the natural antioxidant, astaxanthin. Previously, it was determined that astaxanthin accumulation in H. pluvialis could be induced by blue-wavelength irradiation; however, the molecular mechanism remains unknown. The present study aimed to compare the transcriptome of H. pluvialis, with respect to astaxanthin biosynthesis, under the monochromatic red (660 nm) or blue (450 nm) light-emitting diode (LED) irradiation. Among a total of 165,372 transcripts, we identified 67,703 unigenes, of which 2245 and 171 were identified as differentially expressed genes (DEGs) in response to blue and red irradiation, respectively. Interestingly, expressional changes of blue light receptor cryptochromes were detected in response to blue and/or red LED irradiation in H. pluvialis, which may directly and indirectly regulate astaxanthin biosynthesis. In accordance with this observation, expression of the BKT and CHY genes, which are part of the downstream section of the astaxanthin biosynthetic pathway, was significantly upregulated by blue LED irradiation compared with their expression under control white irradiation. Contrastingly, they were downregulated by red LED irradiation. Our transcriptome study provided molecular insights that highlighted the different of responses of H. pluvialis to red and blue irradiation, especially for astaxanthin biosynthesis.

MST50 is involved in multiple MAP kinase signaling pathways in Magnaporthe oryzae.

Appressorium formation plays a critical role in Magnaporthe oryzae. Mst50 is an adapter protein of the Mst11-Mst7-Pmk1 cascade that is essential for appressorium formation. To further characterize its functions, affinity purification was used to identify Mst50-interacting proteins (MIPs) in this study. Two of the MIPs are Mst11 and Mst7 that are known to interact with Mst50 for Pmk1 activation. Surprisingly, two other MIPs are Mck1 and Mkk2 that are the upstream kinases of the Mps1 pathway. Domain deletion analysis showed that the sterile alpha-motif of Mst50 but not the Ras-association domain was important for its interaction with Mck1 and responses to cell wall and oxidative stresses. The mst50 mutant was reduced in Mps1 activation under stress conditions. MIP11 encodes a RACK1 protein that also interacted with Mck1. Deletion of MIP11 resulted in defects in cell wall integrity, Mps1 phosphorylation and plant infection. Furthermore, Mst50 interacted with histidine kinase Hik1, and the mst50 mutant was reduced in Osm1 phosphorylation. These results indicated that Mst50 is involved in all three MAPK pathways in M. oryzae although its functions differ in each pathway. Several MIPs are conserved hypothetical proteins and may be involved in responses to various signals and crosstalk among signaling pathways.

Enhancement of astaxanthin production using Haematococcus pluvialis with novel LED wavelength shift strategy.

Haematococcus pluvialis is a green microalga of particular interest, since it is considered the best potential natural source of astaxanthin, which is widely used as an additive for natural pigmentation. In addition, astaxanthin has recently garnered commercial interest as a nutraceutical, cosmetic, and pharmaceutical. However, producing astaxanthin from H. pluvialis necessitates separation with distinctive culture conditions, dividing between the microalgae growth and the astaxanthin production stages. Light-emitting diodes (LEDs) have emerged as a replacement for traditional light sources, and LED applications are now rapidly expanding to multiple areas in fields such as biotechnology. However, further detail application into microalgae biotechnology remains limited. In this study, we have attempted to establish new protocols based on the specific wavelength of LEDs for the cultivation and production of astaxanthin using H. pluvialis. Specifically, we applied red LEDs for microalgae cell growth and then switched to blue LEDs to induce astaxanthin biosynthesis. The result showed that astaxanthin productions based on a wavelength shift from red to blue were significantly increased, compared to those with continuous illumination using red LEDs. Furthermore, additional increase of astaxanthin production was achieved with simultaneous application of exogenous carbon with blue LED illumination. Our approach based on the proper manipulation of LED wavelengths upon H. pluvialis cell stages will enable the improvement of biomass and enhance astaxanthin production using H. pluvialis.

Eruca sativa and its flavonoid components, quercetin and isorhamnetin, improve skin barrier function by activation of peroxisome proliferator-activated receptor (PPAR)-α and suppression of inflammatory cytokines.

Atopic dermatitis, which is related to dermatologic disorders and is associated with skin barrier dysfunction, represents an epidemic problem demanding effective therapeutic strategies. In the present study, we showed that the treatment with Eruca sativa extract resulted in a significant increase in the transactivation activity of peroxisome proliferator-activated receptor (PPAR) response element such as PPAR-α and suppression in the expression of inflammatory cytokine and antimicrobial peptides. In addition, E. sativa extract promotes the expression of filaggrin related to skin barrier protection. Quercetin and isorhamnetin, flavonoids' constituents of E. sativa, also promoted PPAR-α activity. These results indicate that E. sativa extract may be an appropriate material for improving skin barrier function as a skin therapeutic agent for atopic dermatitis.

Enhancement of adsorption of cyanobacteria, Microcystisa aeruginosaby bacterial-based compounds.

In the present study, algicidal bacteria cultivated in an aqueous medium were utilized as a surface modification agent to develop an efficient adsorbent for the removal of Microcystis aeruginosa. The modification considerably enhanced M. aeruginosa cell removal efficiency. Moreover, the introduction of bio-compounds ensured specificity in the removal of M. aeruginosa. Additionally, the cyanotoxin release and acute toxicity tests demonstrated that the adsorption process using the developed adsorbent is environmentally safe. Furthermore, the practical feasibility of the adsorptive removal of M. aeruginosa was confirmed through cell removal tests performed using the developed adsorbent in a scaled-up reactor (50 L and 10 tons). In these tests, the effects of the adsorbent application type, water temperature, and initial cell concentration on the M. aeruginosa removal efficiency were evaluated. The results of this study provide novel insights into the valorization strategy of biological algicides repurposed as adsorbents, and provide practical operational data for effective M. aeruginosa removal in scaled-up conditions.

Chitosan-modified cotton fiber: An efficient and reusable adsorbent in removal of harmful cyanobacteria, Microcystis aeruginosa from aqueous phases.

In the present study, to remove harmful cyanobacterial species Microcystis aeruginosa from aqueous phases, adsorption-based strategy was utilized. For this strategy, the surface of cotton fiber was modified using chitosan molecules to develop a highly efficient and ecofriendly adsorbent in removal of Microcystis aeruginosa from aqueous solution. The pristine cotton fiber could not remove M. aeruginosa, while the chitosan-modified cotton (CS-m-Cotton) showed the 95% of cell removal efficiency within 12 h. The surface characteristics of chitosan-modified cotton compared to the pristine cotton fiber was examined by various surface analysis methods. In addition, the pre-treatment of pristine cotton using sodium hydroxide solution was an important factor for enhancement of chitosan modification efficiency on the cotton fiber. The developed chitosan-modified cotton fiber could be reusable for M. aeruginosa cell removal after the simple desorption treatment using ultrasonication in alkaline solution. During the repeated adsorbent regeneration and reuse, the chitosan-modified cotton maintained its M. aeruginosa removal efficiencies (>90%). From the acute toxicity assessment using the chitosan-modified cotton and, the measurements of chemical oxygen demand and microcystin level changes in the M. aeruginosa treatment process using the adsorbent, the environmental safety of the adsorption strategy using the developed adsorbent could be confirmed. Based on our results, the chitosan-modified cotton fiber could be proposed as an efficient and ecofriendly solution for remediation of harmful cyanobacterial species occurring water resources.

Effects of micro-sized biodegradable plastics on Microcystis aeruginosa.

Plethora of plastics are being used in current society, generating huge amounts of plastic waste. Non-biodegradability of conventional plastics is one of the main challenges to treat plastic waste. In an effort to increase the efficiency of plastic waste treatment, biodegradable plastics have gained attention. Although the use of biodegradable plastics has been increased, their potential effects on the environments are not fully elucidated yet. In this study, the impacts of micro-sized non-biodegradable plastic (i.e., polystyrene (PS)) and micro-sized biodegradable plastics (i.e., polycaprolactone (PCL) and polylactic acid (PLA)) on Microcystis aeruginosa were investigated. Regardless of microplastic (MP) types, MP treatments inhibited the growth of M. aeruginosa at the beginning (4 days) while significant dose-dependent effect was not observed in the range of 0.1 to 10 mg/L. However, after long-term exposure (12 days), micro-sized biodegradable plastics stimulated the growth of M. aeruginosa (up to 73 % increase compared to the control). The photosynthetic activity showed a similar trend to the cell growth. The MP treatments induced the production of extracellular polymeric substances (EPS). Indeed, micro-sized PCL and PLA stimulated the production of protein compounds in EPS. These might have affected the releases of chemicals from PCL and PLA, suggesting that the chemicals in biodegradable plastic leachates would promote the growth of M. aeruginosa in long-term exposure. The MP treatments also induced cyanotoxin (microcystin-LR) productions. Our results give a new insight into the cyanobacterial blooming and suggest a novel relationship between harmful algal blooms (HABs) and biodegradable plastics.

Enhancing poly(3-hydroxybutyrate) production in halophilic bacteria through improved salt tolerance.

Polyhydroxyalkanoates (PHA) have emerged as a promising bio-compound in the industrial application due to their potential to replace conventional petroleum-based plastics with sustainable bioplastics. This study focuses on Halomonas sp. YJPS3-3, a halophilic bacterium, and presents a novel approach to enhance PHA production by exploiting its salt tolerance toward PHA biosynthesis. Through gamma irradiation-induced mutants with enhanced salt tolerance from 15% NaCl to 20% NaCl, mutant halo6 showing a significant 11% increase in PHA yield, was achieved. Moreover, the mutants displayed not only higher PHA content but also remarkable cell morphology with elongation. In addition, this research unravels the genetic determinants behind the elevated PHA content and identifies a corresponding shift in fatty acid composition favoring PHA accumulation. This novel mutant obtained from gamma irradiation with enhanced salt tolerance in halophilic bacteria opens up new avenues not only for the bioplastic industry but also for applications in the production of high-value metabolites.

Green and efficient method to acquire high-value phycobiliprotein from microalgal biomass involving deep eutectic solvent-based ultrasound-assisted extraction.

Phycoerythrin (PE) is a phycobiliprotein holding great potential as a high-value food colorant and medicine. Deep eutectic solvent (DES)-based ultrasound-assisted extraction (UAE) was applied to extract B-PE by disrupting the resistant polysaccharide cell wall of Porphyridium purpureum. The solubility of cell wall monomers in 31 DESs was predicted using COSMO-RS. Five glycerol-based DESs were tested for extraction, all of which showed significantly higher B-PE yields by up to 13.5 folds than water. The DES-dependent B-PE extraction efficiencies were proposedly associated with different cell disrupting capabilities and protein stabilizing effects of DESs. The DES-based UAE method could be considered green according to a metric assessment tool, AGREEprep. The crude extract containing DES was further subjected to aqueous two-phase system, two-step ammonium sulfate precipitation, and ultrafiltration processes. The final purified B-PE had a PE purity ratio of 3.60 and a PC purity ratio of 0.08, comparable to the purity of commercial products.