Development of dual strain microalgae cultivation system for the direct carbon dioxide utilization of power plant flue gas.

This study aims to propose a biological system that allows for direct utilization of flue gas for carbon dioxide capture and utilization by microalgae. The strain Chlorella sp. ABC-001 is employed for its high growth rate as well as lipid and carbohydrate content. Toxicity tests showed that cell growth was unaffected by NO, but the presence of SO2 showed critical damage on cell growth. Hence, an extremophile alga, Galdieria sulphuraria 5587.1 was applied to build a dual-strain cultivation system to mitigate the effect of SO2 toxicity and increase CO2 capture efficiency. All SO2 was removed by Galdieria culture and the system exhibited stable growth from a simulated flue gas stream containing CO2, NO and SO2. Combined CO2 biofixation rate of 793 mg/L/d and lipid productivity of 113 mg/L/d was achieved. The results showed that this new cultivation system is a promising alternative for reducing CO2 emissions from power plants.

Simultaneous enhancement of lipid biosynthesis and solvent extraction of Chlorella using aminoclay nanoparticles.

Magnesium aminoclay nanoparticles (MgANs) exert opposing effects on photosynthetic microalgae by promoting carbon dioxide (CO2) uptake and inducing oxidative stress. This study explored the potential application of MgAN in the production of algal lipids under high CO2 concentrations. The impact of MgAN (0.05-1.0 g/L) on cell growth, lipid accumulation, and solvent extractability varied among three tested oleaginous Chlorella strains (N113, KR-1, and M082). Among them, only KR-1 exhibited significant improvement in both total lipid content (379.4 mg/g cell) and hexane lipid extraction efficiency (54.5%) in the presence of MgAN compared to those of controls (320.3 mg/g cell and 46.1%, respectively). This improvement was attributed to the increased biosynthesis of triacylglycerols and a thinner cell wall based on thin-layer chromatography and electronic microscopy, respectively. These findings suggest that using MgAN with robust algal strains can enhance the efficiency of cost-intensive extraction processes while simultaneously increasing the algal lipid content.

Microalgae-Based Biohybrid Microrobot for Accelerated Diabetic Wound Healing.

A variety of wound healing platforms have been proposed to alleviate the hypoxic condition and/or to modulate the immune responses for the treatment of chronic wounds in diabetes. However, these platforms with the passive diffusion of therapeutic agents through the blood clot result in the relatively low delivery efficiency into the deep wound site. Here, a microalgae-based biohybrid microrobot for accelerated diabetic wound healing is developed. The biohybrid microrobot autonomously moves at velocity of 33.3 µm s-1 and generates oxygen for the alleviation of hypoxic condition. In addition, the microrobot efficiently bound with inflammatory chemokines of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) for modulating the immune responses. The enhanced penetration of microrobot is corroborated by measuring fibrin clots in biomimetic wound using microfluidic devices and the enhanced retention of microrobot is confirmed in the real wounded mouse skin tissue. After deposition on the chronic wound in diabetic mice without wound dressing, the wounds treated with microrobots are completely healed after 9 days with the significant decrease of inflammatory cytokines below 31% of the control level and the upregulated angiogenesis above 20 times of CD31+ cells. These results confirm the feasibility of microrobots as a next-generation platform for diabetic wound healing.

Cell disruption and lipid extraction from Chlorella species for biorefinery applications: Recent advances.

Chlorella is a promising microalga for CO2-neutral biorefinery that co-produces drop-in biofuels and multiple biochemicals. Cell disruption and selective lipid extraction steps are major technical bottlenecks in biorefinement because of the inherent robustness and complexity of algal cell walls. This review focuses on the state-of-the-art achievements in cell disruption and lipid extraction methods for Chlorella species within the last five years. Various chemical, physical, and biological approaches have been detailed theoretically, compared, and discussed in terms of the degree of cell wall disruption, lipid extractability, chemical toxicity, cost-effectiveness, energy use, scalability, customer preferences, environment friendliness, and synergistic combinations of different methods. Future challenges and prospects of environmental-friendly and efficient extraction technologies are also outlined for practical applications in sustainable Chlorella biorefineries. Given the diverse industrial applications of Chlorella, this review may provide useful information for downstream processing of the advanced biorefineries of other algae genera.

Cell disruption and astaxanthin extraction from Haematococcus pluvialis: Recent advances.

The green microalga Haematococcus pluvialis is an excellent source of astaxanthin, a powerful antioxidant widely used in cosmetics, aquaculture, health foods, and pharmaceuticals. This review explores recent developments in cell disruption and astaxanthin extraction techniques applied using H. pluvialis as a model species for large-scale algal biorefinery. Notably, this alga develops a unique cyst-like cell with a rigid three-layered cell wall during astaxanthin accumulation (∼4% of dry weight) under stress. The thick (∼2 µm), acetolysis-resistant cell wall forms the strongest barrier to astaxanthin extraction. Various physical, chemical, and biological cell disruption methods were discussed and compared based on theoretical mechanisms, biomass status (wet, dry, and live), cell-disruption efficacy, astaxanthin extractability, cost, scalability, synergistic combinations, and impact on the stress-sensitive astaxanthin content. The challenges and future prospects of the downstream processes for the sustainable and economic development of advanced H. pluvialis biorefineries are also outlined.

Supply of proton enhances CO electrosynthesis for acetate and volatile fatty acid productions.

The microbial electrosynthesis is a platform to supply protons and electrons to improve the conversion efficiency and production rate for the valorization of C1 gas. This study examined proton migration and electron transfer of the electrode and microbe by using various external parameters in the electrosynthesis of CO. The CO electrosynthesis achieved almost double of coulombic efficiency than the conventional CO2 electrosynthesis. The maximum volumetric acetate production rate was 0.71 g/L/day in the BES, which was 2-6 times higher than reported elsewhere. These results show that the efficient proton migration and electron transfer can enhance the productivity and conversion efficiency of the biological CO conversion in a bioelectrochemical system.

Correlation of microbial community with salinity and nitrogen removal in an anammox-based denitrification system.

Anaerobic ammonium oxidation (anammox), a low-energy-consuming technology, can be used to remove nitrogen from industrial saline wastewater. However, high salinity inhibits anammox microbial activity. This study investigated the effect of salinity on nitrogen removal performance and microbial community structure. The experiment used an up-flow anammox reactor fed with synthetic wastewater with salinity increased from 0.5 to 2.5%. Results indicated that 80% nitrogen removal efficiency can be achieved at 2% salinity with a nitrogen loading rate of 2.0 kg-N/m3/d. Anammox performance significantly deteriorated at 2.5% salinity. High-throughput sequencing revealed that Planctomycetes (representative anammox bacteria) increased with salinity, replacing Proteobacteria (representative heterotrophic denitrifying bacteria) in the microbial community. qPCR analysis indicated that relative abundance of "Candidatus Kuenenia" within anammox bacteria increased from 3.96 to 83.41%, corresponding to salinity of 0.5-2.0%, and subsequently decreased to 63.27% at 2.5% salinity, correlating with nitrogen-removal performance. Thus, anammox has potential in nitrogen removal from wastewater with salinity up to 2%.

Enabling anoxic acetate assimilation by electrode-driven respiration in the obligate aerobe, Pseudomonas putida.

This study examined the obligate aerobe, Pseudomonas putida, using acetate as the sole carbon and energy source, and respiration via an anode as the terminal electron acceptor under anoxic conditions. P. putida showed significantly different acetate assimilation in a closed-circuit microbial fuel cell (CC-MFC) compared to an open circuit MFC (OC-MFC). More than 72% (2.6 mmol) of acetate was consumed during 84 hrs in the CC-MFC in contrast to the no acetate consumption observed in the OC-MFC. The CC-MFC produced 150 µA (87 C) from acetate metabolization. Electrode-based respiration reduced the NADH/NAD+ ratio anaerobically, which is similar to the aerobic condition. The CC-MFC showed significantly higher acetyl-CoA synthetase activity than the OC-MFC (0.028 vs. 0.001 µmol/min/mg), which was comparable to the aerobic condition (circa 60%). Overall, electrode-based respiration enables P. putida to metabolize acetate under anoxic conditions and provide a platform to regulate the bacterial redox balance without oxygen.

Recent developments and key barriers to microbial CO2 electrobiorefinery.

The electrochemical conversion of CO2 can include renewable surplus electricity storage and CO2 utilisation. This review focuses on the microbial CO2 electrobiorefinery based on microbial electrosynthesis (MES) which merges electrochemical and microbial conversion to produce biofuels and higher-value chemicals. In this review, recent developments are discussed about bioelectrochemical conversion of CO2 into biofuels and chemicals in MES via microbial CO2-fixation and electricity utilisation reactions. In addition, this review examines technical approaches to overcome the current limitations of MES including the following: engineering of the biocathode, application of electron mediators, and reactor optimisation, among others. An in-depth discussion of strategies for the CO2 electrobiorefinery is presented, including the integration of the biocathode with inorganic catalysts, screening of novel electroactive microorganisms, and metabolic engineering to improve target productivity from CO2.

Photoautotrophic hydrogen production of Rhodobacter sphaeroides in a microbial electrosynthesis cell.

Conventional photoheterotrophic H2 production by purple sulfur bacteria requires additional organic substrates as the carbon and energy sources. This study examined the novel photoautotrophic H2 production of Rhodobacter sphaeroides with concomitant CO2 uptake in microbial electrosynthesis (MES). Under an applied potential of -0.9 V vs. Ag/AgCl to the cathode, Rhodobacter sphaeroides produced hydrogen with CO2 as the sole carbon source under illumination. The initial planktonic cells decreased rapidly in suspension, whereas biomass formation on the cathode surface increased gradually during MES operation. The electron and carbon flow under photoautotrophic conditions in MES were estimated. Glutamate, as the nitrogen source, enhanced hydrogen production significantly (328 mL/L/day) compared to NH4Cl (67 mL/L/day) during seven days of operation. The photoautotrophic condition with 6000 lx presented CO2 consumption and simultaneous biomass formation on the cathode electrode. MES-driven electron and proton transfer enabled the simultaneous production of hydrogen and CO2 uptake.

Effects of Nitrogen Supplementation Status on CO2 Biofixation and Biofuel Production of the Promising Microalga Chlorella sp. ABC-001.

The use of microalgal biomass as feedstock for biofuels has been discussed for decades as it provides a sustainable approach to producing fuels for the future. Nonetheless, its feasibility has not been established yet and various aspects of biomass applications such as CO2 biofixation should also be explored. Therefore, in this study, the CO2 biofixation and lipid/carbohydrate production potential of Chlorella sp. ABC-001 were examined under various nitrogen concentrations. The highest biomass productivity and CO2 biofixation rate of 0.422 g/l/d and 0.683 g/l/d, respectively, were achieved under a nitrogen-rich condition (15 mM nitrate). Carbohydrate content was generally proportional to initial nitrate concentration and showed the highest value of 41.5% with 15 mM. However, lipid content showed an inverse relationship with nitrogen supplementation and showed the highest value of 47.4% with 2.5 mM. In consideration as feedstock for biofuels (bioethanol, biodiesel, and biogas), the sum of carbohydrate and lipid contents were examined and the highest value of 79.6% was achieved under low nitrogen condition (2.5 mM). For lipid-based biofuel production, low nitrogen supplementation should be pursued. However, considering the lower feasibility of biodiesel, pursuing CO2 biofixation and the production of carbohydrate-based fuels under nitrogenrich condition might be more rational. Thus, nitrogen status as a cultivation strategy must be optimized according to the objective, and this was confirmed with the promising alga Chlorella sp. ABC-001.

Biocompatible liquid-type carbon nanodots (C-paints) as light delivery materials for cell growth and astaxanthin induction of Haematococcus pluvialis.

In this study, we aimed to demonstrate the feasibility of the application of biocompatible liquid type fluorescent carbon nanodots (C-paints) to microalgae by improving microalgae productivity. C-paints were prepared by a simple process of ultrasound irradiation using polyethylene glycol (PEG) as a passivation agent. The resulting C-paints exhibited a carbonyl-rich surface with good uniformity of particle size, excellent water solubility, photo-stability, fluorescence efficiency, and good biocompatibility (<10.0 mg mL-1 of C-paints concentration). In the practical application of C-paints to microalgae culture, the most effective and optimized condition leading to growth promoting effect was observed at a C-paints concentration of 1.0 mg mL-1 (>20% higher than the control cell content). A C-paints concentration of 1-10.0 mg mL-1 induced an approximately >1.8 times higher astaxanthin content than the control cells. The high light delivery effect of non-cytotoxic C-paints was applied as a stress condition for H. pluvialis growth and was found to play a major role in enhancing productivity. Notably, the results from this study are an essential approach to improve astaxanthin production, which can be used in various applications because of its therapeutic effects such as cancer prevention, anti-inflammation, immune stimulation, and treatment of muscle-soreness.

Enhancement of astaxanthin production by Haematococcus pluvialis using magnesium aminoclay nanoparticles.

Improving the content and production of high-value ketocarotenoid pigments is critical for the commercialization of microalgal biorefineries. This study reported the use of magnesium aminoclay (MgAC) nanoparticles for enhancement of astaxanthin production by Haematococcus pluvialis in photoautotrophic cultures. Addition of 1.0 g/L MgAC significantly promoted cellular astaxanthin biosynthesis (302 ± 69 pg/cell), presumably by inducing tolerable oxidative stress, corresponding to a 13.7-fold higher production compared to that in the MgAC-untreated control (22 ± 2 pg/cell). The lipid content and cell size of H. pluvialis improved by 13.6- and 2.1-fold, respectively, compared to that of the control. Despite reduced cell numbers, the overall astaxanthin production (10.3 ± 0.4 mg/L) improved by 40% compared to the control (7.3 ± 0.6 mg/L), owing to improved biomass production. However, an MgAC dosage above 1.0 g/L inhibited biomass production by inducing electrostatic cell wall destabilization and aggregation. Therefore, MgAC-induced stimulation of algae varies widely based on their morphological and physiological characteristics.

Recovery of Astaxanthin-Containing Oil from Haematococcus pluvialis by Nano-dispersion and Oil Partitioning.

The feasibilities of cell disruption by homogenization-assisted high-pressure nano-dispersion and recovery of astaxanthin-containing oil by oil partitioning in oil-acetone-water solution were examined. The total fatty acid content of Haematococcus pluvialis was 414.6 mg/g cell, and the astaxanthin content was 4.4% of oil. Extra oil was added to the solution in order to recover oil through instability of dispersion status instead of solvent evaporation. A total amount of energy of 0.34 kWh/L was consumed for acetone evaporation at 50 °C, whereas fully 1.86 kWh/L of energy for water evaporation was consumed. When soybean oil was added to the solution after partial acetone evaporation, the oil-recovery yield was 97.8%, while the yield after full evaporation was 97.6% in 10-g/L solution. However, the energy consumed for partial evaporation (0.29 kWh/L) was much lower than that for full evaporation (0.40 kWh/L). When H. pluvialis oil was added to the solution after partial evaporation, the oil-recovery yield decreased to 90.6% due to the impurity of crude H. pluvialis oil in 10-g/L solution. Methods such as refining of H. pluvialis oil, increase of microalgae dosage for cell disruption, and increase of the injection amount of extra oil can help to enhance oil recovery.

Rapid induction of edible lipids in Chlorella by mild electric stimulation.

In this work, a new stress-based method for rapid induction of triacylglycerol (TAG) and total and polyunsaturated fatty acid accumulations in Chlorella sp. by mild electric stimulation is presented. When a cathodic current of 31 mA (voltage: 4 V) was applied to the algal cells for 4 h, the TAG content of the electro-treated cells was sharply increased to a level 2.1 times that of the untreated control. The contents of the polyunsaturated linoleic (C18:2n6) and linolenic (C18:3n3) acids in the electro-treated cells were also 36 and 57% higher than those in the untreated cells, respectively. Cyclic voltammetry and various biochemical analyses indicate that TAG and fatty acid formations are electro-stimulated via de novo fatty acid biosynthesis and metabolic transformation in the Chlorella cells.

High-efficiency cell disruption and astaxanthin recovery from Haematococcus pluvialis cyst cells using room-temperature imidazolium-based ionic liquid/water mixtures.

Energy-saving, high-efficiency cell disruption is a critical step for recovery of thermolabile antioxidant astaxanthin from Haematococcus pluvialis cyst cells of rigid cell-wall structure. In this study, as room-temperature green solvents, 10 types of 1-ethyl-3-methylimidazolium ([Emim])-based ionic liquids (ILs) were compared and evaluated for their abilities to disrupt H. pluvialis cyst cells for astaxanthin/lipid extraction. Among the 10 ILs tested, 3 [Emim]-based ILs with HSO4, CH3SO3, and (CF3SO2)2N anions were selected based on astaxanthin/lipid extraction performance and synthesis cost. When pretreated with IL/water mixtures, intact cyst cells were significantly torn, broken or shown to release cytoplasmic components, thereby facilitating subsequent separation of astaxanthin/lipid by hexane. However, excess IL pretreatments at high temperature/IL dosages and longer incubation times significantly deteriorated lipid and/or astaxanthin. Under optimized mild conditions (6.7% (v/v) IL in water solution, 30 °C, 60 min), almost complete astaxanthin recoveries (>99%) along with moderate lipid extractions (∼82%) could be obtained.

Studies on mass production and highly solar light photocatalytic properties of gray hydrogenated-TiO2 sphere photocatalysts.

In this paper, it is first reported that gray hydrogenated TiO2 sphere photocatalysts (H-TiO2) with high reactivity to solar light are mass produced within a few minutes using an underwater discharge plasma modified sol-gel method at room temperature and atmospheric pressure. This plasma modified system is an easy one-step in-situ synthetic process and the crystallinity, hydrogenation, and spherical structure of H-TiO2 are achieved by the synergy effect between the continuous reaction of highly energetic atomic and molecular species generated from the underwater plasma and surface tension of water. The resultant H-TiO2 demonstrated high anatase/rutile bicrystallinity and extended optical absorption spectrum from the ultraviolet (UV) to visible range. Furthermore, various defects including oxygen vacancies and hydroxyl species on the TiO2 surface permitted the enhancement of the photocatalytic performance. It was demonstrated that H-TiO2 photocatalysts showed significant degradation efficiencies for reactive black 5 (RB 5), rhodamine B (Rho B), and phenol (Ph) under solar light irradiation, up to approximately 5 times higher than that of commercial anatase TiO2 (C-TiO2), which resulted in good water purification. Notably, it was also possible to cultivate HepG2 cells using such well-purified water (to degrees up to 76%), with minimal cytotoxicity. Considering all these results, we believe that this novel plasma technology is promising for important environmental applications.

Effects of Sparassis crispa in Medical Therapeutics: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

In this study, we investigated the therapeutic potential and medical applications of Sparassis crispa (S. crispa) by conducting a systematic review of the existing literature and performing a meta-analysis. The original efficacy treatment of the mushroom extract is considered primarily and searched in electronic databases. A total of 623 articles were assessed, 33 randomized controlled experiments were included after the manual screening, and some papers, review articles, or editorials that did not contain data were excluded. A comparative standard means difference (SMD) and a funnel plot between control and S. crispa groups were used as parameters to demonstrate the beneficial effects of S. crispa for diabetes and cancer treatment, as well as anti-inflammatory, anti-fungal and antioxidant activities. The meta-analysis was carried out using Review Manager 5.1 software. Although for therapeutic diabetes there was heterogeneity in the subgroup analysis (I² = 91.9%), the overall results showed statistically significant SMDs in major symptoms that decreased serum insulin levels (SMD = 1.92, 95% CI (1.10, 2.75), I² = 0%), wound rates (SMD = 3.55 (2.56, 4.54), I² = 40%) and contributions to an increase in nutrient intake content (SMD = 0.32 (-0.15, 0.78), I² = 0%). Simultaneously, the study confirmed the utility of S. crispa treatment in terms of not only anti-cancer activity (reduction of tumor activity and survival of cancer cells I² = 42 and 34%, respectively) but also anti-inflammatory, anti-fungal and antioxidant activities (I² = 50, 44, and 10%, respectively). Our findings suggest that S. crispa extracts are useful for prevention and treatment of human diseases and might be the best candidates for future medicines.

Co-culture-based biological carbon monoxide conversion by Citrobacter amalonaticus Y19 and Sporomusa ovata via a reducing-equivalent transfer mediator.

The biological conversion of carbon monoxide (CO) has been highlighted for the development of a C1 gas biorefinery process. Despite this, the toxicity and low reducing equivalent of CO uptake make biological conversion difficult. The use of synthetic co-cultures is an alternative way of enhancing the performance of CO bioconversion. This study evaluated a synthetic co-culture consisting of Citrobacter amalonaticus Y19 and Sporomusa ovata for acetate production from CO. In this consortium, the CO2 and H2 produced by the water-gas shift reaction of C. amalonaticus Y19, were utilized further by S. ovata. Higher acetate production was achieved in the co-culture system compared to the monoculture counterparts. Furthermore, syntrophic cooperation via various reducing equivalent carriers provided new insights into the synergistic metabolic benefits with a toxic and refractory substrate, such as CO. This study also suggests an appropriate model for examining the syntrophic interaction between microbial species in a mixed community.