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The production of biohythane, a combination of energy-dense hydrogen and methane, from the anaerobic digestion of low-cost organic wastes has attracted attention as a potential candidate for the transition to a sustainable circular economy. Substantial research has been initiated to upscale the process engineering to establish a hythane-based economy by addressing major challenges associated with the process and product upgrading. This review provides an overview of the feasibility of biohythane production in various anaerobic digestion systems (single-stage, dual-stage) and possible technologies to upgrade biohythane to hydrogen-enriched renewable natural gas. The main goal of this review is to promote research in biohythane production technology by outlining critical needs, including meta-omics and metabolic engineering approaches for the advancements in biohythane production technology.

Abstract Microcystins (MCs) are toxins produced by cyanobacteria commonly found in harmful algal blooms (HABs). Due to their toxicity to humans and other organisms, the World Health Organization (WHO) set a guideline of 1 µg L− 1 for microcystin-leucine-arginine (MC-LR) in drinking water. However, current analytical techniques for the detection of MC-LR such as liquid chromatography-mass spectrometry (LC-MS) and ELISA are costly, bulky, time-consuming, and mostly conducted in a laboratory, requiring highly trained personnel. An analytical method that can be used in the field for rapid determination is essential. In this study, an Anti-MC-LR/MC-LR/Cysteamine coated screen-printed carbon electrode (SPCE) biosensor was newly developed to detect MC-LR, bioelectrochemically, in water. The functionalization of the electrode surface was confirmed with surface characterization methods. The sensor performance was evaluated by electrochemical impedance spectroscopy (EIS), obtaining a linear working range of MC-LR concentrations between 0.1 and 100 µg L− 1 with a limit of detection (LOD) of 0.69 ng L− 1. Natural water samples experiencing HABs were collected and analyzed using the developed biosensor, demonstrating the excellent performance of the biosensor with a relative standard deviation (RSD) of 0.65%. The interference tests showed a minimal error and RSD values against other common MCs and possible coexisting ions found in water. The biosensor showed acceptable functionality with a shelf life of up to 12 weeks. Overall, the Anti-MC-LR/MC-LR/Cysteamine/SPCE biosensors can be an innovative solution with characteristics that allow for in situ, low-cost, and easy-to-use capabilities which are essential for developing an overarching and integrated “smart” environmental management system.

Photo-biohydrogen by microalgae is attractive sustainable energy caused by the utilization of solar energy and water. However, due to oxygen (O2) sensitive hydrogenase (HydA) activity, effective control of O2 and light intensity is critical for achieving sustainable photosynthetic hydrogen (H2) production. Here we demonstrate continuous algal H2 production using acetate-enriched fermenter effluent, achieving the complete O2 cessation without sulfur depletion. Average H2 production of 108 ± 4 μmol L−1 for Chlamydomonas reinhardtii and 88 ± 7 μmol L−1 for Chlorella sorokiniana at 100 μmol m−2 s−1 were observed for 15 days, respectively. The highest light energy to H2 energy conversion efficiency (LHCE) of 1.61% for C. reinhardtii and 1.06% for C. Sorokiniana was obtained under low light intensity (50 μmol m−2 s−1) but the LHCE decreased with the increase of light intensity followed by photoinhibition, which led to a decrease of HydA activity and H2 production. Low H2 production was observed at 50 μmol m−2 s−1 under the highest LHCE, in which microalgae exhibited photoinhibition biomass growth kinetics to produce chlorophyll a (Chl a) for electron generation. These results demonstrate that light is a feasible strategy for producing electron for H2 production under anoxygenic photosynthesis.

Microalgae shows a high potential to produce biofuel and forward osmosis (FO) has been proposed as a promising dewatering process for algal biomass separation from water. However, the effect of reverse salt flux (RSF) on algal biomass during the dewatering process using FO has not been completely explored. This study was to investigate the effect of different types of salt and their concentrations on algal biomass in terms of conductivity, settling velocity, and lipid contents in FS during a simulated FO-driven dewatering of Chlorella vulgaris microalgae. Three draw solution (DS) salts (NaCl, KCl and NH4Cl) were evaluated in RSF-simulating batch tests. The salt diffusion from the DS to the algal feed solution (FS) caused a static growth of algal biomass while increasing lipid content up to 14.8% at 8 mM NH4Cl. With the addition of the different salts, pH was maintained to the optimal algal thriving range (7.2–10.6), but the presence of salt stressed the algal cells and inhibited photosynthesis and algal growth within the experimental conditions. The settling velocity of the algal cells improved with the increase of salt content from 8 to 80 mM of each DS. It seemed that cell division could be accelerated in the presence of NH4Cl, and microscopic images showed a change in the algal cell size distribution, which may negatively affect algal settleability. DS salt in an FO-algal harvesting system should be selected based on the final algal properties and constituents required.

Renewable energy production using microorganisms is one of the challenging issues for environmental sustainability. Algal hydrogen (H2) production has often been achieved by sulfur (S) and chloride ion (Cl−) deprivation in a growth medium; however, it may not be realistic to control S or Cl− concentrations in natural sources (e.g., wastewater). In this study, two different green algal species, Chlamydomonas reinhardtii and Chlorella sorokiniana were selected and their photosynthetic activities were compared with different acetate/Cl− ratios both in batch and continuous modes. At 150 of acetate/Cl− ratio, the H2 production rates were 0.25–0.33 μmol L−1 min−1 for C. sorokiniana and 0.20–0.38 μmol L−1 min−1 for C. reinhardtii, respectively. The hydrogenase (HydA) reactivation and photosystem II (PSII) inhibitor test revealed that biohydrogen production by algae is due to photosynthetic activity. It was found that maintaining acetate/Cl− ratios greater than 60–100 leads to continuous O2 depletion and thus renewable H2 production for both algal species. Molecular dynamics (MD) simulations of hydrogen bonding between Yz and His190 in PSII supported O2 inhibition using acetate. Using fermenter effluents, C. sorokiniana and C. reinhardtii showed a successful continuous H2 production of ~80 μmol L−1 and ~95 μmol L−1, respectively, for 15 days.

In this study, a novel molybdenum disulfide (MoS(2)) nano-carbon (NC) coated cathode was developed for hydrogen production in a microbial electrolysis cell (MEC), while treating simulated urine with 2–6 times dilution (conductivity 600 mg L(−1) NH(3)-N) can adversely affect the biofilm architecture and the bacterial activity at the anode of the MEC. Exoelectrogenic bacteria for this system at the anode were identified as Tissierella (Clostridia) and Bacteroidetes taxa. Maximum ammonia-nitrogen (NH(3)-N) and phosphorus (PO(4)(3−)-P) removal were 68.7 and 98.6%, respectively. This study showed that the newly fabricated MoS(2)-NC cathode can be a cost-effective alternative to the Pt cathode for renewable bioelectrochemical hydrogen production from urine.

Oil spills are a major threat to the marine ecosystem, requiring immediate solutions to remove spilled oil from oceanic environments. In this study, we report a superhydrophobic molybdenum disulfide (MoS2) coated polydimethylsiloxane (PDMS) sponge and demonstrate its high proficiency in spilled oil recovery and oil spill detection based on oil-water separation ability. This novel oil sorbent is fabricated by a simple dip-coating to incorporate MoS2 flakes into PDMS sponge. The optimized MoS2-sponge displays a water contact angle of >152°, demonstrating excellent superhydrophobicity and high oil absorption (>97 wt%) for a variety of oils, including vegetable oil and fuel waste. Moreover, the material retains excellent oil absorption capability upon repetitive compression cycles. The versatility of this novel sorbent has been extended for the real-time spontaneous detection of oils by taking advantage of electrically conductive MoS2 layers.

A novel As(III) sensor was developed by co-electrodepositing a Fe-Chitosan composite to a screen-printed carbon electrode sensor. The newly developed Fe-Chitosan-coated carbon electrode sensor exhibited successful As(III) detection in mining wastewater and soil leachate using square wave anodic stripping voltammetry (SWASV). A noticeable peak was observed at +0.15 V associated with stripping current of As(III) for both real wastewater samples. The calibration curves showed strong correlations with respect to As(III) with the limit of detection (LOD) of 1.12 ppb for mining wastewater and 1.01 ppb for soil leachate, respectively. Lower relative standard deviations (RSD) were obtained with 2.91% for mining wastewater and 4.54% for soil leachate during repeated measurements (n = 8), respectively, indicating enhanced stability for As(III) detection in the real wastewater application. The interference from copper and other metal ions (e.g., Zn(II), Pb(II) and Cd(II)) was found negligible for As(III) detection using the polymer modified Fe-coated electrode sensor, which suggests that the Fe-chitosan composite imparted the selectivity in the presence of other metal ions to As(III) detection in complex water matrix. These results demonstrate the applicability of a novel Fe-Chitosan-coated carbon electrode sensor to real wastewater As(III) pollution monitoring with the acceptable range of characteristics.

Recent advancements in MoS2 nanofilms have aided in the development for important water-related environmental applications. However, a MoS2 nanofilm-coated sensor has yet to have been applied for heavy metal detection in water-related environmental samples. In this study, a novel vertically aligned two-dimensional (2D) MoS2 (edge exposed) nanofilm was applied for in situ lead ion (Pb2+) detection. The developed sensor showed an excellent linear relationship toward Pb2+ between 0 and 20 ppb at -0.45 V vs Ag/AgCl using square wave anodic stripping voltammetry (SWASV) with the improved limit of detection (LOD) of 0.3 ppb in a tap water environment. The vertically aligned 2D MoS2 sensor exhibited improved detection sensitivity (2.8 folds greater than a previous metallic [Bi] composite electrode) with lower relative standard deviation for repetitive measurements (n = 11), indicating enhanced reproducibility for Pb2+ detection. The vertically aligned 2D MoS2 layers exhibited 2.6 times higher sensitivity than horizontally aligned 2D MoS2 (basal plane exposed). Density functional theory calculations demonstrated that adsorption energy of Pb on the MoS2 side edge was much higher (4.11 eV) than those on the basal plane (0.36 and 0.07 eV). In addition, the band gap center of vertical MoS2 was found to be higher than the Pb2+ → Pb reduction potential level and capable of reducing Pb2+. Overall, the newly developed vertically aligned 2D MoS2 sensor showed excellent performance for detecting Pb2+ in a real drinking water environment with good reliability.

Effective remediation of bilge water, a shipboard oily liquid waste, is important for both commercial and military vessels due to the domestic and international regulations. In this study, bilge water was used as a substrate for exoelectrogenic bacteria and biodegradation of bilge water and concurrent electricity generation were investigated using Pseudomonas putida ATCC 49128 in single chamber microbial fuel cells (MFCs). To enhance bioavailability of the bilge water, two types of surfactants were added (100 ppm) into the oily wastewater containing 0.1% standard bilge mix (SBM) and their impacts on electricity production were evaluated under various conditions. Anionic surfactant (sodium dodecyl sulfate, SDS) addition increased soluble chemical oxygen demand (SCOD) by forming micelle, producing maximum power density of 225.3 ± 3.2 mW m−2. However, the MFC with nonionic surfactant (Triton X-100) produced only 2.3 ± 0.1 mW m−2 due to no enhancement on biodegradable SCOD. A high NaCl concentration (100–500 mM) adversely affected power production due to decrease in available SCOD caused by emulsion coalescence. This is a first study to use surfactants to enhance bioavailability of non-biodegradable oily wastewater in a single chamber MFC.

A novel modified nanoporous bismuth electrode (modified-NPBiE) sensor was prepared by consecutive procedures which consist of bismuth (Bi) and tin (Sn) electroplating, thermal treatment for alloying Bi-Sn film, and selective chemical dealloying of Sn. The newly prepared modified-NPBiE sensor exhibited improved lifetime (2.7 times longer than a conventional nanoporous Bi-filmed electrode with over 40 repeated measurements) sensor with lower relative standard deviation (RSD), indicating enhanced stability and reproducibility for heavy metal detection. Using square wave anodic stripping voltammetry (SWASV), two noticeable peaks were observed at −0.65 V and −0.45 V associated with stripping currents of Cd2+ and Pb2+ in 0.1 M acetate buffer solution at pH 4.6, respectively. The calibration curves showed strong correlations with respect to various concentrations of Cd2+ and Pb2+ with the limit of detection (LOD) of 1.3 ppb for Cd2+ and 1.5 ppb for Pb2+. The newly modified-NPBiE sensor was then successfully applied for detecting Cd2+ and Pb2+ in a tap water environment and exhibited an acceptable performance for measuring heavy metals with a good reliability.

A novel Au nanoparticle (AuNP)-biopolymer coated carbon screen-printed electrode (SPE) sensor was developed through the co-electrodeposition of Au and chitosan for mercury (Hg) ion detection. This new sensor showed successful Hg2+ detection in landfill leachate using square wave anodic stripping voltammetry (SWASV) with an optimized condition: a deposition potential of −0.6 V, deposition time of 200 s, amplitude of 25 mV, frequency of 60 Hz, and square wave step voltage of 4 mV. A noticeable peak was observed at +0.58 V associated with the stripping current of the Hg ion. The sensor exhibited a good sensitivity of ~0.09 μA/μg (~0.02 μA/nM) and a linear response over the concentration range of 10 to 100 ppb (50–500 nM). The limit of detection (LOD) was 1.69 ppb, which is significantly lower than the safety limit defined by the United States Environmental Protection Agency (USEPA). The sensor had an excellent selective response to Hg2+ in landfill leachate against other interfering cations (e.g., Zn2+, Pb2+, Cd2+, and Cu2+). Fifteen successive measurements with a stable peak current and a lower relative standard deviation (RSD = 5.1%) were recorded continuously using the AuNP-biopolymer-coated carbon SPE sensor, which showed excellent stability, sensitivity and reproducibility and consistent performance in detecting the Hg2+ ion. It also exhibited a good reliability and performance in measuring heavy metals in landfill leachate.

Bioaugmenting lignocellulose digestion with potent lignocellulolytic microbiomes (LMs) facilitates efficient biomethanation. Assessing the metabolic roles of microbial communities of the LMs and their complex interactions with the indigenous anaerobic digester microbiome is pivotal in implementing bioaugmentation. Multiple meta-omics are the frontline approaches to investigating gene functions, metabolic roles, and the ecological niches of LMs.

In this study, sliver (Ag) and gold (Au) nanoparticles (NPs) were embedded on poly (acrylic acid) (PAA)/poly (allylamine) hydrochloride (PAH) hydrogel fibers for improved electrochemical oxidation (EO) of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) removal. The NPs-loaded PAA/PAHs shows the better charge transport compared to the ceramic nanofiber membranes (CNM) electrodes. At 10 mA cm

Trace minerals play an essential role in methane production via anaerobic digestion (AD). It is important to monitor Ni(II) and Co(II) concentrations and the Ni/Co concentration ratio for the rapid diagnosis of the ecological status or activity of methanogens in AD. Electrochemical detection of Ni(II) and Co(II) was investigated by coating the Bi-chitosan nanocomposite on a glassy carbon electrode (GCE) via the electrodeposition technique. A square-wave adsorptive cathodic stripping voltammetry technique (SWAdCSV) was applied and optimized when dimethylglyoxime (DMG) was used as the chelating agent for Ni(II) and Co(II) measurements. The SWAdCSV results showed that the current peaks for Co(II) detection are 6.1 times greater than the current peaks for Ni(II) measurements, probably due to the different affinity of DMG molecules between Ni(II) and Co(II). DMG molecules demonstrated higher selectivity toward Co(II) cations compared to Ni(II). The modified Bi-chitosan GCE developed in this study showed a relatively wide range of the Ni(II) and Co(II) concentrations (2–100 µg L−1) with a limit of detection of 3.6 µg L−1 for Ni(II) and 2.4 µg L−1 for Co(II), respectively. The developed sensor was applied to Ni(II) and Co(II) spiked natural water samples and showed good performance of detection with 12 consecutive measurements. Overall, the fabricated sensor showed excellent sensitivity toward Ni(II) and Co(II) in natural water samples.

Microalgal biomass has received much attention as feedstock for biofuel production due to its capacity to accumulate a substantial amount of biocomponents (including lipid, carbohydrate, and protein), high growth rate, and environmental benefit. However, commercial realization of microalgal biofuel is a challenge due to its low biomass production and insufficient technology for complete utilization of biomass. Recently, advanced strategies have been explored to overcome the challenges of conventional approaches and to achieve maximum possible outcomes in terms of growth. These strategies include a combination of stress factors; co-culturing with other microorganisms; and addition of salts, flue gases, and phytohormones. This review summarizes the recent progress in the application of single and combined abiotic stress conditions to stimulate microalgal growth and its biocomponents. An innovative schematic model is presented of the biomass-energy conversion pathway that proposes the transformation of all potential biocomponents of microalgae into biofuels.

Oxygen (O2) is a strong inhibitor of hydrogenase (HydA) activity and expression and altering the sulfur (S) oxidizing transitions in photosystem II (PSII) often allows algal photohydrogen production; however, this may not be practical in a wastewater environment. To counteract natural mechanisms of oxygen evolution in PSII, we utilized acetic acid and butyric acid, which are main volatile fatty acids (VFAs) found in anaerobic bacterial digestion in wastewater treatment, as oxygen regulators for photosynthetic biohydrogen production using Chlorella vulgaris. It was found that a VFA-containing synthetic wastewater promotes oxygen depletion in a photobioreactor (PBR), producing maximum hydrogen yield of 65.4 ± 0.3 μmoL H2 L−1 mM−1 acetate without artificial sulfur or chloride deprivation. Butyric acids showed no significant effect on oxygen depletion and biohydrogen production in the PBR. The measurements of both relative expression level of mRNA and specific activities of reactivate HydA revealed that repetitive algal H2 photo-evolution was possible by HydA synthesis in C. vulgaris followed by complete oxygen depletion controlled by acetic acid levels in the PBR. This emerging understanding of the role of VFAs on oxygen regulation in PSII in natural environments is expected to lead algal-driven bioenergy production technologies to the next level.

In this work, a novel copper-chitosan (Cu-chitosan) nanocomposite-based flexible electrochemical sensor with an integrated Ag/AgCl reference electrode is fabricated. The electrochemical sensor is fabricated using low-cost screen-printing technology on a flexible substrate, followed by the electrochlorination of silver to form an integrated Ag/AgCl reference electrode and electrochemical deposition of a Cu-chitosan nanocomposite film to produce a working electrode. The surface chemical analysis of the working and reference electrodes using XPS (X-ray photoelectron spectroscopy) shows the formation of functional layers. The fabricated Cu-chitosan nanocomposite-based sensors are used to determine the trace level lead (Pb2+) ions in real-world water samples (i.e., tap water, mining wastewater, and soil leachate) using square wave anodic stripping voltammetry (SWSAV). A noticeable peak for lead ions is observed at ∼0.46 V vs. integrated Ag/AgCl reference electrode. The limit of detection (LOD) of the developed flexible electrochemical sensor in tap water is 0.72 ppb with the relative standard deviations (n = 10) of 0.65 %. The fabricated electrochemical sensor exhibits a higher response to lead ions (Pb2+) than the previously reported copper-based electrochemical sensor. These results show that chitosan's presence on the composite material enhances the sensitivity and mechanical flexibility.

Microalgae can offer several benefits for wastewater treatment with their ability to produce large amounts of lipids for biofuel production and the high economic value of harvested biomass for biogas and fertilizer. This study found that salt concentration (∼45gL-1) had more of an effect than salt type on metabolisms of Chlorella vulgaris for wastewater treatment and biofuel production. Salinity stress decreased the algal growth rate in wastewater by 0.003day-1permScm-1 and slightly reduced nutrient removal rates. However, salinity stress was shown to increase total lipid content from 11.5% to 16.1% while also increasing the saturated portions of fatty acids in C. vulgaris. In addition, salinity increased the algal settling rate from 0.06 to 0.11mday-1 which could potentially reduce the cost of harvesting for algal biofuel production. Overall, C. vulgaris makes a suitable candidate for high salinity wastewater cultivation and biofuel production.

Permeate reuse for cultivating Synechocystis sp. PCC 6803 was studied in batch photosynthetic-growth experiments having a wide range of the ratio of membrane permeate to BG-11 medium. The 50% dilution of permeate gave the greatest biomass concentration and specific growth rate for Synechocystis , but up to 100% permeate had minimal impact on biomass growth; thus, a high ratio of permeate supported good growth of Synechocystis . With initial values of the spatially averaged light intensity (LI SA ) ranging from 49 to 479 μE m − 2 s − 1 , Synechocystis exhibited typical photo-inhibition growth kinetics in 50% permeate. The half-maximum-rate light irradiance (K L ) was 39 μE m − 2 s − 1 , and the half-inhibition-rate light irradiance (K I ) was 281 μE m − 2 s − 1 . The K I value is larger than seen previously for Synechocystis in BG-11 medium, which suggests that culturing in permeate may have made Synechocystis less sensitive to photo-inhibition. The exponential growth rate of Synechocystis sp. PCC 6803 was not inhibited by recycled permeate through multiple rounds of growth in 50% permeate. These results demonstrate that permeate recycling is a feasible strategy for reusing nutrients and minimizing water loss.

A novel bismuth (Bi)-biopolymer (chitosan) nanocomposite screen-printed carbon electrode was developed using a Bi and chitosan co-electrodepositing technique for detecting multiple heavy metal ions. The developed sensor was fabricated with environmentally benign materials and processes. In real wastewater, heavy metal detection was evaluated by the developed sensor using square wave anodic stripping voltammetry (SWASV). The nanocomposite sensor showed the detection limit of 0.1 ppb Zn2+, 0.1 ppb Cd2+ and 0.2 ppb Pb2+ in stock solutions. The improved sensitivity of the Bi-chitosan nanocomposite sensor over previously reported Bi nanocomposite sensors was attributed to the role of chitosan. When used for real wastewater samples collected from a mining site and soil leachate, similar detection limit values with 0.4 ppb Cd2+ and 0.3 ppb Pb2+ were obtained with relative standard deviations (RSD) ranging from 1.3% to 5.6% (n = 8). Temperature changes (4 and 23 &deg, C) showed no significant impact on sensor performance. Although Zn2+ in stock solutions was well measured by the sensor, the interference observed while detecting Zn2+ in the presence of Cu2+ was possibly due to the presence of Cu-Zn intermetallic species in mining wastewater. Overall, the developed sensor has the capability of monitoring multiple heavy metals in contaminated water samples without the need for complicated sample preparation or transportation of samples to a laboratory.

Recent advancements in MoS

Microbial fuel cells (MFCs) have recently been applied to generate electricity from oily wastewater. Although MFCs that utilize microalgae to provide a self-supporting oxygen (O(2)) supply at the cathode have been well discussed, those with microalgae at the anode as an active biomass for treating wastewater and producing electrons are still poorly studied and understood. Here, we demonstrated a bilgewater treatment using single- and double-chamber microalgal fuel cells (SMAFC and DMAFC) capable of generating energy with a novel microalgal strain (Chlorella sorokiniana) that was initially isolated from oily wastewater. Compared to previous MFC studies using green algae, relatively high voltage output (151.3–160.1 mV, 71.3–83.4 mV m(−2) of power density) was observed in the SMAFC under O(2) controlled systems (i.e., acetate addition or light/dark cycle). It was assumed that, under the O(2) depletion, alternative electron acceptors such as bicarbonate may be utilized for power generation. A DMAFC showed better power density (up to 23.9%) compared to the SMAFC due to the separated cathode chamber which fully utilizes O(2) as an electron acceptor. Both SMAFC and DMAFC removed 67.2–77.4% of soluble chemical oxygen demands (SCOD) from the synthetic bilgewater. This study demonstrates that the application of algae-based MFCs is a feasible strategy to treat oil-in-water emulsion while generating electricity.

Effect of various flue gas CO2 concentrations (5%, 10% and 14.1%) on growth rate and biochemical properties of a green microalga Scenedesmus obliquus was investigated. S. obliquus showed the highest biomass production and growth rate (0.36 g L−1 and μmax = 1.00 day−1), total inorganic carbon removal (35.8 mg L−1), lipid productivity (9.9 mg L−1 day) and carbohydrate productivity (10.3 mg L−1 day) with 14.1% CO2 after 8 days of cultivation. Fatty acid methyl ester analysis revealed that the palmitic and oleic acid contents were increased up to 5% and 7% with 14.1% CO2, respectively. Application of flue gas CO2 enhanced the growth along with lipid and carbohydrate productivity of S. obliquus, which can be exploited for reducing the CO2 concentration.

The impact of combined sonication, heat and enzyme (SHE) treatment on continuous bioethanol production from mixed microalgal biomass (cyclotella and filamentous) was evaluated in a fermentor. Different pretreatments resulted in varied degrees of cell lysis for microbial fermentation. Filamentous algae were partially damaged under sonication pretreatment, while SHE treatment leads to complete destruction of both cyclotella and filamentous microalgal cells. SHE treatment significantly increased the dissolved carbohydrate concentration (up to 5.8 folds greater than non-pretreated), which enhanced the ethanol production through microbial fermentation. Higher bioactivity of alcohol fermentation by Dekkera bruxellensis (yeast) resulted in higher ethanol yield compared to mixed bacterial culture. The cumulative ethanol production after SHE treatment was 1.4 fold higher than with combined sonication and enzyme (SE) treatment using D. bruxellensis . These results demonstrate that combined SHE treatment is an effective method for the enhancement of yeast promoted fermentative bioethanol production from mixed microalgal biomass.

Per- and poly-fluoroalkyl substances (PFASs) have recently been labeled as toxic constituents that exist in many aqueous environments. However, traditional methods used to determine the level of PFASs are often not appropriate for continuous environmental monitoring and management. Based on the current state of research, PFAS-detecting sensors have surfaced as a promising method of determination. These sensors are an innovative solution with characteristics that allow for in situ, low-cost, and easy-to-use capabilities. This paper presents a comprehensive review of the recent developments in PFAS-detecting sensors, and why the literature on determination methods has shifted in this direction compared to the traditional methods used. PFAS-detecting sensors discussed herein are primarily categorized in terms of the detection mechanism used. The topics covered also include the current limitations, as well as insight on the future direction of PFAS analyses. This paper is expected to be useful for the smart sensing technology development of PFAS detection methods and the associated environmental management best practices in smart cities of the future.

Microalgae species including Chlamydomonas mexicana, Micractinium reisseri, Scenedesmus obliquus and Tribonema aequale were cultivated in batch cultures, and their biochemical composition was determined. C. mexicana showed the highest carbohydrate content of 52.6% and was selected for further study. Sonication pretreatment under optimum conditions (at 40 kHz, 2.2 Kw, 50 °C for 15 min) released 74 ± 2.7 mg g(-1) of total reducing sugars (TRS) of dry cell weight, while the combined sonication and enzymatic hydrolysis treatment enhanced the TRS yield by fourfold (280.5 ± 4.9 mg g(-1)). The optimal ratio of enzyme [E]:substrate [S] for maximum TRS yield was [1]:[5] at 50 °C and pH 5. Combined sonication and hydrolysis treatment released 7.3% (27.1 ± 0.9 mg g(-1)) soluble protein of dry cell weight, and further fermentation of the dissolved carbohydrate fraction enhanced the soluble protein content up to 56% (228.4 mg g(-1)) of total protein content. Scanning and transmission electron microscopic analyses indicated that microalgae cells were significantly disrupted by the combined sonication and enzyme hydrolysis treatment. This study indicates that pretreatment and subsequent fermentation of the microalgal biomass enhance the recovery of carbohydrates and proteins which can be used as feedstocks for generation of biofuels.

In this paper the population fluctuation in the central-western region of the Korean Peninsula is investigated using radiocarbon data obtained from prehistoric pit houses in residential bases or settlements during the seventh to third millennium cal BP comprising the Neolithic, Bronze and Early Iron ages in Korea. Fluctuation in radiocarbon date distribution is compared with summed probability distribution of calibrated dates as well as total numbers of settlements and dwellings arranged in chronological order. Results indicate the appearance of Neolithic and Bronze Age settlements in the early sixth and the late fourth millennium BC each followed by a rapid growth of population with a peak around 5500 and 3000 cal BP. Population decline is identified from 5300, 4900, 4500 cal BP during the Neolithic and 2800 and 2400 cal BP during the Bronze Age. The period between 4500 and 3500 cal BP corresponds with the lowest density of settlements and dwellings. Agricultural villages collapsed 2400–2000 cal BP. The paper suggests the hypothesis that climate change, especially cold or dry climate induced by weak Asian monsoon events, is possibly responsible for the fluctuation of settlements and population in prehistoric Korea.

Microalgal (Micractinium reisseri YSW05) photo-heterotrophic hydrogen production was investigated with using volatile fatty acids (acetate and butyrate) from dark-fermentation effluent. Dilution ratio (effluent: deionized water) of 1:0 at pH 8.0 supported the maximum hydrogen and biomass production, and the highest acetate and butyrate consumption. Microalgal hydrogen production was higher with continuous light condition compared to alternating dark/light cycle. Hydrogen production correlated with both, biomass production and hydrogenase activity under all experimental conditions. Hydrogenase activity and apparent hydrogen production decreased significantly with increasing headspace oxygen. Interestingly substantial hydrogenase activity was observed at almost atmospheric partial pressure of oxygen (19%), indicating that the enzyme could be oxygen tolerant. The present study demonstrated the application of conventional microbial fermentation effluent for microalgae cultivation and hydrogen production, and showed the presence of oxygen tolerant hydrogenase in M. reisseri which might help to establish a novel strategy for biohydrogen technology in atmospheric condition.

The endocrine-disrupting chemical, bisphenol A (BPA) has attracted much attention due to its estrogenic activity and widespread environmental distribution. The toxicity and cellular stresses of BPA to Chlamydomonas mexicana and Chlorella vulgaris and its biodegradation/bioaccumulation by both microalgae were investigated. The 120-h EC 50 of BPA for C. mexicana and C. vulgaris were 44.8 and 39.8 mg L −1 , respectively. The dry cell weight and chlorophyll a content of both microalgae decreased with increasing BPA concentration higher than 10 mg L −1 . Growth of C. vulgaris was significantly inhibited at 50 mg L −1 BPA compared to C . mexicana . Total nitrogen (TN) and total phosphorous (TP) removal was higher in C . mexicana than in C. vulgaris . Microalgae performed the bioaccumulation and biodegradation of BPA to varying extents at different initial BPA concentrations. The highest rates of BPA biodegradation, 24 and 23% by C. mexicana and C. vulgaris , respectively, were achieved at 1 mg L −1 BPA. Both the total fatty acid and carbohydrate contents increased with increasing BPA concentration. This study demonstrated that C. mexicana was more tolerant to BPA and could be used for treatment of BPA contaminated aqueous systems.

The feasibility of perchlorate reducing-bacteria isolated from the sludge of an anaerobic digester was determined using ammonium perchlorate in aqueous medium. Growth kinetics of the two perchlorate reducing bacteria including Rhodococcus sp. YSPW01 and YSPW02 were investigated using acetate as the electron donor in batch experiment. The growth of YSPW01 and YSPW02 reached a steady-state at 26 and 9 h, respectively. The initial perchlorate concentration was completely reduced within 8 and 7 h by YSPW01 and YSPW02, respectively. The reduction rates were 2.1 and 15 mg L -1 h -1 for YSPW01, and 3.2 and 15.5 mg L -1 h -1 for YSPW02, at 1:1 and 5:1 ratios of acetate:perchlorate (w:w), respectively. In this study, the bacteria Rhodococcus sp. YSPW01 and YSPW02 demonstrated a potential for the perchlorate reduction, which could be further investigated for develo-pment of an efficient strategy to treat the perchlorate contaminated waters. Key Words : Ammonium Perchlorate, Perchlorate Reducing Bacteria, Newly Isolated Bacteria, Rhodococcus sp., Batch Experiment

This study evaluated variations in Neochloris oleoabundans' growth rate and biochemical characteristics (fatty acid methyl ester (FAME) profile and lipid granule properties) in response to light-emitting diodes (LEDs) at a range of spatially-averaged light intensities (LISA) in either the red or white spectra. The red-light spectra (630–700 nm) yielded the greatest proportions of total lipids (25.2 ± 0.2 wt%) as well as monounsaturated fatty acids (MUFAs) such as C16:1 and C18:1, producing a high-quality FAMEs profile for biodiesel production. Using white and red spectra, the half-maximum-rate light irradiance (KL) was 35 and 37 μE m−2 s−1 and the half-inhibition-rate light irradiance (KI) was 299 and 502 μE m−2 s−1, respectively. The greater red-light KI value suggests that N. oleoabundans is less sensitive to photoinhibition by light of that spectra. Transmission electron microscope (TEM) images also showed enlarged lipid bodies in algal cells grown under high light intensities in the red spectra, a clear advantage for lipid production. These results demonstrate that control over light wavelength is a powerful tool for the production of high-quality fatty acids in microalgae could be a viable and sustainable medium for algae cultivation.

Piggery effluent is one of the most highly produced wastewaters throughout the world, containing high levels of inorganic nutrient species. In this study, a microalga Scenedesmus obliquus YSW-14 (S. obliquus) was employed not only for nutrient removal from piggery wastewater effluent but also for lipid accumulation in the algal biomass as a feedstock for biofuel production. The piggery wastewater effluent was diluted up to fivefold with synthetic media to reduce the toxicity of (in)organic components, which resulted in improved microalgal growth, nutrient removal, and lipid productivity. Among the examined culture conditions, a 40% concentration of wastewater effluent was found to be most effective for microalga lipid productivity (0.13 mg L−1). S. obliquus removed 155 mg total nitrogen and 4 mg total phosphate per gram of dried algae for growth at the same dilution condition. These results demonstrate the feasibility of using microalgae for advanced wastewater treatment and subsequent production...

Effect of various flue gas CO

Due to increasing oil prices and climate change concerns, biodiesel has gained attention as an alternative energy source. Biodiesel derived from microalgae is a potentially renewable and carbon–neutral alternative to petroleum fuels. One of the most important decisions in obtaining oil from microalgae is the choice of algal species to use. Eight microalgae from a total of 33 isolated cultures were selected based on their morphology and ease of cultivation. Five cultures were isolated from river and identified as strains of Scenedesmus obliquus YSR01, Nitzschia cf. pusilla YSR02, Chlorella ellipsoidea YSR03, S. obliquus YSR04, and S. obliquus YSR05, and three were isolated from wastewater and identified as S. obliquus YSW06, Micractinium pusillum YSW07, and Ourococcus multisporus YSW08, based on LSU rDNA (D1-D2) and ITS sequence analyses. S. obliquus YSR01 reached a growth rate of 1.68 ± 0.28 day−1 at 680nm and a biomass concentration of 1.57 ± 0.67 g dwt L−1, with a high lipid content of 58 ± 1.5%. Under similar environmental conditions, M. pusillum reached a growth rate of 2.3 ± 0.55 day−1 and a biomass concentration of 2.28 ± 0.16 g dwt L−1, with a relatively low lipid content of 24 ± 0.5% w/w. The fatty acid compositions of the studied species were mainly myristic, palmitic, palmitoleic, oleic, linoleic, g-linolenic, and linolenic acids. Our results suggest that S. obliquus YSR01 can be a possible candidate species for producing oils for biodiesel, based on its high lipid and oleic acid contents.

The quantitative relationship between sulfate reducing bacteria (SRB) and hydrogen (H2) production from sulfate (SO42−) and ferrous [Fe(II)] enriched wastewater was investigated. Both Fe(II) (0–11,600 mg/L) and SO42− (0–20,000 mg/L) improved the H2 production efficiency from wastewater. The H2 yields were increased up to 1.9 mol H2/mol glucose in 580–1750 mg Fe(II)/L and 1000–3000 mg SO42−/L enriched wastewater at pH 5.8–6.2. Quantitative Fluorescence In Situ Hybridization (FISH) analyses revealed that the specific sulfate reducing activities (SSRA) were increased from 0.08 and 0.06 to 0.16 and 0.21 g TS/g SRB h in response to variations in sulfate concentration from 300–20,000 mg/L at pH 5.8 and 6.2, respectively. H2 production was not influenced by low SSRA (≤0.1 g TS/g SRB h), which was independent of pH variation. The results demonstrated that the SSRA and Fe(II) concentration can significantly influence on the biological H2 production from SO42− and Fe(II) containing wastewater.

Anaerobic fermentation for hydrogen (H2) production was studied in a two-stage fermentation system fed with different ripened fruit feedstocks (apple, pear, and grape). Among the feedstocks, ripened apple was the most efficient substrate for cumulative H2 production (4463.7 mL-H2 L(-1)-culture) with a maximum H2 yield (2.2 mol H2 mol(-1) glucose) in the first stage at a hydraulic retention time (HRT) of 18 h. The additional cumulative biohydrogen (3337.4 mL-H2 L(-1)-culture) was produced in the second stage with the reused residual substrate from the first stage. The major byproducts in this study were butyrate, acetate, and ethanol, and butyrate was dominant among them in all test runs. During the two-stage system, the energy efficiency (H(2) conversion) obtained from mixed ripened fruits (RF) increased from 4.6% (in the first stage) to 15.5% (in the second stage), which indicated the energy efficiency can be improved by combined hydrogen production process. The RF could be used as substrates for biohydrogen fermentation in a two-stage (dark/dark) fermentation system.